-GDB Internals documentation
+\input texinfo
+@setfilename gdbint.info
-This needs to be wrapped in texinfo stuff...
+@ifinfo
+@format
+START-INFO-DIR-ENTRY
+* Gdb-Internals: (gdbint). The GNU debugger's internals.
+END-INFO-DIR-ENTRY
+@end format
+@end ifinfo
-Cleanups
+@ifinfo
+This file documents the internals of the GNU debugger GDB.
+
+Copyright 1990-1999 Free Software Foundation, Inc.
+Contributed by Cygnus Solutions. Written by John Gilmore.
+Second Edition by Stan Shebs.
+
+Permission is granted to make and distribute verbatim copies of this
+manual provided the copyright notice and this permission notice are
+preserved on all copies.
+
+@ignore
+Permission is granted to process this file through Tex and print the
+results, provided the printed document carries copying permission notice
+identical to this one except for the removal of this paragraph (this
+paragraph not being relevant to the printed manual).
+
+@end ignore
+Permission is granted to copy or distribute modified versions of this
+manual under the terms of the GPL (for which purpose this text may be
+regarded as a program in the language TeX).
+@end ifinfo
+
+@setchapternewpage off
+@settitle GDB Internals
+
+@titlepage
+@title{GDB Internals}
+@subtitle{A guide to the internals of the GNU debugger}
+@author John Gilmore
+@author Cygnus Solutions
+@author Second Edition:
+@author Stan Shebs
+@author Cygnus Solutions
+@page
+@tex
+\def\$#1${{#1}} % Kluge: collect RCS revision info without $...$
+\xdef\manvers{\$Revision$} % For use in headers, footers too
+{\parskip=0pt
+\hfill Cygnus Solutions\par
+\hfill \manvers\par
+\hfill \TeX{}info \texinfoversion\par
+}
+@end tex
+
+@vskip 0pt plus 1filll
+Copyright @copyright{} 1990-1999 Free Software Foundation, Inc.
+
+Permission is granted to make and distribute verbatim copies of
+this manual provided the copyright notice and this permission notice
+are preserved on all copies.
+
+@end titlepage
+
+@node Top
+@c Perhaps this should be the title of the document (but only for info,
+@c not for TeX). Existing GNU manuals seem inconsistent on this point.
+@top Scope of this Document
+
+This document documents the internals of the GNU debugger, GDB. It
+includes description of GDB's key algorithms and operations, as well
+as the mechanisms that adapt GDB to specific hosts and targets.
+
+@menu
+* Requirements::
+* Overall Structure::
+* Algorithms::
+* User Interface::
+* Symbol Handling::
+* Language Support::
+* Host Definition::
+* Target Architecture Definition::
+* Target Vector Definition::
+* Native Debugging::
+* Support Libraries::
+* Coding::
+* Porting GDB::
+* Testsuite::
+* Hints::
+@end menu
+
+@node Requirements
+
+@chapter Requirements
+
+Before diving into the internals, you should understand the formal
+requirements and other expectations for GDB. Although some of these may
+seem obvious, there have been proposals for GDB that have run counter to
+these requirements.
+
+First of all, GDB is a debugger. It's not designed to be a front panel
+for embedded systems. It's not a text editor. It's not a shell. It's
+not a programming environment.
+
+GDB is an interactive tool. Although a batch mode is available, GDB's
+primary role is to interact with a human programmer.
+
+GDB should be responsive to the user. A programmer hot on the trail of
+a nasty bug, and operating under a looming deadline, is going to be very
+impatient of everything, including the response time to debugger
+commands.
+
+GDB should be relatively permissive, such as for expressions. While the
+compiler should be picky (or have the option to be made picky), since
+source code lives for a long time usually, the programmer doing
+debugging shouldn't be spending time figuring out to mollify the
+debugger.
+
+GDB will be called upon to deal with really large programs. Executable
+sizes of 50 to 100 megabytes occur regularly, and we've heard reports of
+programs approaching 1 gigabyte in size.
+
+GDB should be able to run everywhere. No other debugger is available
+for even half as many configurations as GDB supports.
+
+
+@node Overall Structure
+
+@chapter Overall Structure
+
+GDB consists of three major subsystems: user interface, symbol handling
+(the ``symbol side''), and target system handling (the ``target side'').
+
+Ther user interface consists of several actual interfaces, plus
+supporting code.
+
+The symbol side consists of object file readers, debugging info
+interpreters, symbol table management, source language expression
+parsing, type and value printing.
+
+The target side consists of execution control, stack frame analysis, and
+physical target manipulation.
+
+The target side/symbol side division is not formal, and there are a
+number of exceptions. For instance, core file support involves symbolic
+elements (the basic core file reader is in BFD) and target elements (it
+supplies the contents of memory and the values of registers). Instead,
+this division is useful for understanding how the minor subsystems
+should fit together.
+
+@section The Symbol Side
+
+The symbolic side of GDB can be thought of as ``everything you can do in
+GDB without having a live program running''. For instance, you can look
+at the types of variables, and evaluate many kinds of expressions.
+
+@section The Target Side
+
+The target side of GDB is the ``bits and bytes manipulator''. Although
+it may make reference to symbolic info here and there, most of the
+target side will run with only a stripped executable available -- or
+even no executable at all, in remote debugging cases.
+
+Operations such as disassembly, stack frame crawls, and register
+display, are able to work with no symbolic info at all. In some cases,
+such as disassembly, GDB will use symbolic info to present addresses
+relative to symbols rather than as raw numbers, but it will work either
+way.
+
+@section Configurations
+
+@dfn{Host} refers to attributes of the system where GDB runs.
+@dfn{Target} refers to the system where the program being debugged
+executes. In most cases they are the same machine, in which case a
+third type of @dfn{Native} attributes come into play.
+
+Defines and include files needed to build on the host are host support.
+Examples are tty support, system defined types, host byte order, host
+float format.
+
+Defines and information needed to handle the target format are target
+dependent. Examples are the stack frame format, instruction set,
+breakpoint instruction, registers, and how to set up and tear down the stack
+to call a function.
+
+Information that is only needed when the host and target are the same,
+is native dependent. One example is Unix child process support; if the
+host and target are not the same, doing a fork to start the target
+process is a bad idea. The various macros needed for finding the
+registers in the @code{upage}, running @code{ptrace}, and such are all
+in the native-dependent files.
+
+Another example of native-dependent code is support for features that
+are really part of the target environment, but which require
+@code{#include} files that are only available on the host system. Core
+file handling and @code{setjmp} handling are two common cases.
+
+When you want to make GDB work ``native'' on a particular machine, you
+have to include all three kinds of information.
+
+
+@node Algorithms
+
+@chapter Algorithms
+
+GDB uses a number of debugging-specific algorithms. They are often not
+very complicated, but get lost in the thicket of special cases and
+real-world issues. This chapter describes the basic algorithms and
+mentions some of the specific target definitions that they use.
+
+@section Frames
+
+A frame is a construct that GDB uses to keep track of calling and called
+functions.
+
+@code{FRAME_FP} in the machine description has no meaning to the
+machine-independent part of GDB, except that it is used when setting up
+a new frame from scratch, as follows:
+
+@example
+ create_new_frame (read_register (FP_REGNUM), read_pc ()));
+@end example
+
+Other than that, all the meaning imparted to @code{FP_REGNUM} is
+imparted by the machine-dependent code. So, @code{FP_REGNUM} can have
+any value that is convenient for the code that creates new frames.
+(@code{create_new_frame} calls @code{INIT_EXTRA_FRAME_INFO} if it is
+defined; that is where you should use the @code{FP_REGNUM} value, if
+your frames are nonstandard.)
+
+Given a GDB frame, define @code{FRAME_CHAIN} to determine the address of
+the calling function's frame. This will be used to create a new GDB
+frame struct, and then @code{INIT_EXTRA_FRAME_INFO} and
+@code{INIT_FRAME_PC} will be called for the new frame.
+
+@section Breakpoint Handling
+
+In general, a breakpoint is a user-designated location in the program
+where the user wants to regain control if program execution ever reaches
+that location.
+
+There are two main ways to implement breakpoints; either as ``hardware''
+breakpoints or as ``software'' breakpoints.
+
+Hardware breakpoints are sometimes available as a builtin debugging
+features with some chips. Typically these work by having dedicated
+register into which the breakpoint address may be stored. If the PC
+ever matches a value in a breakpoint registers, the CPU raises an
+exception and reports it to GDB. Another possibility is when an
+emulator is in use; many emulators include circuitry that watches the
+address lines coming out from the processor, and force it to stop if the
+address matches a breakpoint's address. A third possibility is that the
+target already has the ability to do breakpoints somehow; for instance,
+a ROM monitor may do its own software breakpoints. So although these
+are not literally ``hardware breakpoints'', from GDB's point of view
+they work the same; GDB need not do nothing more than set the breakpoint
+and wait for something to happen.
+
+Since they depend on hardware resources, hardware breakpoints may be
+limited in number; when the user asks for more, GDB will start trying to
+set software breakpoints.
+
+Software breakpoints require GDB to do somewhat more work. The basic
+theory is that GDB will replace a program instruction with a trap,
+illegal divide, or some other instruction that will cause an exception,
+and then when it's encountered, GDB will take the exception and stop the
+program. When the user says to continue, GDB will restore the original
+instruction, single-step, re-insert the trap, and continue on.
+
+Since it literally overwrites the program being tested, the program area
+must be writeable, so this technique won't work on programs in ROM. It
+can also distort the behavior of programs that examine themselves,
+although the situation would be highly unusual.
+
+Also, the software breakpoint instruction should be the smallest size of
+instruction, so it doesn't overwrite an instruction that might be a jump
+target, and cause disaster when the program jumps into the middle of the
+breakpoint instruction. (Strictly speaking, the breakpoint must be no
+larger than the smallest interval between instructions that may be jump
+targets; perhaps there is an architecture where only even-numbered
+instructions may jumped to.) Note that it's possible for an instruction
+set not to have any instructions usable for a software breakpoint,
+although in practice only the ARC has failed to define such an
+instruction.
+
+The basic definition of the software breakpoint is the macro
+@code{BREAKPOINT}.
+
+Basic breakpoint object handling is in @file{breakpoint.c}. However,
+much of the interesting breakpoint action is in @file{infrun.c}.
+
+@section Single Stepping
+
+@section Signal Handling
+
+@section Thread Handling
+
+@section Inferior Function Calls
+
+@section Longjmp Support
+
+GDB has support for figuring out that the target is doing a
+@code{longjmp} and for stopping at the target of the jump, if we are
+stepping. This is done with a few specialized internal breakpoints,
+which are visible in the @code{maint info breakpoint} command.
+
+To make this work, you need to define a macro called
+@code{GET_LONGJMP_TARGET}, which will examine the @code{jmp_buf}
+structure and extract the longjmp target address. Since @code{jmp_buf}
+is target specific, you will need to define it in the appropriate
+@file{tm-@var{xyz}.h} file. Look in @file{tm-sun4os4.h} and
+@file{sparc-tdep.c} for examples of how to do this.
+
+@node User Interface
+
+@chapter User Interface
+
+GDB has several user interfaces. Although the command-line interface
+is the most common and most familiar, there are others.
+
+@section Command Interpreter
+
+The command interpreter in GDB is fairly simple. It is designed to
+allow for the set of commands to be augmented dynamically, and also
+has a recursive subcommand capability, where the first argument to
+a command may itself direct a lookup on a different command list.
+
+For instance, the @code{set} command just starts a lookup on the
+@code{setlist} command list, while @code{set thread} recurses
+to the @code{set_thread_cmd_list}.
+
+To add commands in general, use @code{add_cmd}. @code{add_com} adds to
+the main command list, and should be used for those commands. The usual
+place to add commands is in the @code{_initialize_@var{xyz}} routines at the
+ends of most source files.
+
+@section Console Printing
+
+@section TUI
+
+@section libgdb
+
+@code{libgdb} was an abortive project of years ago. The theory was to
+provide an API to GDB's functionality.
+
+@node Symbol Handling
+
+@chapter Symbol Handling
+
+Symbols are a key part of GDB's operation. Symbols include variables,
+functions, and types.
+
+@section Symbol Reading
+
+GDB reads symbols from ``symbol files''. The usual symbol file is the
+file containing the program which GDB is debugging. GDB can be directed
+to use a different file for symbols (with the @code{symbol-file}
+command), and it can also read more symbols via the ``add-file'' and
+``load'' commands, or while reading symbols from shared libraries.
+
+Symbol files are initially opened by code in @file{symfile.c} using the
+BFD library. BFD identifies the type of the file by examining its
+header. @code{find_sym_fns} then uses this identification to locate a
+set of symbol-reading functions.
+
+Symbol reading modules identify themselves to GDB by calling
+@code{add_symtab_fns} during their module initialization. The argument
+to @code{add_symtab_fns} is a @code{struct sym_fns} which contains the
+name (or name prefix) of the symbol format, the length of the prefix,
+and pointers to four functions. These functions are called at various
+times to process symbol-files whose identification matches the specified
+prefix.
+
+The functions supplied by each module are:
+
+@table @code
+@item @var{xyz}_symfile_init(struct sym_fns *sf)
+
+Called from @code{symbol_file_add} when we are about to read a new
+symbol file. This function should clean up any internal state (possibly
+resulting from half-read previous files, for example) and prepare to
+read a new symbol file. Note that the symbol file which we are reading
+might be a new "main" symbol file, or might be a secondary symbol file
+whose symbols are being added to the existing symbol table.
+
+The argument to @code{@var{xyz}_symfile_init} is a newly allocated
+@code{struct sym_fns} whose @code{bfd} field contains the BFD for the
+new symbol file being read. Its @code{private} field has been zeroed,
+and can be modified as desired. Typically, a struct of private
+information will be @code{malloc}'d, and a pointer to it will be placed
+in the @code{private} field.
+
+There is no result from @code{@var{xyz}_symfile_init}, but it can call
+@code{error} if it detects an unavoidable problem.
+
+@item @var{xyz}_new_init()
+
+Called from @code{symbol_file_add} when discarding existing symbols.
+This function need only handle the symbol-reading module's internal
+state; the symbol table data structures visible to the rest of GDB will
+be discarded by @code{symbol_file_add}. It has no arguments and no
+result. It may be called after @code{@var{xyz}_symfile_init}, if a new
+symbol table is being read, or may be called alone if all symbols are
+simply being discarded.
+
+@item @var{xyz}_symfile_read(struct sym_fns *sf, CORE_ADDR addr, int mainline)
+
+Called from @code{symbol_file_add} to actually read the symbols from a
+symbol-file into a set of psymtabs or symtabs.
+
+@code{sf} points to the struct sym_fns originally passed to
+@code{@var{xyz}_sym_init} for possible initialization. @code{addr} is
+the offset between the file's specified start address and its true
+address in memory. @code{mainline} is 1 if this is the main symbol
+table being read, and 0 if a secondary symbol file (e.g. shared library
+or dynamically loaded file) is being read.@refill
+@end table
+
+In addition, if a symbol-reading module creates psymtabs when
+@var{xyz}_symfile_read is called, these psymtabs will contain a pointer
+to a function @code{@var{xyz}_psymtab_to_symtab}, which can be called
+from any point in the GDB symbol-handling code.
+
+@table @code
+@item @var{xyz}_psymtab_to_symtab (struct partial_symtab *pst)
+
+Called from @code{psymtab_to_symtab} (or the PSYMTAB_TO_SYMTAB macro) if
+the psymtab has not already been read in and had its @code{pst->symtab}
+pointer set. The argument is the psymtab to be fleshed-out into a
+symtab. Upon return, pst->readin should have been set to 1, and
+pst->symtab should contain a pointer to the new corresponding symtab, or
+zero if there were no symbols in that part of the symbol file.
+@end table
+
+@section Partial Symbol Tables
+
+GDB has three types of symbol tables.
+
+@itemize @bullet
+
+@item full symbol tables (symtabs). These contain the main information
+about symbols and addresses.
+
+@item partial symbol tables (psymtabs). These contain enough
+information to know when to read the corresponding part of the full
+symbol table.
+
+@item minimal symbol tables (msymtabs). These contain information
+gleaned from non-debugging symbols.
+
+@end itemize
+
+This section describes partial symbol tables.
+
+A psymtab is constructed by doing a very quick pass over an executable
+file's debugging information. Small amounts of information are
+extracted -- enough to identify which parts of the symbol table will
+need to be re-read and fully digested later, when the user needs the
+information. The speed of this pass causes GDB to start up very
+quickly. Later, as the detailed rereading occurs, it occurs in small
+pieces, at various times, and the delay therefrom is mostly invisible to
+the user.
+@c (@xref{Symbol Reading}.)
+
+The symbols that show up in a file's psymtab should be, roughly, those
+visible to the debugger's user when the program is not running code from
+that file. These include external symbols and types, static symbols and
+types, and enum values declared at file scope.
+
+The psymtab also contains the range of instruction addresses that the
+full symbol table would represent.
+
+The idea is that there are only two ways for the user (or much of the
+code in the debugger) to reference a symbol:
+
+@itemize @bullet
+
+@item by its address
+(e.g. execution stops at some address which is inside a function in this
+file). The address will be noticed to be in the range of this psymtab,
+and the full symtab will be read in. @code{find_pc_function},
+@code{find_pc_line}, and other @code{find_pc_@dots{}} functions handle
+this.
+
+@item by its name
+(e.g. the user asks to print a variable, or set a breakpoint on a
+function). Global names and file-scope names will be found in the
+psymtab, which will cause the symtab to be pulled in. Local names will
+have to be qualified by a global name, or a file-scope name, in which
+case we will have already read in the symtab as we evaluated the
+qualifier. Or, a local symbol can be referenced when we are "in" a
+local scope, in which case the first case applies. @code{lookup_symbol}
+does most of the work here.
+
+@end itemize
+
+The only reason that psymtabs exist is to cause a symtab to be read in
+at the right moment. Any symbol that can be elided from a psymtab,
+while still causing that to happen, should not appear in it. Since
+psymtabs don't have the idea of scope, you can't put local symbols in
+them anyway. Psymtabs don't have the idea of the type of a symbol,
+either, so types need not appear, unless they will be referenced by
+name.
+
+It is a bug for GDB to behave one way when only a psymtab has been read,
+and another way if the corresponding symtab has been read in. Such bugs
+are typically caused by a psymtab that does not contain all the visible
+symbols, or which has the wrong instruction address ranges.
+
+The psymtab for a particular section of a symbol-file (objfile) could be
+thrown away after the symtab has been read in. The symtab should always
+be searched before the psymtab, so the psymtab will never be used (in a
+bug-free environment). Currently, psymtabs are allocated on an obstack,
+and all the psymbols themselves are allocated in a pair of large arrays
+on an obstack, so there is little to be gained by trying to free them
+unless you want to do a lot more work.
+
+@section Types
+
+Fundamental Types (e.g., FT_VOID, FT_BOOLEAN).
+
+These are the fundamental types that GDB uses internally. Fundamental
+types from the various debugging formats (stabs, ELF, etc) are mapped
+into one of these. They are basically a union of all fundamental types
+that gdb knows about for all the languages that GDB knows about.
+
+Type Codes (e.g., TYPE_CODE_PTR, TYPE_CODE_ARRAY).
+
+Each time GDB builds an internal type, it marks it with one of these
+types. The type may be a fundamental type, such as TYPE_CODE_INT, or a
+derived type, such as TYPE_CODE_PTR which is a pointer to another type.
+Typically, several FT_* types map to one TYPE_CODE_* type, and are
+distinguished by other members of the type struct, such as whether the
+type is signed or unsigned, and how many bits it uses.
+
+Builtin Types (e.g., builtin_type_void, builtin_type_char).
+
+These are instances of type structs that roughly correspond to
+fundamental types and are created as global types for GDB to use for
+various ugly historical reasons. We eventually want to eliminate these.
+Note for example that builtin_type_int initialized in gdbtypes.c is
+basically the same as a TYPE_CODE_INT type that is initialized in
+c-lang.c for an FT_INTEGER fundamental type. The difference is that the
+builtin_type is not associated with any particular objfile, and only one
+instance exists, while c-lang.c builds as many TYPE_CODE_INT types as
+needed, with each one associated with some particular objfile.
+
+@section Object File Formats
+
+@subsection a.out
+
+The @file{a.out} format is the original file format for Unix. It
+consists of three sections: text, data, and bss, which are for program
+code, initialized data, and uninitialized data, respectively.
+
+The @file{a.out} format is so simple that it doesn't have any reserved
+place for debugging information. (Hey, the original Unix hackers used
+@file{adb}, which is a machine-language debugger.) The only debugging
+format for @file{a.out} is stabs, which is encoded as a set of normal
+symbols with distinctive attributes.
+
+The basic @file{a.out} reader is in @file{dbxread.c}.
+
+@subsection COFF
+
+The COFF format was introduced with System V Release 3 (SVR3) Unix.
+COFF files may have multiple sections, each prefixed by a header. The
+number of sections is limited.
+
+The COFF specification includes support for debugging. Although this
+was a step forward, the debugging information was woefully limited. For
+instance, it was not possible to represent code that came from an
+included file.
+
+The COFF reader is in @file{coffread.c}.
+
+@subsection ECOFF
+
+ECOFF is an extended COFF originally introduced for Mips and Alpha
+workstations.
+
+The basic ECOFF reader is in @file{mipsread.c}.
+
+@subsection XCOFF
+
+The IBM RS/6000 running AIX uses an object file format called XCOFF.
+The COFF sections, symbols, and line numbers are used, but debugging
+symbols are dbx-style stabs whose strings are located in the
+@samp{.debug} section (rather than the string table). For more
+information, see @xref{Top,,,stabs,The Stabs Debugging Format}.
+
+The shared library scheme has a clean interface for figuring out what
+shared libraries are in use, but the catch is that everything which
+refers to addresses (symbol tables and breakpoints at least) needs to be
+relocated for both shared libraries and the main executable. At least
+using the standard mechanism this can only be done once the program has
+been run (or the core file has been read).
+
+@subsection PE
+
+Windows 95 and NT use the PE (Portable Executable) format for their
+executables. PE is basically COFF with additional headers.
+
+While BFD includes special PE support, GDB needs only the basic
+COFF reader.
+
+@subsection ELF
+
+The ELF format came with System V Release 4 (SVR4) Unix. ELF is similar
+to COFF in being organized into a number of sections, but it removes
+many of COFF's limitations.
+
+The basic ELF reader is in @file{elfread.c}.
+
+@subsection SOM
+
+SOM is HP's object file and debug format (not to be confused with IBM's
+SOM, which is a cross-language ABI).
+
+The SOM reader is in @file{hpread.c}.
+
+@subsection Other File Formats
+
+Other file formats that have been supported by GDB include Netware
+Loadable Modules (@file{nlmread.c}.
+
+@section Debugging File Formats
+
+This section describes characteristics of debugging information that
+are independent of the object file format.
+
+@subsection stabs
+
+@code{stabs} started out as special symbols within the @code{a.out}
+format. Since then, it has been encapsulated into other file
+formats, such as COFF and ELF.
+
+While @file{dbxread.c} does some of the basic stab processing,
+including for encapsulated versions, @file{stabsread.c} does
+the real work.
+
+@subsection COFF
+
+The basic COFF definition includes debugging information. The level
+of support is minimal and non-extensible, and is not often used.
+
+@subsection Mips debug (Third Eye)
+
+ECOFF includes a definition of a special debug format.
+
+The file @file{mdebugread.c} implements reading for this format.
+
+@subsection DWARF 1
+
+DWARF 1 is a debugging format that was originally designed to be
+used with ELF in SVR4 systems.
+
+@c CHILL_PRODUCER
+@c GCC_PRODUCER
+@c GPLUS_PRODUCER
+@c LCC_PRODUCER
+@c If defined, these are the producer strings in a DWARF 1 file. All of
+@c these have reasonable defaults already.
+
+The DWARF 1 reader is in @file{dwarfread.c}.
+
+@subsection DWARF 2
+
+DWARF 2 is an improved but incompatible version of DWARF 1.
+
+The DWARF 2 reader is in @file{dwarf2read.c}.
+
+@subsection SOM
+
+Like COFF, the SOM definition includes debugging information.
+
+@section Adding a New Symbol Reader to GDB
+
+If you are using an existing object file format (a.out, COFF, ELF, etc),
+there is probably little to be done.
+
+If you need to add a new object file format, you must first add it to
+BFD. This is beyond the scope of this document.
+
+You must then arrange for the BFD code to provide access to the
+debugging symbols. Generally GDB will have to call swapping routines
+from BFD and a few other BFD internal routines to locate the debugging
+information. As much as possible, GDB should not depend on the BFD
+internal data structures.
+
+For some targets (e.g., COFF), there is a special transfer vector used
+to call swapping routines, since the external data structures on various
+platforms have different sizes and layouts. Specialized routines that
+will only ever be implemented by one object file format may be called
+directly. This interface should be described in a file
+@file{bfd/libxyz.h}, which is included by GDB.
+
+
+@node Language Support
+
+@chapter Language Support
+
+GDB's language support is mainly driven by the symbol reader, although
+it is possible for the user to set the source language manually.
+
+GDB chooses the source language by looking at the extension of the file
+recorded in the debug info; @code{.c} means C, @code{.f} means Fortran,
+etc. It may also use a special-purpose language identifier if the debug
+format supports it, such as DWARF.
+
+@section Adding a Source Language to GDB
+
+To add other languages to GDB's expression parser, follow the following
+steps:
+
+@table @emph
+@item Create the expression parser.
+
+This should reside in a file @file{@var{lang}-exp.y}. Routines for
+building parsed expressions into a @samp{union exp_element} list are in
+@file{parse.c}.
+
+Since we can't depend upon everyone having Bison, and YACC produces
+parsers that define a bunch of global names, the following lines
+@emph{must} be included at the top of the YACC parser, to prevent the
+various parsers from defining the same global names:
+
+@example
+#define yyparse @var{lang}_parse
+#define yylex @var{lang}_lex
+#define yyerror @var{lang}_error
+#define yylval @var{lang}_lval
+#define yychar @var{lang}_char
+#define yydebug @var{lang}_debug
+#define yypact @var{lang}_pact
+#define yyr1 @var{lang}_r1
+#define yyr2 @var{lang}_r2
+#define yydef @var{lang}_def
+#define yychk @var{lang}_chk
+#define yypgo @var{lang}_pgo
+#define yyact @var{lang}_act
+#define yyexca @var{lang}_exca
+#define yyerrflag @var{lang}_errflag
+#define yynerrs @var{lang}_nerrs
+@end example
+
+At the bottom of your parser, define a @code{struct language_defn} and
+initialize it with the right values for your language. Define an
+@code{initialize_@var{lang}} routine and have it call
+@samp{add_language(@var{lang}_language_defn)} to tell the rest of GDB
+that your language exists. You'll need some other supporting variables
+and functions, which will be used via pointers from your
+@code{@var{lang}_language_defn}. See the declaration of @code{struct
+language_defn} in @file{language.h}, and the other @file{*-exp.y} files,
+for more information.
+
+@item Add any evaluation routines, if necessary
+
+If you need new opcodes (that represent the operations of the language),
+add them to the enumerated type in @file{expression.h}. Add support
+code for these operations in @code{eval.c:evaluate_subexp()}. Add cases
+for new opcodes in two functions from @file{parse.c}:
+@code{prefixify_subexp()} and @code{length_of_subexp()}. These compute
+the number of @code{exp_element}s that a given operation takes up.
+
+@item Update some existing code
+
+Add an enumerated identifier for your language to the enumerated type
+@code{enum language} in @file{defs.h}.
+
+Update the routines in @file{language.c} so your language is included.
+These routines include type predicates and such, which (in some cases)
+are language dependent. If your language does not appear in the switch
+statement, an error is reported.
+
+Also included in @file{language.c} is the code that updates the variable
+@code{current_language}, and the routines that translate the
+@code{language_@var{lang}} enumerated identifier into a printable
+string.
+
+Update the function @code{_initialize_language} to include your
+language. This function picks the default language upon startup, so is
+dependent upon which languages that GDB is built for.
+
+Update @code{allocate_symtab} in @file{symfile.c} and/or symbol-reading
+code so that the language of each symtab (source file) is set properly.
+This is used to determine the language to use at each stack frame level.
+Currently, the language is set based upon the extension of the source
+file. If the language can be better inferred from the symbol
+information, please set the language of the symtab in the symbol-reading
+code.
+
+Add helper code to @code{expprint.c:print_subexp()} to handle any new
+expression opcodes you have added to @file{expression.h}. Also, add the
+printed representations of your operators to @code{op_print_tab}.
+
+@item Add a place of call
+
+Add a call to @code{@var{lang}_parse()} and @code{@var{lang}_error} in
+@code{parse.c:parse_exp_1()}.
+
+@item Use macros to trim code
+
+The user has the option of building GDB for some or all of the
+languages. If the user decides to build GDB for the language
+@var{lang}, then every file dependent on @file{language.h} will have the
+macro @code{_LANG_@var{lang}} defined in it. Use @code{#ifdef}s to
+leave out large routines that the user won't need if he or she is not
+using your language.
+
+Note that you do not need to do this in your YACC parser, since if GDB
+is not build for @var{lang}, then @file{@var{lang}-exp.tab.o} (the
+compiled form of your parser) is not linked into GDB at all.
+
+See the file @file{configure.in} for how GDB is configured for different
+languages.
+
+@item Edit @file{Makefile.in}
+
+Add dependencies in @file{Makefile.in}. Make sure you update the macro
+variables such as @code{HFILES} and @code{OBJS}, otherwise your code may
+not get linked in, or, worse yet, it may not get @code{tar}red into the
+distribution!
+
+@end table
+
+
+@node Host Definition
+
+@chapter Host Definition
+
+With the advent of autoconf, it's rarely necessary to have host
+definition machinery anymore.
+
+@section Adding a New Host
+
+Most of GDB's host configuration support happens via autoconf. It
+should be rare to need new host-specific definitions. GDB still uses
+the host-specific definitions and files listed below, but these mostly
+exist for historical reasons, and should eventually disappear.
+
+Several files control GDB's configuration for host systems:
+
+@table @file
+
+@item gdb/config/@var{arch}/@var{xyz}.mh
+Specifies Makefile fragments needed when hosting on machine @var{xyz}.
+In particular, this lists the required machine-dependent object files,
+by defining @samp{XDEPFILES=@dots{}}. Also specifies the header file
+which describes host @var{xyz}, by defining @code{XM_FILE=
+xm-@var{xyz}.h}. You can also define @code{CC}, @code{SYSV_DEFINE},
+@code{XM_CFLAGS}, @code{XM_ADD_FILES}, @code{XM_CLIBS}, @code{XM_CDEPS},
+etc.; see @file{Makefile.in}.
+
+@item gdb/config/@var{arch}/xm-@var{xyz}.h
+(@file{xm.h} is a link to this file, created by configure). Contains C
+macro definitions describing the host system environment, such as byte
+order, host C compiler and library.
+
+@item gdb/@var{xyz}-xdep.c
+Contains any miscellaneous C code required for this machine as a host.
+On most machines it doesn't exist at all. If it does exist, put
+@file{@var{xyz}-xdep.o} into the @code{XDEPFILES} line in
+@file{gdb/config/@var{arch}/@var{xyz}.mh}.
+
+@end table
+
+@subheading Generic Host Support Files
+
+There are some ``generic'' versions of routines that can be used by
+various systems. These can be customized in various ways by macros
+defined in your @file{xm-@var{xyz}.h} file. If these routines work for
+the @var{xyz} host, you can just include the generic file's name (with
+@samp{.o}, not @samp{.c}) in @code{XDEPFILES}.
+
+Otherwise, if your machine needs custom support routines, you will need
+to write routines that perform the same functions as the generic file.
+Put them into @code{@var{xyz}-xdep.c}, and put @code{@var{xyz}-xdep.o}
+into @code{XDEPFILES}.
+
+@table @file
+
+@item ser-unix.c
+This contains serial line support for Unix systems. This is always
+included, via the makefile variable @code{SER_HARDWIRE}; override this
+variable in the @file{.mh} file to avoid it.
+
+@item ser-go32.c
+This contains serial line support for 32-bit programs running under DOS,
+using the GO32 execution environment.
+
+@item ser-tcp.c
+This contains generic TCP support using sockets.
+
+@end table
+
+@section Host Conditionals
+
+When GDB is configured and compiled, various macros are defined or left
+undefined, to control compilation based on the attributes of the host
+system. These macros and their meanings (or if the meaning is not
+documented here, then one of the source files where they are used is
+indicated) are:
+
+@table @code
+
+@item GDBINIT_FILENAME
+The default name of GDB's initialization file (normally @file{.gdbinit}).
+
+@item MEM_FNS_DECLARED
+Your host config file defines this if it includes declarations of
+@code{memcpy} and @code{memset}. Define this to avoid conflicts between
+the native include files and the declarations in @file{defs.h}.
+
+@item NO_STD_REGS
+This macro is deprecated.
+
+@item NO_SYS_FILE
+Define this if your system does not have a @code{<sys/file.h>}.
+
+@item SIGWINCH_HANDLER
+If your host defines @code{SIGWINCH}, you can define this to be the name
+of a function to be called if @code{SIGWINCH} is received.
+
+@item SIGWINCH_HANDLER_BODY
+Define this to expand into code that will define the function named by
+the expansion of @code{SIGWINCH_HANDLER}.
+
+@item ALIGN_STACK_ON_STARTUP
+Define this if your system is of a sort that will crash in
+@code{tgetent} if the stack happens not to be longword-aligned when
+@code{main} is called. This is a rare situation, but is known to occur
+on several different types of systems.
+
+@item CRLF_SOURCE_FILES
+Define this if host files use @code{\r\n} rather than @code{\n} as a
+line terminator. This will cause source file listings to omit @code{\r}
+characters when printing and it will allow \r\n line endings of files
+which are "sourced" by gdb. It must be possible to open files in binary
+mode using @code{O_BINARY} or, for fopen, @code{"rb"}.
+
+@item DEFAULT_PROMPT
+The default value of the prompt string (normally @code{"(gdb) "}).
+
+@item DEV_TTY
+The name of the generic TTY device, defaults to @code{"/dev/tty"}.
+
+@item FCLOSE_PROVIDED
+Define this if the system declares @code{fclose} in the headers included
+in @code{defs.h}. This isn't needed unless your compiler is unusually
+anal.
+
+@item FOPEN_RB
+Define this if binary files are opened the same way as text files.
+
+@item GETENV_PROVIDED
+Define this if the system declares @code{getenv} in its headers included
+in @code{defs.h}. This isn't needed unless your compiler is unusually
+anal.
+
+@item HAVE_MMAP
+In some cases, use the system call @code{mmap} for reading symbol
+tables. For some machines this allows for sharing and quick updates.
+
+@item HAVE_SIGSETMASK
+Define this if the host system has job control, but does not define
+@code{sigsetmask()}. Currently, this is only true of the RS/6000.
+
+@item HAVE_TERMIO
+Define this if the host system has @code{termio.h}.
+
+@item HOST_BYTE_ORDER
+The ordering of bytes in the host. This must be defined to be either
+@code{BIG_ENDIAN} or @code{LITTLE_ENDIAN}.
+
+@item INT_MAX
+@item INT_MIN
+@item LONG_MAX
+@item UINT_MAX
+@item ULONG_MAX
+Values for host-side constants.
+
+@item ISATTY
+Substitute for isatty, if not available.
+
+@item LONGEST
+This is the longest integer type available on the host. If not defined,
+it will default to @code{long long} or @code{long}, depending on
+@code{CC_HAS_LONG_LONG}.
+
+@item CC_HAS_LONG_LONG
+Define this if the host C compiler supports ``long long''. This is set
+by the configure script.
+
+@item PRINTF_HAS_LONG_LONG
+Define this if the host can handle printing of long long integers via
+the printf format directive ``ll''. This is set by the configure script.
+
+@item HAVE_LONG_DOUBLE
+Define this if the host C compiler supports ``long double''. This is
+set by the configure script.
+
+@item PRINTF_HAS_LONG_DOUBLE
+Define this if the host can handle printing of long double float-point
+numbers via the printf format directive ``Lg''. This is set by the
+configure script.
+
+@item SCANF_HAS_LONG_DOUBLE
+Define this if the host can handle the parsing of long double
+float-point numbers via the scanf format directive directive
+``Lg''. This is set by the configure script.
+
+@item LSEEK_NOT_LINEAR
+Define this if @code{lseek (n)} does not necessarily move to byte number
+@code{n} in the file. This is only used when reading source files. It
+is normally faster to define @code{CRLF_SOURCE_FILES} when possible.
+
+@item L_SET
+This macro is used as the argument to lseek (or, most commonly,
+bfd_seek). FIXME, should be replaced by SEEK_SET instead, which is the
+POSIX equivalent.
+
+@item MALLOC_INCOMPATIBLE
+Define this if the system's prototype for @code{malloc} differs from the
+@sc{ANSI} definition.
+
+@item MMAP_BASE_ADDRESS
+When using HAVE_MMAP, the first mapping should go at this address.
+
+@item MMAP_INCREMENT
+when using HAVE_MMAP, this is the increment between mappings.
+
+@item NEED_POSIX_SETPGID
+Define this to use the POSIX version of @code{setpgid} to determine
+whether job control is available.
+
+@item NORETURN
+If defined, this should be one or more tokens, such as @code{volatile},
+that can be used in both the declaration and definition of functions to
+indicate that they never return. The default is already set correctly
+if compiling with GCC. This will almost never need to be defined.
+
+@item ATTR_NORETURN
+If defined, this should be one or more tokens, such as
+@code{__attribute__ ((noreturn))}, that can be used in the declarations
+of functions to indicate that they never return. The default is already
+set correctly if compiling with GCC. This will almost never need to be
+defined.
+
+@item USE_GENERIC_DUMMY_FRAMES
+Define this to 1 if the target is using the generic inferior function
+call code. See @code{blockframe.c} for more information.
+
+@item USE_MMALLOC
+GDB will use the @code{mmalloc} library for memory allocation for symbol
+reading if this symbol is defined. Be careful defining it since there
+are systems on which @code{mmalloc} does not work for some reason. One
+example is the DECstation, where its RPC library can't cope with our
+redefinition of @code{malloc} to call @code{mmalloc}. When defining
+@code{USE_MMALLOC}, you will also have to set @code{MMALLOC} in the
+Makefile, to point to the mmalloc library. This define is set when you
+configure with --with-mmalloc.
+
+@item NO_MMCHECK
+Define this if you are using @code{mmalloc}, but don't want the overhead
+of checking the heap with @code{mmcheck}. Note that on some systems,
+the C runtime makes calls to malloc prior to calling @code{main}, and if
+@code{free} is ever called with these pointers after calling
+@code{mmcheck} to enable checking, a memory corruption abort is certain
+to occur. These systems can still use mmalloc, but must define
+NO_MMCHECK.
+
+@item MMCHECK_FORCE
+Define this to 1 if the C runtime allocates memory prior to
+@code{mmcheck} being called, but that memory is never freed so we don't
+have to worry about it triggering a memory corruption abort. The
+default is 0, which means that @code{mmcheck} will only install the heap
+checking functions if there has not yet been any memory allocation
+calls, and if it fails to install the functions, gdb will issue a
+warning. This is currently defined if you configure using
+--with-mmalloc.
+
+@item NO_SIGINTERRUPT
+Define this to indicate that siginterrupt() is not available.
+
+@item R_OK
+Define if this is not in a system .h file.
+
+@item SEEK_CUR
+@item SEEK_SET
+Define these to appropriate value for the system lseek(), if not already
+defined.
+
+@item STOP_SIGNAL
+This is the signal for stopping GDB. Defaults to SIGTSTP. (Only
+redefined for the Convex.)
+
+@item USE_O_NOCTTY
+Define this if the interior's tty should be opened with the O_NOCTTY
+flag. (FIXME: This should be a native-only flag, but @file{inflow.c} is
+always linked in.)
+
+@item USG
+Means that System V (prior to SVR4) include files are in use. (FIXME:
+This symbol is abused in @file{infrun.c}, @file{regex.c},
+@file{remote-nindy.c}, and @file{utils.c} for other things, at the
+moment.)
+
+@item lint
+Define this to help placate lint in some situations.
+
+@item volatile
+Define this to override the defaults of @code{__volatile__} or
+@code{/**/}.
+
+@end table
+
+
+@node Target Architecture Definition
+
+@chapter Target Architecture Definition
+
+GDB's target architecture defines what sort of machine-language programs
+GDB can work with, and how it works with them.
+
+At present, the target architecture definition consists of a number of C
+macros.
+
+@section Registers and Memory
+
+GDB's model of the target machine is rather simple. GDB assumes the
+machine includes a bank of registers and a block of memory. Each
+register may have a different size.
+
+GDB does not have a magical way to match up with the compiler's idea of
+which registers are which; however, it is critical that they do match up
+accurately. The only way to make this work is to get accurate
+information about the order that the compiler uses, and to reflect that
+in the @code{REGISTER_NAME} and related macros.
+
+GDB can handle big-endian, little-endian, and bi-endian architectures.
+
+@section Frame Interpretation
+
+@section Inferior Call Setup
+
+@section Compiler Characteristics
+
+@section Target Conditionals
+
+This section describes the macros that you can use to define the target
+machine.
+
+@table @code
+
+@item ADDITIONAL_OPTIONS
+@item ADDITIONAL_OPTION_CASES
+@item ADDITIONAL_OPTION_HANDLER
+@item ADDITIONAL_OPTION_HELP
+These are a set of macros that allow the addition of additional command
+line options to GDB. They are currently used only for the unsupported
+i960 Nindy target, and should not be used in any other configuration.
+
+@item ADDR_BITS_REMOVE (addr)
+If a raw machine instruction address includes any bits that are not
+really part of the address, then define this macro to expand into an
+expression that zeros those bits in @var{addr}. This is only used for
+addresses of instructions, and even then not in all contexts.
+
+For example, the two low-order bits of the PC on the Hewlett-Packard PA
+2.0 architecture contain the privilege level of the corresponding
+instruction. Since instructions must always be aligned on four-byte
+boundaries, the processor masks out these bits to generate the actual
+address of the instruction. ADDR_BITS_REMOVE should filter out these
+bits with an expression such as @code{((addr) & ~3)}.
+
+@item BEFORE_MAIN_LOOP_HOOK
+Define this to expand into any code that you want to execute before the
+main loop starts. Although this is not, strictly speaking, a target
+conditional, that is how it is currently being used. Note that if a
+configuration were to define it one way for a host and a different way
+for the target, GDB will probably not compile, let alone run correctly.
+This is currently used only for the unsupported i960 Nindy target, and
+should not be used in any other configuration.
+
+@item BELIEVE_PCC_PROMOTION
+Define if the compiler promotes a short or char parameter to an int, but
+still reports the parameter as its original type, rather than the
+promoted type.
+
+@item BELIEVE_PCC_PROMOTION_TYPE
+Define this if GDB should believe the type of a short argument when
+compiled by pcc, but look within a full int space to get its value.
+Only defined for Sun-3 at present.
+
+@item BITS_BIG_ENDIAN
+Define this if the numbering of bits in the targets does *not* match the
+endianness of the target byte order. A value of 1 means that the bits
+are numbered in a big-endian order, 0 means little-endian.
+
+@item BREAKPOINT
+This is the character array initializer for the bit pattern to put into
+memory where a breakpoint is set. Although it's common to use a trap
+instruction for a breakpoint, it's not required; for instance, the bit
+pattern could be an invalid instruction. The breakpoint must be no
+longer than the shortest instruction of the architecture.
+
+@var{BREAKPOINT} has been deprecated in favour of
+@var{BREAKPOINT_FROM_PC}.
+
+@item BIG_BREAKPOINT
+@item LITTLE_BREAKPOINT
+Similar to BREAKPOINT, but used for bi-endian targets.
+
+@var{BIG_BREAKPOINT} and @var{LITTLE_BREAKPOINT} have been deprecated in
+favour of @var{BREAKPOINT_FROM_PC}.
+
+@item REMOTE_BREAKPOINT
+@item LITTLE_REMOTE_BREAKPOINT
+@item BIG_REMOTE_BREAKPOINT
+Similar to BREAKPOINT, but used for remote targets.
+
+@var{BIG_REMOTE_BREAKPOINT} and @var{LITTLE_REMOTE_BREAKPOINT} have been
+deprecated in favour of @var{BREAKPOINT_FROM_PC}.
+
+@item BREAKPOINT_FROM_PC (pcptr, lenptr)
+
+Use the program counter to determine the contents and size of a
+breakpoint instruction. It returns a pointer to a string of bytes that
+encode a breakpoint instruction, stores the length of the string to
+*lenptr, and adjusts pc (if necessary) to point to the actual memory
+location where the breakpoint should be inserted.
+
+Although it is common to use a trap instruction for a breakpoint, it's
+not required; for instance, the bit pattern could be an invalid
+instruction. The breakpoint must be no longer than the shortest
+instruction of the architecture.
+
+Replaces all the other @var{BREAKPOINT} macros.
+
+@item CALL_DUMMY_P
+A C expresson that is non-zero when the target suports inferior function
+calls.
+
+@item CALL_DUMMY_WORDS
+Pointer to an array of @var{LONGEST} words of data containing
+host-byte-ordered @var{REGISTER_BYTES} sized values that partially
+specify the sequence of instructions needed for an inferior function
+call.
+
+Should be deprecated in favour of a macro that uses target-byte-ordered
+data.
+
+@item SIZEOF_CALL_DUMMY_WORDS
+The size of @var{CALL_DUMMY_WORDS}. When @var{CALL_DUMMY_P} this must
+return a positive value. See also @var{CALL_DUMMY_LENGTH}.
+
+@item CALL_DUMMY
+A static initializer for @var{CALL_DUMMY_WORDS}. Deprecated.
+
+@item CALL_DUMMY_LOCATION
+inferior.h
+
+@item CALL_DUMMY_STACK_ADJUST
+Stack adjustment needed when performing an inferior function call.
+
+Should be deprecated in favor of something like @var{STACK_ALIGN}.
+
+@item CALL_DUMMY_STACK_ADJUST_P
+Predicate for use of @var{CALL_DUMMY_STACK_ADJUST}.
+
+Should be deprecated in favor of something like @var{STACK_ALIGN}.
+
+@item CANNOT_FETCH_REGISTER (regno)
+A C expression that should be nonzero if @var{regno} cannot be fetched
+from an inferior process. This is only relevant if
+@code{FETCH_INFERIOR_REGISTERS} is not defined.
+
+@item CANNOT_STORE_REGISTER (regno)
+A C expression that should be nonzero if @var{regno} should not be
+written to the target. This is often the case for program counters,
+status words, and other special registers. If this is not defined, GDB
+will assume that all registers may be written.
+
+@item DO_DEFERRED_STORES
+@item CLEAR_DEFERRED_STORES
+Define this to execute any deferred stores of registers into the inferior,
+and to cancel any deferred stores.
+
+Currently only implemented correctly for native Sparc configurations?
+
+@item CPLUS_MARKER
+Define this to expand into the character that G++ uses to distinguish
+compiler-generated identifiers from programmer-specified identifiers.
+By default, this expands into @code{'$'}. Most System V targets should
+define this to @code{'.'}.
+
+@item DBX_PARM_SYMBOL_CLASS
+Hook for the @code{SYMBOL_CLASS} of a parameter when decoding DBX symbol
+information. In the i960, parameters can be stored as locals or as
+args, depending on the type of the debug record.
+
+@item DECR_PC_AFTER_BREAK
+Define this to be the amount by which to decrement the PC after the
+program encounters a breakpoint. This is often the number of bytes in
+BREAKPOINT, though not always. For most targets this value will be 0.
+
+@item DECR_PC_AFTER_HW_BREAK
+Similarly, for hardware breakpoints.
+
+@item DISABLE_UNSETTABLE_BREAK addr
+If defined, this should evaluate to 1 if @var{addr} is in a shared
+library in which breakpoints cannot be set and so should be disabled.
+
+@item DO_REGISTERS_INFO
+If defined, use this to print the value of a register or all registers.
+
+@item END_OF_TEXT_DEFAULT
+This is an expression that should designate the end of the text section
+(? FIXME ?)
+
+@item EXTRACT_RETURN_VALUE(type,regbuf,valbuf)
+Define this to extract a function's return value of type @var{type} from
+the raw register state @var{regbuf} and copy that, in virtual format,
+into @var{valbuf}.
+
+@item EXTRACT_STRUCT_VALUE_ADDRESS(regbuf)
+When @var{EXTRACT_STRUCT_VALUE_ADDRESS_P} this is used to to extract
+from an array @var{regbuf} (containing the raw register state) the
+address in which a function should return its structure value, as a
+CORE_ADDR (or an expression that can be used as one).
+
+@item EXTRACT_STRUCT_VALUE_ADDRESS_P
+Predicate for @var{EXTRACT_STRUCT_VALUE_ADDRESS}.
+
+@item FLOAT_INFO
+If defined, then the `info float' command will print information about
+the processor's floating point unit.
+
+@item FP_REGNUM
+If the virtual frame pointer is kept in a register, then define this
+macro to be the number (greater than or equal to zero) of that register.
+
+This should only need to be defined if @code{TARGET_READ_FP} and
+@code{TARGET_WRITE_FP} are not defined.
+
+@item FRAMELESS_FUNCTION_INVOCATION(fi)
+Define this to an expression that returns 1 if the function invocation
+represented by @var{fi} does not have a stack frame associated with it.
+Otherwise return 0.
+
+@item FRAME_ARGS_ADDRESS_CORRECT
+stack.c
+
+@item FRAME_CHAIN(frame)
+Given @var{frame}, return a pointer to the calling frame.
+
+@item FRAME_CHAIN_COMBINE(chain,frame)
+Define this to take the frame chain pointer and the frame's nominal
+address and produce the nominal address of the caller's frame.
+Presently only defined for HP PA.
+
+@item FRAME_CHAIN_VALID(chain,thisframe)
+
+Define this to be an expression that returns zero if the given frame is
+an outermost frame, with no caller, and nonzero otherwise. Three common
+definitions are available. @code{default_frame_chain_valid} (the
+default) is nonzero if the chain pointer is nonzero and given frame's PC
+is not inside the startup file (such as @file{crt0.o}).
+@code{alternate_frame_chain_valid} is nonzero if the chain pointer is
+nonzero and the given frame's PC is not in @code{main()} or a known
+entry point function (such as @code{_start()}).
+
+@item FRAME_INIT_SAVED_REGS(frame)
+See @file{frame.h}. Determines the address of all registers in the
+current stack frame storing each in @code{frame->saved_regs}. Space for
+@code{frame->saved_regs} shall be allocated by
+@code{FRAME_INIT_SAVED_REGS} using either
+@code{frame_saved_regs_zalloc} or @code{frame_obstack_alloc}.
+
+@var{FRAME_FIND_SAVED_REGS} and @var{EXTRA_FRAME_INFO} are deprecated.
+
+@item FRAME_NUM_ARGS (fi)
+For the frame described by @var{fi} return the number of arguments that
+are being passed. If the number of arguments is not known, return
+@code{-1}.
+
+@item FRAME_SAVED_PC(frame)
+Given @var{frame}, return the pc saved there. That is, the return
+address.
+
+@item FUNCTION_EPILOGUE_SIZE
+For some COFF targets, the @code{x_sym.x_misc.x_fsize} field of the
+function end symbol is 0. For such targets, you must define
+@code{FUNCTION_EPILOGUE_SIZE} to expand into the standard size of a
+function's epilogue.
+
+@item GCC_COMPILED_FLAG_SYMBOL
+@item GCC2_COMPILED_FLAG_SYMBOL
+If defined, these are the names of the symbols that GDB will look for to
+detect that GCC compiled the file. The default symbols are
+@code{gcc_compiled.} and @code{gcc2_compiled.}, respectively. (Currently
+only defined for the Delta 68.)
+
+@item GDB_MULTI_ARCH
+If defined and non-zero, enables suport for multiple architectures
+within GDB.
+
+The support can be enabled at two levels. At level one, only
+definitions for previously undefined macros are provided; at level two,
+a multi-arch definition of all architecture dependant macros will be
+defined.
+
+@item GDB_TARGET_IS_HPPA
+This determines whether horrible kludge code in dbxread.c and
+partial-stab.h is used to mangle multiple-symbol-table files from
+HPPA's. This should all be ripped out, and a scheme like elfread.c
+used.
+
+@item GET_LONGJMP_TARGET
+For most machines, this is a target-dependent parameter. On the
+DECstation and the Iris, this is a native-dependent parameter, since
+<setjmp.h> is needed to define it.
+
+This macro determines the target PC address that longjmp() will jump to,
+assuming that we have just stopped at a longjmp breakpoint. It takes a
+CORE_ADDR * as argument, and stores the target PC value through this
+pointer. It examines the current state of the machine as needed.
+
+@item GET_SAVED_REGISTER
+Define this if you need to supply your own definition for the function
+@code{get_saved_register}.
+
+@item HAVE_REGISTER_WINDOWS
+Define this if the target has register windows.
+@item REGISTER_IN_WINDOW_P (regnum)
+Define this to be an expression that is 1 if the given register is in
+the window.
+
+@item IBM6000_TARGET
+Shows that we are configured for an IBM RS/6000 target. This
+conditional should be eliminated (FIXME) and replaced by
+feature-specific macros. It was introduced in haste and we are
+repenting at leisure.
+
+@item IEEE_FLOAT
+Define this if the target system uses IEEE-format floating point numbers.
+
+@item INIT_EXTRA_FRAME_INFO (fromleaf, frame)
+If additional information about the frame is required this should be
+stored in @code{frame->extra_info}. Space for @code{frame->extra_info}
+is allocated using @code{frame_obstack_alloc}.
+
+@item INIT_FRAME_PC (fromleaf, prev)
+This is a C statement that sets the pc of the frame pointed to by
+@var{prev}. [By default...]
+
+@item INNER_THAN (lhs,rhs)
+Returns non-zero if stack address @var{lhs} is inner than (nearer to the
+stack top) stack address @var{rhs}. Define this as @code{lhs < rhs} if
+the target's stack grows downward in memory, or @code{lhs > rsh} if the
+stack grows upward.
+
+@item IN_SIGTRAMP (pc, name)
+Define this to return true if the given @var{pc} and/or @var{name}
+indicates that the current function is a sigtramp.
+
+@item SIGTRAMP_START (pc)
+@item SIGTRAMP_END (pc)
+Define these to be the start and end address of the sigtramp for the
+given @var{pc}. On machines where the address is just a compile time
+constant, the macro expansion will typically just ignore the supplied
+@var{pc}.
+
+@item IN_SOLIB_CALL_TRAMPOLINE pc name
+Define this to evaluate to nonzero if the program is stopped in the
+trampoline that connects to a shared library.
+
+@item IN_SOLIB_RETURN_TRAMPOLINE pc name
+Define this to evaluate to nonzero if the program is stopped in the
+trampoline that returns from a shared library.
+
+@item IN_SOLIB_DYNSYM_RESOLVE_CODE pc
+Define this to evaluate to nonzero if the program is stopped in the
+dynamic linker.
+
+@item SKIP_SOLIB_RESOLVER pc
+Define this to evaluate to the (nonzero) address at which execution
+should continue to get past the dynamic linker's symbol resolution
+function. A zero value indicates that it is not important or necessary
+to set a breakpoint to get through the dynamic linker and that single
+stepping will suffice.
+
+@item IS_TRAPPED_INTERNALVAR (name)
+This is an ugly hook to allow the specification of special actions that
+should occur as a side-effect of setting the value of a variable
+internal to GDB. Currently only used by the h8500. Note that this
+could be either a host or target conditional.
+
+@item NEED_TEXT_START_END
+Define this if GDB should determine the start and end addresses of the
+text section. (Seems dubious.)
+
+@item NO_HIF_SUPPORT
+(Specific to the a29k.)
+
+@item SOFTWARE_SINGLE_STEP_P
+Define this as 1 if the target does not have a hardware single-step
+mechanism. The macro @code{SOFTWARE_SINGLE_STEP} must also be defined.
+
+@item SOFTWARE_SINGLE_STEP(signal,insert_breapoints_p)
+A function that inserts or removes (dependant on
+@var{insert_breapoints_p}) breakpoints at each possible destinations of
+the next instruction. See @code{sparc-tdep.c} and @code{rs6000-tdep.c}
+for examples.
+
+@item PCC_SOL_BROKEN
+(Used only in the Convex target.)
+
+@item PC_IN_CALL_DUMMY
+inferior.h
+
+@item PC_LOAD_SEGMENT
+If defined, print information about the load segment for the program
+counter. (Defined only for the RS/6000.)
+
+@item PC_REGNUM
+If the program counter is kept in a register, then define this macro to
+be the number (greater than or equal to zero) of that register.
+
+This should only need to be defined if @code{TARGET_READ_PC} and
+@code{TARGET_WRITE_PC} are not defined.
+
+@item NPC_REGNUM
+The number of the ``next program counter'' register, if defined.
+
+@item NNPC_REGNUM
+The number of the ``next next program counter'' register, if defined.
+Currently, this is only defined for the Motorola 88K.
+
+@item PRINT_REGISTER_HOOK (regno)
+If defined, this must be a function that prints the contents of the
+given register to standard output.
+
+@item PRINT_TYPELESS_INTEGER
+This is an obscure substitute for @code{print_longest} that seems to
+have been defined for the Convex target.
+
+@item PROCESS_LINENUMBER_HOOK
+A hook defined for XCOFF reading.
+
+@item PROLOGUE_FIRSTLINE_OVERLAP
+(Only used in unsupported Convex configuration.)
+
+@item PS_REGNUM
+If defined, this is the number of the processor status register. (This
+definition is only used in generic code when parsing "$ps".)
+
+@item POP_FRAME
+Used in @samp{call_function_by_hand} to remove an artificial stack
+frame.
+
+@item PUSH_ARGUMENTS (nargs, args, sp, struct_return, struct_addr)
+Define this to push arguments onto the stack for inferior function
+call. Return the updated stack pointer value.
+
+@item PUSH_DUMMY_FRAME
+Used in @samp{call_function_by_hand} to create an artificial stack frame.
+
+@item REGISTER_BYTES
+The total amount of space needed to store GDB's copy of the machine's
+register state.
+
+@item REGISTER_NAME(i)
+Return the name of register @var{i} as a string. May return @var{NULL}
+or @var{NUL} to indicate that register @var{i} is not valid.
+
+@item REGISTER_NAMES
+Deprecated in favor of @var{REGISTER_NAME}.
+
+@item REG_STRUCT_HAS_ADDR (gcc_p, type)
+Define this to return 1 if the given type will be passed by pointer
+rather than directly.
+
+@item SAVE_DUMMY_FRAME_TOS (sp)
+Used in @samp{call_function_by_hand} to notify the target dependent code
+of the top-of-stack value that will be passed to the the inferior code.
+This is the value of the @var{SP} after both the dummy frame and space
+for parameters/results have been allocated on the stack.
+
+@item SDB_REG_TO_REGNUM
+Define this to convert sdb register numbers into GDB regnums. If not
+defined, no conversion will be done.
+
+@item SHIFT_INST_REGS
+(Only used for m88k targets.)
+
+@item SKIP_PROLOGUE (pc)
+A C expression that returns the address of the ``real'' code beyond the
+function entry prologue found at @var{pc}.
+
+@item SKIP_PROLOGUE_FRAMELESS_P
+A C expression that should behave similarly, but that can stop as soon
+as the function is known to have a frame. If not defined,
+@code{SKIP_PROLOGUE} will be used instead.
+
+@item SKIP_TRAMPOLINE_CODE (pc)
+If the target machine has trampoline code that sits between callers and
+the functions being called, then define this macro to return a new PC
+that is at the start of the real function.
+
+@item SP_REGNUM
+If the stack-pointer is kept in a register, then define this macro to be
+the number (greater than or equal to zero) of that register.
+
+This should only need to be defined if @code{TARGET_WRITE_SP} and
+@code{TARGET_WRITE_SP} are not defined.
+
+@item STAB_REG_TO_REGNUM
+Define this to convert stab register numbers (as gotten from `r'
+declarations) into GDB regnums. If not defined, no conversion will be
+done.
+
+@item STACK_ALIGN (addr)
+Define this to adjust the address to the alignment required for the
+processor's stack.
+
+@item STEP_SKIPS_DELAY (addr)
+Define this to return true if the address is of an instruction with a
+delay slot. If a breakpoint has been placed in the instruction's delay
+slot, GDB will single-step over that instruction before resuming
+normally. Currently only defined for the Mips.
+
+@item STORE_RETURN_VALUE (type, valbuf)
+A C expression that stores a function return value of type @var{type},
+where @var{valbuf} is the address of the value to be stored.
+
+@item SUN_FIXED_LBRAC_BUG
+(Used only for Sun-3 and Sun-4 targets.)
+
+@item SYMBOL_RELOADING_DEFAULT
+The default value of the `symbol-reloading' variable. (Never defined in
+current sources.)
+
+@item TARGET_BYTE_ORDER_DEFAULT
+The ordering of bytes in the target. This must be either
+@code{BIG_ENDIAN} or @code{LITTLE_ENDIAN}. This macro replaces
+@var{TARGET_BYTE_ORDER} which is deprecated.
+
+@item TARGET_BYTE_ORDER_SELECTABLE_P
+Non-zero if the target has both @code{BIG_ENDIAN} and
+@code{LITTLE_ENDIAN} variants. This macro replaces
+@var{TARGET_BYTE_ORDER_SELECTABLE} which is deprecated.
+
+@item TARGET_CHAR_BIT
+Number of bits in a char; defaults to 8.
+
+@item TARGET_COMPLEX_BIT
+Number of bits in a complex number; defaults to @code{2 * TARGET_FLOAT_BIT}.
+
+At present this macro is not used.
+
+@item TARGET_DOUBLE_BIT
+Number of bits in a double float; defaults to @code{8 * TARGET_CHAR_BIT}.
+
+@item TARGET_DOUBLE_COMPLEX_BIT
+Number of bits in a double complex; defaults to @code{2 * TARGET_DOUBLE_BIT}.
+
+At present this macro is not used.
+
+@item TARGET_FLOAT_BIT
+Number of bits in a float; defaults to @code{4 * TARGET_CHAR_BIT}.
+
+@item TARGET_INT_BIT
+Number of bits in an integer; defaults to @code{4 * TARGET_CHAR_BIT}.
+
+@item TARGET_LONG_BIT
+Number of bits in a long integer; defaults to @code{4 * TARGET_CHAR_BIT}.
+
+@item TARGET_LONG_DOUBLE_BIT
+Number of bits in a long double float;
+defaults to @code{2 * TARGET_DOUBLE_BIT}.
+
+@item TARGET_LONG_LONG_BIT
+Number of bits in a long long integer; defaults to @code{2 * TARGET_LONG_BIT}.
+
+@item TARGET_PTR_BIT
+Number of bits in a pointer; defaults to @code{TARGET_INT_BIT}.
+
+@item TARGET_SHORT_BIT
+Number of bits in a short integer; defaults to @code{2 * TARGET_CHAR_BIT}.
+
+@item TARGET_READ_PC
+@item TARGET_WRITE_PC (val, pid)
+@item TARGET_READ_SP
+@item TARGET_WRITE_SP
+@item TARGET_READ_FP
+@item TARGET_WRITE_FP
+These change the behavior of @code{read_pc}, @code{write_pc},
+@code{read_sp}, @code{write_sp}, @code{read_fp} and @code{write_fp}.
+For most targets, these may be left undefined. GDB will call the read
+and write register functions with the relevant @code{_REGNUM} argument.
+
+These macros are useful when a target keeps one of these registers in a
+hard to get at place; for example, part in a segment register and part
+in an ordinary register.
+
+@item TARGET_VIRTUAL_FRAME_POINTER(pc,regp,offsetp)
+Returns a @code{(register, offset)} pair representing the virtual
+frame pointer in use at the code address @code{"pc"}. If virtual
+frame pointers are not used, a default definition simply returns
+@code{FP_REGNUM}, with an offset of zero.
+
+@item USE_STRUCT_CONVENTION (gcc_p, type)
+If defined, this must be an expression that is nonzero if a value of the
+given @var{type} being returned from a function must have space
+allocated for it on the stack. @var{gcc_p} is true if the function
+being considered is known to have been compiled by GCC; this is helpful
+for systems where GCC is known to use different calling convention than
+other compilers.
+
+@item VARIABLES_INSIDE_BLOCK (desc, gcc_p)
+For dbx-style debugging information, if the compiler puts variable
+declarations inside LBRAC/RBRAC blocks, this should be defined to be
+nonzero. @var{desc} is the value of @code{n_desc} from the
+@code{N_RBRAC} symbol, and @var{gcc_p} is true if GDB has noticed the
+presence of either the @code{GCC_COMPILED_SYMBOL} or the
+@code{GCC2_COMPILED_SYMBOL}. By default, this is 0.
+
+@item OS9K_VARIABLES_INSIDE_BLOCK (desc, gcc_p)
+Similarly, for OS/9000. Defaults to 1.
+
+@end table
+
+Motorola M68K target conditionals.
+
+@table @code
+
+@item BPT_VECTOR
+Define this to be the 4-bit location of the breakpoint trap vector. If
+not defined, it will default to @code{0xf}.
+
+@item REMOTE_BPT_VECTOR
+Defaults to @code{1}.
+
+@end table
+
+@section Adding a New Target
+
+The following files define a target to GDB:
+
+@table @file
+
+@item gdb/config/@var{arch}/@var{ttt}.mt
+Contains a Makefile fragment specific to this target. Specifies what
+object files are needed for target @var{ttt}, by defining
+@samp{TDEPFILES=@dots{}} and @samp{TDEPLIBS=@dots{}}. Also specifies
+the header file which describes @var{ttt}, by defining @samp{TM_FILE=
+tm-@var{ttt}.h}.
+
+You can also define @samp{TM_CFLAGS}, @samp{TM_CLIBS}, @samp{TM_CDEPS},
+but these are now deprecated, replaced by autoconf, and may go away in
+future versions of GDB.
+
+@item gdb/config/@var{arch}/tm-@var{ttt}.h
+(@file{tm.h} is a link to this file, created by configure). Contains
+macro definitions about the target machine's registers, stack frame
+format and instructions.
+
+@item gdb/@var{ttt}-tdep.c
+Contains any miscellaneous code required for this target machine. On
+some machines it doesn't exist at all. Sometimes the macros in
+@file{tm-@var{ttt}.h} become very complicated, so they are implemented
+as functions here instead, and the macro is simply defined to call the
+function. This is vastly preferable, since it is easier to understand
+and debug.
+
+@item gdb/config/@var{arch}/tm-@var{arch}.h
+This often exists to describe the basic layout of the target machine's
+processor chip (registers, stack, etc). If used, it is included by
+@file{tm-@var{ttt}.h}. It can be shared among many targets that use the
+same processor.
+
+@item gdb/@var{arch}-tdep.c
+Similarly, there are often common subroutines that are shared by all
+target machines that use this particular architecture.
+
+@end table
+
+If you are adding a new operating system for an existing CPU chip, add a
+@file{config/tm-@var{os}.h} file that describes the operating system
+facilities that are unusual (extra symbol table info; the breakpoint
+instruction needed; etc). Then write a @file{@var{arch}/tm-@var{os}.h}
+that just @code{#include}s @file{tm-@var{arch}.h} and
+@file{config/tm-@var{os}.h}.
+
+
+@node Target Vector Definition
+
+@chapter Target Vector Definition
+
+The target vector defines the interface between GDB's abstract handling
+of target systems, and the nitty-gritty code that actually exercises
+control over a process or a serial port. GDB includes some 30-40
+different target vectors; however, each configuration of GDB includes
+only a few of them.
+
+@section File Targets
+
+Both executables and core files have target vectors.
+
+@section Standard Protocol and Remote Stubs
+
+GDB's file @file{remote.c} talks a serial protocol to code that runs in
+the target system. GDB provides several sample ``stubs'' that can be
+integrated into target programs or operating systems for this purpose;
+they are named @file{*-stub.c}.
+
+The GDB user's manual describes how to put such a stub into your target
+code. What follows is a discussion of integrating the SPARC stub into a
+complicated operating system (rather than a simple program), by Stu
+Grossman, the author of this stub.
+
+The trap handling code in the stub assumes the following upon entry to
+trap_low:
+
+@enumerate
+
+@item %l1 and %l2 contain pc and npc respectively at the time of the trap
+
+@item traps are disabled
+
+@item you are in the correct trap window
+
+@end enumerate
+
+As long as your trap handler can guarantee those conditions, then there
+is no reason why you shouldn't be able to `share' traps with the stub.
+The stub has no requirement that it be jumped to directly from the
+hardware trap vector. That is why it calls @code{exceptionHandler()},
+which is provided by the external environment. For instance, this could
+setup the hardware traps to actually execute code which calls the stub
+first, and then transfers to its own trap handler.
+
+For the most point, there probably won't be much of an issue with
+`sharing' traps, as the traps we use are usually not used by the kernel,
+and often indicate unrecoverable error conditions. Anyway, this is all
+controlled by a table, and is trivial to modify. The most important
+trap for us is for @code{ta 1}. Without that, we can't single step or
+do breakpoints. Everything else is unnecessary for the proper operation
+of the debugger/stub.
+
+From reading the stub, it's probably not obvious how breakpoints work.
+They are simply done by deposit/examine operations from GDB.
+
+@section ROM Monitor Interface
+
+@section Custom Protocols
+
+@section Transport Layer
+
+@section Builtin Simulator
+
+
+@node Native Debugging
+
+@chapter Native Debugging
+
+Several files control GDB's configuration for native support:
+
+@table @file
+
+@item gdb/config/@var{arch}/@var{xyz}.mh
+Specifies Makefile fragments needed when hosting @emph{or native} on
+machine @var{xyz}. In particular, this lists the required
+native-dependent object files, by defining @samp{NATDEPFILES=@dots{}}.
+Also specifies the header file which describes native support on
+@var{xyz}, by defining @samp{NAT_FILE= nm-@var{xyz}.h}. You can also
+define @samp{NAT_CFLAGS}, @samp{NAT_ADD_FILES}, @samp{NAT_CLIBS},
+@samp{NAT_CDEPS}, etc.; see @file{Makefile.in}.
+
+@item gdb/config/@var{arch}/nm-@var{xyz}.h
+(@file{nm.h} is a link to this file, created by configure). Contains C
+macro definitions describing the native system environment, such as
+child process control and core file support.
+
+@item gdb/@var{xyz}-nat.c
+Contains any miscellaneous C code required for this native support of
+this machine. On some machines it doesn't exist at all.
+
+@end table
+
+There are some ``generic'' versions of routines that can be used by
+various systems. These can be customized in various ways by macros
+defined in your @file{nm-@var{xyz}.h} file. If these routines work for
+the @var{xyz} host, you can just include the generic file's name (with
+@samp{.o}, not @samp{.c}) in @code{NATDEPFILES}.
+
+Otherwise, if your machine needs custom support routines, you will need
+to write routines that perform the same functions as the generic file.
+Put them into @code{@var{xyz}-nat.c}, and put @code{@var{xyz}-nat.o}
+into @code{NATDEPFILES}.
+
+@table @file
+
+@item inftarg.c
+This contains the @emph{target_ops vector} that supports Unix child
+processes on systems which use ptrace and wait to control the child.
+
+@item procfs.c
+This contains the @emph{target_ops vector} that supports Unix child
+processes on systems which use /proc to control the child.
+
+@item fork-child.c
+This does the low-level grunge that uses Unix system calls to do a "fork
+and exec" to start up a child process.
+
+@item infptrace.c
+This is the low level interface to inferior processes for systems using
+the Unix @code{ptrace} call in a vanilla way.
+
+@end table
+
+@section Native core file Support
+
+@table @file
+
+@item core-aout.c::fetch_core_registers()
+Support for reading registers out of a core file. This routine calls
+@code{register_addr()}, see below. Now that BFD is used to read core
+files, virtually all machines should use @code{core-aout.c}, and should
+just provide @code{fetch_core_registers} in @code{@var{xyz}-nat.c} (or
+@code{REGISTER_U_ADDR} in @code{nm-@var{xyz}.h}).
+
+@item core-aout.c::register_addr()
+If your @code{nm-@var{xyz}.h} file defines the macro
+@code{REGISTER_U_ADDR(addr, blockend, regno)}, it should be defined to
+set @code{addr} to the offset within the @samp{user} struct of GDB
+register number @code{regno}. @code{blockend} is the offset within the
+``upage'' of @code{u.u_ar0}. If @code{REGISTER_U_ADDR} is defined,
+@file{core-aout.c} will define the @code{register_addr()} function and
+use the macro in it. If you do not define @code{REGISTER_U_ADDR}, but
+you are using the standard @code{fetch_core_registers()}, you will need
+to define your own version of @code{register_addr()}, put it into your
+@code{@var{xyz}-nat.c} file, and be sure @code{@var{xyz}-nat.o} is in
+the @code{NATDEPFILES} list. If you have your own
+@code{fetch_core_registers()}, you may not need a separate
+@code{register_addr()}. Many custom @code{fetch_core_registers()}
+implementations simply locate the registers themselves.@refill
+
+@end table
+
+When making GDB run native on a new operating system, to make it
+possible to debug core files, you will need to either write specific
+code for parsing your OS's core files, or customize
+@file{bfd/trad-core.c}. First, use whatever @code{#include} files your
+machine uses to define the struct of registers that is accessible
+(possibly in the u-area) in a core file (rather than
+@file{machine/reg.h}), and an include file that defines whatever header
+exists on a core file (e.g. the u-area or a @samp{struct core}). Then
+modify @code{trad_unix_core_file_p()} to use these values to set up the
+section information for the data segment, stack segment, any other
+segments in the core file (perhaps shared library contents or control
+information), ``registers'' segment, and if there are two discontiguous
+sets of registers (e.g. integer and float), the ``reg2'' segment. This
+section information basically delimits areas in the core file in a
+standard way, which the section-reading routines in BFD know how to seek
+around in.
+
+Then back in GDB, you need a matching routine called
+@code{fetch_core_registers()}. If you can use the generic one, it's in
+@file{core-aout.c}; if not, it's in your @file{@var{xyz}-nat.c} file.
+It will be passed a char pointer to the entire ``registers'' segment,
+its length, and a zero; or a char pointer to the entire ``regs2''
+segment, its length, and a 2. The routine should suck out the supplied
+register values and install them into GDB's ``registers'' array.
+
+If your system uses @file{/proc} to control processes, and uses ELF
+format core files, then you may be able to use the same routines for
+reading the registers out of processes and out of core files.
+
+@section ptrace
+
+@section /proc
+
+@section win32
+
+@section shared libraries
+
+@section Native Conditionals
+
+When GDB is configured and compiled, various macros are defined or left
+undefined, to control compilation when the host and target systems are
+the same. These macros should be defined (or left undefined) in
+@file{nm-@var{system}.h}.
+
+@table @code
+
+@item ATTACH_DETACH
+If defined, then GDB will include support for the @code{attach} and
+@code{detach} commands.
+
+@item CHILD_PREPARE_TO_STORE
+If the machine stores all registers at once in the child process, then
+define this to ensure that all values are correct. This usually entails
+a read from the child.
+
+[Note that this is incorrectly defined in @file{xm-@var{system}.h} files
+currently.]
+
+@item FETCH_INFERIOR_REGISTERS
+Define this if the native-dependent code will provide its own routines
+@code{fetch_inferior_registers} and @code{store_inferior_registers} in
+@file{@var{HOST}-nat.c}. If this symbol is @emph{not} defined, and
+@file{infptrace.c} is included in this configuration, the default
+routines in @file{infptrace.c} are used for these functions.
+
+@item FILES_INFO_HOOK
+(Only defined for Convex.)
+
+@item FP0_REGNUM
+This macro is normally defined to be the number of the first floating
+point register, if the machine has such registers. As such, it would
+appear only in target-specific code. However, /proc support uses this
+to decide whether floats are in use on this target.
+
+@item GET_LONGJMP_TARGET
+For most machines, this is a target-dependent parameter. On the
+DECstation and the Iris, this is a native-dependent parameter, since
+<setjmp.h> is needed to define it.
+
+This macro determines the target PC address that longjmp() will jump to,
+assuming that we have just stopped at a longjmp breakpoint. It takes a
+CORE_ADDR * as argument, and stores the target PC value through this
+pointer. It examines the current state of the machine as needed.
+
+@item KERNEL_U_ADDR
+Define this to the address of the @code{u} structure (the ``user
+struct'', also known as the ``u-page'') in kernel virtual memory. GDB
+needs to know this so that it can subtract this address from absolute
+addresses in the upage, that are obtained via ptrace or from core files.
+On systems that don't need this value, set it to zero.
+
+@item KERNEL_U_ADDR_BSD
+Define this to cause GDB to determine the address of @code{u} at
+runtime, by using Berkeley-style @code{nlist} on the kernel's image in
+the root directory.
+
+@item KERNEL_U_ADDR_HPUX
+Define this to cause GDB to determine the address of @code{u} at
+runtime, by using HP-style @code{nlist} on the kernel's image in the
+root directory.
+
+@item ONE_PROCESS_WRITETEXT
+Define this to be able to, when a breakpoint insertion fails, warn the
+user that another process may be running with the same executable.
+
+@item PREPARE_TO_PROCEED @var{select_it}
+This (ugly) macro allows a native configuration to customize the way the
+@code{proceed} function in @file{infrun.c} deals with switching between
+threads.
+
+In a multi-threaded task we may select another thread and then continue
+or step. But if the old thread was stopped at a breakpoint, it will
+immediately cause another breakpoint stop without any execution (i.e. it
+will report a breakpoint hit incorrectly). So GDB must step over it
+first.
+
+If defined, @code{PREPARE_TO_PROCEED} should check the current thread
+against the thread that reported the most recent event. If a step-over
+is required, it returns TRUE. If @var{select_it} is non-zero, it should
+reselect the old thread.
+
+@item PROC_NAME_FMT
+Defines the format for the name of a @file{/proc} device. Should be
+defined in @file{nm.h} @emph{only} in order to override the default
+definition in @file{procfs.c}.
+
+@item PTRACE_FP_BUG
+mach386-xdep.c
+
+@item PTRACE_ARG3_TYPE
+The type of the third argument to the @code{ptrace} system call, if it
+exists and is different from @code{int}.
+
+@item REGISTER_U_ADDR
+Defines the offset of the registers in the ``u area''.
+
+@item SHELL_COMMAND_CONCAT
+If defined, is a string to prefix on the shell command used to start the
+inferior.
+
+@item SHELL_FILE
+If defined, this is the name of the shell to use to run the inferior.
+Defaults to @code{"/bin/sh"}.
+
+@item SOLIB_ADD (filename, from_tty, targ)
+Define this to expand into an expression that will cause the symbols in
+@var{filename} to be added to GDB's symbol table.
+
+@item SOLIB_CREATE_INFERIOR_HOOK
+Define this to expand into any shared-library-relocation code that you
+want to be run just after the child process has been forked.
+
+@item START_INFERIOR_TRAPS_EXPECTED
+When starting an inferior, GDB normally expects to trap twice; once when
+the shell execs, and once when the program itself execs. If the actual
+number of traps is something other than 2, then define this macro to
+expand into the number expected.
+
+@item SVR4_SHARED_LIBS
+Define this to indicate that SVR4-style shared libraries are in use.
+
+@item USE_PROC_FS
+This determines whether small routines in @file{*-tdep.c}, which
+translate register values between GDB's internal representation and the
+/proc representation, are compiled.
+
+@item U_REGS_OFFSET
+This is the offset of the registers in the upage. It need only be
+defined if the generic ptrace register access routines in
+@file{infptrace.c} are being used (that is, @file{infptrace.c} is
+configured in, and @code{FETCH_INFERIOR_REGISTERS} is not defined). If
+the default value from @file{infptrace.c} is good enough, leave it
+undefined.
+
+The default value means that u.u_ar0 @emph{points to} the location of
+the registers. I'm guessing that @code{#define U_REGS_OFFSET 0} means
+that u.u_ar0 @emph{is} the location of the registers.
+
+@item CLEAR_SOLIB
+objfiles.c
+
+@item DEBUG_PTRACE
+Define this to debug ptrace calls.
+
+@end table
+
+
+@node Support Libraries
+
+@chapter Support Libraries
+
+@section BFD
+
+BFD provides support for GDB in several ways:
+
+@table @emph
+
+@item identifying executable and core files
+BFD will identify a variety of file types, including a.out, coff, and
+several variants thereof, as well as several kinds of core files.
+
+@item access to sections of files
+BFD parses the file headers to determine the names, virtual addresses,
+sizes, and file locations of all the various named sections in files
+(such as the text section or the data section). GDB simply calls BFD to
+read or write section X at byte offset Y for length Z.
+
+@item specialized core file support
+BFD provides routines to determine the failing command name stored in a
+core file, the signal with which the program failed, and whether a core
+file matches (i.e. could be a core dump of) a particular executable
+file.
+
+@item locating the symbol information
+GDB uses an internal interface of BFD to determine where to find the
+symbol information in an executable file or symbol-file. GDB itself
+handles the reading of symbols, since BFD does not ``understand'' debug
+symbols, but GDB uses BFD's cached information to find the symbols,
+string table, etc.
+
+@end table
+
+@section opcodes
+
+The opcodes library provides GDB's disassembler. (It's a separate
+library because it's also used in binutils, for @file{objdump}).
+
+@section readline
+
+@section mmalloc
+
+@section libiberty
+
+@section gnu-regex
+
+Regex conditionals.
+
+@table @code
+
+@item C_ALLOCA
+
+@item NFAILURES
+
+@item RE_NREGS
+
+@item SIGN_EXTEND_CHAR
+
+@item SWITCH_ENUM_BUG
+
+@item SYNTAX_TABLE
+
+@item Sword
+
+@item sparc
+
+@end table
+
+@section include
+
+@node Coding
+
+@chapter Coding
+
+This chapter covers topics that are lower-level than the major
+algorithms of GDB.
+
+@section Cleanups
Cleanups are a structured way to deal with things that need to be done
-later. When your code does something (like malloc some memory, or open
-a file) that needs to be undone later (e.g. free the memory or close
-the file), it can make a cleanup. The cleanup will be done at some
-future point: when the command is finished, when an error occurs, or
-when your code decides it's time to do cleanups.
+later. When your code does something (like @code{malloc} some memory,
+or open a file) that needs to be undone later (e.g. free the memory or
+close the file), it can make a cleanup. The cleanup will be done at
+some future point: when the command is finished, when an error occurs,
+or when your code decides it's time to do cleanups.
You can also discard cleanups, that is, throw them away without doing
what they say. This is only done if you ask that it be done.
Syntax:
- old_chain = make_cleanup (function, arg);
+@table @code
+
+@item struct cleanup *@var{old_chain};
+Declare a variable which will hold a cleanup chain handle.
+
+@item @var{old_chain} = make_cleanup (@var{function}, @var{arg});
+Make a cleanup which will cause @var{function} to be called with
+@var{arg} (a @code{char *}) later. The result, @var{old_chain}, is a
+handle that can be passed to @code{do_cleanups} or
+@code{discard_cleanups} later. Unless you are going to call
+@code{do_cleanups} or @code{discard_cleanups} yourself, you can ignore
+the result from @code{make_cleanup}.
+
+@item do_cleanups (@var{old_chain});
+Perform all cleanups done since @code{make_cleanup} returned
+@var{old_chain}. E.g.:
+@example
+make_cleanup (a, 0);
+old = make_cleanup (b, 0);
+do_cleanups (old);
+@end example
+@noindent
+will call @code{b()} but will not call @code{a()}. The cleanup that
+calls @code{a()} will remain in the cleanup chain, and will be done
+later unless otherwise discarded.@refill
+
+@item discard_cleanups (@var{old_chain});
+Same as @code{do_cleanups} except that it just removes the cleanups from
+the chain and does not call the specified functions.
+
+@end table
+
+Some functions, e.g. @code{fputs_filtered()} or @code{error()}, specify
+that they ``should not be called when cleanups are not in place''. This
+means that any actions you need to reverse in the case of an error or
+interruption must be on the cleanup chain before you call these
+functions, since they might never return to your code (they
+@samp{longjmp} instead).
+
+@section Wrapping Output Lines
+
+Output that goes through @code{printf_filtered} or @code{fputs_filtered}
+or @code{fputs_demangled} needs only to have calls to @code{wrap_here}
+added in places that would be good breaking points. The utility
+routines will take care of actually wrapping if the line width is
+exceeded.
+
+The argument to @code{wrap_here} is an indentation string which is
+printed @emph{only} if the line breaks there. This argument is saved
+away and used later. It must remain valid until the next call to
+@code{wrap_here} or until a newline has been printed through the
+@code{*_filtered} functions. Don't pass in a local variable and then
+return!
+
+It is usually best to call @code{wrap_here()} after printing a comma or
+space. If you call it before printing a space, make sure that your
+indentation properly accounts for the leading space that will print if
+the line wraps there.
+
+Any function or set of functions that produce filtered output must
+finish by printing a newline, to flush the wrap buffer, before switching
+to unfiltered (``@code{printf}'') output. Symbol reading routines that
+print warnings are a good example.
+
+@section GDB Coding Standards
+
+GDB follows the GNU coding standards, as described in
+@file{etc/standards.texi}. This file is also available for anonymous
+FTP from GNU archive sites. GDB takes a strict interpretation of the
+standard; in general, when the GNU standard recommends a practice but
+does not require it, GDB requires it.
+
+GDB follows an additional set of coding standards specific to GDB,
+as described in the following sections.
+
+You can configure with @samp{--enable-build-warnings} to get GCC to
+check on a number of these rules. GDB sources ought not to engender any
+complaints, unless they are caused by bogus host systems. (The exact
+set of enabled warnings is currently @samp{-Wall -Wpointer-arith
+-Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations}.
+
+@subsection Formatting
+
+The standard GNU recommendations for formatting must be followed
+strictly.
+
+Note that while in a definition, the function's name must be in column
+zero; in a function declaration, the name must be on the same line as
+the return type.
+
+In addition, there must be a space between a function or macro name and
+the opening parenthesis of its argument list (except for macro
+definitions, as required by C). There must not be a space after an open
+paren/bracket or before a close paren/bracket.
+
+While additional whitespace is generally helpful for reading, do not use
+more than one blank line to separate blocks, and avoid adding whitespace
+after the end of a program line (as of 1/99, some 600 lines had whitespace
+after the semicolon). Excess whitespace causes difficulties for diff and
+patch.
+
+@subsection Comments
+
+The standard GNU requirements on comments must be followed strictly.
+
+Block comments must appear in the following form, with no `/*'- or
+'*/'-only lines, and no leading `*':
+
+@example @code
+/* Wait for control to return from inferior to debugger. If inferior
+ gets a signal, we may decide to start it up again instead of
+ returning. That is why there is a loop in this function. When
+ this function actually returns it means the inferior should be left
+ stopped and GDB should read more commands. */
+@end example
+
+(Note that this format is encouraged by Emacs; tabbing for a multi-line
+comment works correctly, and M-Q fills the block consistently.)
+
+Put a blank line between the block comments preceding function or
+variable definitions, and the definition itself.
+
+In general, put function-body comments on lines by themselves, rather
+than trying to fit them into the 20 characters left at the end of a
+line, since either the comment or the code will inevitably get longer
+than will fit, and then somebody will have to move it anyhow.
+
+@subsection C Usage
+
+Code must not depend on the sizes of C data types, the format of the
+host's floating point numbers, the alignment of anything, or the order
+of evaluation of expressions.
+
+Use functions freely. There are only a handful of compute-bound areas
+in GDB that might be affected by the overhead of a function call, mainly
+in symbol reading. Most of GDB's performance is limited by the target
+interface (whether serial line or system call).
+
+However, use functions with moderation. A thousand one-line functions
+are just as hard to understand as a single thousand-line function.
+
+@subsection Function Prototypes
+
+Prototypes must be used to @emph{declare} functions, and may be used to
+@emph{define} them. Prototypes for GDB functions must include both the
+argument type and name, with the name matching that used in the actual
+function definition.
+
+All external functions should have a declaration in a header file that
+callers include, except for @code{_initialize_*} functions, which must
+be external so that @file{init.c} construction works, but shouldn't be
+visible to random source files.
+
+All static functions must be declared in a block near the top of the
+source file.
+
+@subsection Clean Design
+
+In addition to getting the syntax right, there's the little question of
+semantics. Some things are done in certain ways in GDB because long
+experience has shown that the more obvious ways caused various kinds of
+trouble.
+
+You can't assume the byte order of anything that comes from a target
+(including @var{value}s, object files, and instructions). Such things
+must be byte-swapped using @code{SWAP_TARGET_AND_HOST} in GDB, or one of
+the swap routines defined in @file{bfd.h}, such as @code{bfd_get_32}.
+
+You can't assume that you know what interface is being used to talk to
+the target system. All references to the target must go through the
+current @code{target_ops} vector.
+
+You can't assume that the host and target machines are the same machine
+(except in the ``native'' support modules). In particular, you can't
+assume that the target machine's header files will be available on the
+host machine. Target code must bring along its own header files --
+written from scratch or explicitly donated by their owner, to avoid
+copyright problems.
+
+Insertion of new @code{#ifdef}'s will be frowned upon. It's much better
+to write the code portably than to conditionalize it for various
+systems.
+
+New @code{#ifdef}'s which test for specific compilers or manufacturers
+or operating systems are unacceptable. All @code{#ifdef}'s should test
+for features. The information about which configurations contain which
+features should be segregated into the configuration files. Experience
+has proven far too often that a feature unique to one particular system
+often creeps into other systems; and that a conditional based on some
+predefined macro for your current system will become worthless over
+time, as new versions of your system come out that behave differently
+with regard to this feature.
+
+Adding code that handles specific architectures, operating systems,
+target interfaces, or hosts, is not acceptable in generic code. If a
+hook is needed at that point, invent a generic hook and define it for
+your configuration, with something like:
+
+@example
+#ifdef WRANGLE_SIGNALS
+ WRANGLE_SIGNALS (signo);
+#endif
+@end example
+
+In your host, target, or native configuration file, as appropriate,
+define @code{WRANGLE_SIGNALS} to do the machine-dependent thing. Take a
+bit of care in defining the hook, so that it can be used by other ports
+in the future, if they need a hook in the same place.
+
+If the hook is not defined, the code should do whatever "most" machines
+want. Using @code{#ifdef}, as above, is the preferred way to do this,
+but sometimes that gets convoluted, in which case use
+
+@example
+#ifndef SPECIAL_FOO_HANDLING
+#define SPECIAL_FOO_HANDLING(pc, sp) (0)
+#endif
+@end example
+
+where the macro is used or in an appropriate header file.
+
+Whether to include a @dfn{small} hook, a hook around the exact pieces of
+code which are system-dependent, or whether to replace a whole function
+with a hook depends on the case. A good example of this dilemma can be
+found in @code{get_saved_register}. All machines that GDB 2.8 ran on
+just needed the @code{FRAME_FIND_SAVED_REGS} hook to find the saved
+registers. Then the SPARC and Pyramid came along, and
+@code{HAVE_REGISTER_WINDOWS} and @code{REGISTER_IN_WINDOW_P} were
+introduced. Then the 29k and 88k required the @code{GET_SAVED_REGISTER}
+hook. The first three are examples of small hooks; the latter replaces
+a whole function. In this specific case, it is useful to have both
+kinds; it would be a bad idea to replace all the uses of the small hooks
+with @code{GET_SAVED_REGISTER}, since that would result in much
+duplicated code. Other times, duplicating a few lines of code here or
+there is much cleaner than introducing a large number of small hooks.
+
+Another way to generalize GDB along a particular interface is with an
+attribute struct. For example, GDB has been generalized to handle
+multiple kinds of remote interfaces -- not by #ifdef's everywhere, but
+by defining the "target_ops" structure and having a current target (as
+well as a stack of targets below it, for memory references). Whenever
+something needs to be done that depends on which remote interface we are
+using, a flag in the current target_ops structure is tested (e.g.
+`target_has_stack'), or a function is called through a pointer in the
+current target_ops structure. In this way, when a new remote interface
+is added, only one module needs to be touched -- the one that actually
+implements the new remote interface. Other examples of
+attribute-structs are BFD access to multiple kinds of object file
+formats, or GDB's access to multiple source languages.
+
+Please avoid duplicating code. For example, in GDB 3.x all the code
+interfacing between @code{ptrace} and the rest of GDB was duplicated in
+@file{*-dep.c}, and so changing something was very painful. In GDB 4.x,
+these have all been consolidated into @file{infptrace.c}.
+@file{infptrace.c} can deal with variations between systems the same way
+any system-independent file would (hooks, #if defined, etc.), and
+machines which are radically different don't need to use infptrace.c at
+all.
+
+Don't put debugging printfs in the code.
+
+@node Porting GDB
+
+@chapter Porting GDB
+
+Most of the work in making GDB compile on a new machine is in specifying
+the configuration of the machine. This is done in a dizzying variety of
+header files and configuration scripts, which we hope to make more
+sensible soon. Let's say your new host is called an @var{xyz} (e.g.
+@samp{sun4}), and its full three-part configuration name is
+@code{@var{arch}-@var{xvend}-@var{xos}} (e.g. @samp{sparc-sun-sunos4}).
+In particular:
+
+In the top level directory, edit @file{config.sub} and add @var{arch},
+@var{xvend}, and @var{xos} to the lists of supported architectures,
+vendors, and operating systems near the bottom of the file. Also, add
+@var{xyz} as an alias that maps to
+@code{@var{arch}-@var{xvend}-@var{xos}}. You can test your changes by
+running
+
+@example
+./config.sub @var{xyz}
+@end example
+@noindent
+and
+@example
+./config.sub @code{@var{arch}-@var{xvend}-@var{xos}}
+@end example
+@noindent
+which should both respond with @code{@var{arch}-@var{xvend}-@var{xos}}
+and no error messages.
+
+You need to port BFD, if that hasn't been done already. Porting BFD is
+beyond the scope of this manual.
+
+To configure GDB itself, edit @file{gdb/configure.host} to recognize
+your system and set @code{gdb_host} to @var{xyz}, and (unless your
+desired target is already available) also edit @file{gdb/configure.tgt},
+setting @code{gdb_target} to something appropriate (for instance,
+@var{xyz}).
+
+Finally, you'll need to specify and define GDB's host-, native-, and
+target-dependent @file{.h} and @file{.c} files used for your
+configuration.
+
+@section Configuring GDB for Release
+
+From the top level directory (containing @file{gdb}, @file{bfd},
+@file{libiberty}, and so on):
+@example
+make -f Makefile.in gdb.tar.gz
+@end example
+
+This will properly configure, clean, rebuild any files that are
+distributed pre-built (e.g. @file{c-exp.tab.c} or @file{refcard.ps}),
+and will then make a tarfile. (If the top level directory has already
+been configured, you can just do @code{make gdb.tar.gz} instead.)
+
+This procedure requires:
+@itemize @bullet
+@item symbolic links
+@item @code{makeinfo} (texinfo2 level)
+@item @TeX{}
+@item @code{dvips}
+@item @code{yacc} or @code{bison}
+@end itemize
+@noindent
+@dots{} and the usual slew of utilities (@code{sed}, @code{tar}, etc.).
+
+@subheading TEMPORARY RELEASE PROCEDURE FOR DOCUMENTATION
+
+@file{gdb.texinfo} is currently marked up using the texinfo-2 macros,
+which are not yet a default for anything (but we have to start using
+them sometime).
+
+For making paper, the only thing this implies is the right generation of
+@file{texinfo.tex} needs to be included in the distribution.
+
+For making info files, however, rather than duplicating the texinfo2
+distribution, generate @file{gdb-all.texinfo} locally, and include the
+files @file{gdb.info*} in the distribution. Note the plural;
+@code{makeinfo} will split the document into one overall file and five
+or so included files.
+
+@node Testsuite
+
+@chapter Testsuite
+
+The testsuite is an important component of the GDB package. While it is
+always worthwhile to encourage user testing, in practice this is rarely
+sufficient; users typically use only a small subset of the available
+commands, and it has proven all too common for a change to cause a
+significant regression that went unnoticed for some time.
+
+The GDB testsuite uses the DejaGNU testing framework. DejaGNU is built
+using tcl and expect. The tests themselves are calls to various tcl
+procs; the framework runs all the procs and summarizes the passes and
+fails.
+
+@section Using the Testsuite
+
+To run the testsuite, simply go to the GDB object directory (or to the
+testsuite's objdir) and type @code{make check}. This just sets up some
+environment variables and invokes DejaGNU's @code{runtest} script. While
+the testsuite is running, you'll get mentions of which test file is in use,
+and a mention of any unexpected passes or fails. When the testsuite is
+finished, you'll get a summary that looks like this:
+@example
+ === gdb Summary ===
+
+# of expected passes 6016
+# of unexpected failures 58
+# of unexpected successes 5
+# of expected failures 183
+# of unresolved testcases 3
+# of untested testcases 5
+@end example
+The ideal test run consists of expected passes only; however, reality
+conspires to keep us from this ideal. Unexpected failures indicate
+real problems, whether in GDB or in the testsuite. Expected failures
+are still failures, but ones which have been decided are too hard to
+deal with at the time; for instance, a test case might work everywhere
+except on AIX, and there is no prospect of the AIX case being fixed in
+the near future. Expected failures should not be added lightly, since
+you may be masking serious bugs in GDB. Unexpected successes are expected
+fails that are passing for some reason, while unresolved and untested
+cases often indicate some minor catastrophe, such as the compiler being
+unable to deal with a test program.
+
+When making any significant change to GDB, you should run the testsuite
+before and after the change, to confirm that there are no regressions.
+Note that truly complete testing would require that you run the
+testsuite with all supported configurations and a variety of compilers;
+however this is more than really necessary. In many cases testing with
+a single configuration is sufficient. Other useful options are to test
+one big-endian (Sparc) and one little-endian (x86) host, a cross config
+with a builtin simulator (powerpc-eabi, mips-elf), or a 64-bit host
+(Alpha).
+
+If you add new functionality to GDB, please consider adding tests for it
+as well; this way future GDB hackers can detect and fix their changes
+that break the functionality you added. Similarly, if you fix a bug
+that was not previously reported as a test failure, please add a test
+case for it. Some cases are extremely difficult to test, such as code
+that handles host OS failures or bugs in particular versions of
+compilers, and it's OK not to try to write tests for all of those.
+
+@section Testsuite Organization
+
+The testsuite is entirely contained in @file{gdb/testsuite}. While the
+testsuite includes some makefiles and configury, these are very minimal,
+and used for little besides cleaning up, since the tests themselves
+handle the compilation of the programs that GDB will run. The file
+@file{testsuite/lib/gdb.exp} contains common utility procs useful for
+all GDB tests, while the directory @file{testsuite/config} contains
+configuration-specific files, typically used for special-purpose
+definitions of procs like @code{gdb_load} and @code{gdb_start}.
+
+The tests themselves are to be found in @file{testsuite/gdb.*} and
+subdirectories of those. The names of the test files must always end
+with @file{.exp}. DejaGNU collects the test files by wildcarding
+in the test directories, so both subdirectories and individual files
+get chosen and run in alphabetical order.
+
+The following table lists the main types of subdirectories and what they
+are for. Since DejaGNU finds test files no matter where they are
+located, and since each test file sets up its own compilation and
+execution environment, this organization is simply for convenience and
+intelligibility.
+
+@table @code
+
+@item gdb.base
+
+This is the base testsuite. The tests in it should apply to all
+configurations of GDB (but generic native-only tests may live here).
+The test programs should be in the subset of C that is valid K&R,
+ANSI/ISO, and C++ (ifdefs are allowed if necessary, for instance
+for prototypes).
+
+@item gdb.@var{lang}
+
+Language-specific tests for all languages besides C. Examples are
+@file{gdb.c++} and @file{gdb.java}.
+
+@item gdb.@var{platform}
+
+Non-portable tests. The tests are specific to a specific configuration
+(host or target), such as HP-UX or eCos. Example is @file{gdb.hp}, for
+HP-UX.
+
+@item gdb.@var{compiler}
+
+Tests specific to a particular compiler. As of this writing (June
+1999), there aren't currently any groups of tests in this category that
+couldn't just as sensibly be made platform-specific, but one could
+imagine a gdb.gcc, for tests of GDB's handling of GCC extensions.
+
+@item gdb.@var{subsystem}
+
+Tests that exercise a specific GDB subsystem in more depth. For
+instance, @file{gdb.disasm} exercises various disassemblers, while
+@file{gdb.stabs} tests pathways through the stabs symbol reader.
+
+@end table
+
+@section Writing Tests
+
+In many areas, the GDB tests are already quite comprehensive; you
+should be able to copy existing tests to handle new cases.
+
+You should try to use @code{gdb_test} whenever possible, since it
+includes cases to handle all the unexpected errors that might happen.
+However, it doesn't cost anything to add new test procedures; for
+instance, @file{gdb.base/exprs.exp} defines a @code{test_expr} that
+calls @code{gdb_test} multiple times.
+
+Only use @code{send_gdb} and @code{gdb_expect} when absolutely
+necessary, such as when GDB has several valid responses to a command.
+
+The source language programs do @emph{not} need to be in a consistent
+style. Since GDB is used to debug programs written in many different
+styles, it's worth having a mix of styles in the testsuite; for
+instance, some GDB bugs involving the display of source lines would
+never manifest themselves if the programs used GNU coding style
+uniformly.
+
+@node Hints
+
+@chapter Hints
+
+Check the @file{README} file, it often has useful information that does not
+appear anywhere else in the directory.
+
+@menu
+* Getting Started:: Getting started working on GDB
+* Debugging GDB:: Debugging GDB with itself
+@end menu
+
+@node Getting Started,,, Hints
+
+@section Getting Started
+
+GDB is a large and complicated program, and if you first starting to
+work on it, it can be hard to know where to start. Fortunately, if you
+know how to go about it, there are ways to figure out what is going on.
+
+This manual, the GDB Internals manual, has information which applies
+generally to many parts of GDB.
+
+Information about particular functions or data structures are located in
+comments with those functions or data structures. If you run across a
+function or a global variable which does not have a comment correctly
+explaining what is does, this can be thought of as a bug in GDB; feel
+free to submit a bug report, with a suggested comment if you can figure
+out what the comment should say. If you find a comment which is
+actually wrong, be especially sure to report that.
+
+Comments explaining the function of macros defined in host, target, or
+native dependent files can be in several places. Sometimes they are
+repeated every place the macro is defined. Sometimes they are where the
+macro is used. Sometimes there is a header file which supplies a
+default definition of the macro, and the comment is there. This manual
+also documents all the available macros.
+@c (@pxref{Host Conditionals}, @pxref{Target
+@c Conditionals}, @pxref{Native Conditionals}, and @pxref{Obsolete
+@c Conditionals})
+
+Start with the header files. Once you some idea of how GDB's internal
+symbol tables are stored (see @file{symtab.h}, @file{gdbtypes.h}), you
+will find it much easier to understand the code which uses and creates
+those symbol tables.
+
+You may wish to process the information you are getting somehow, to
+enhance your understanding of it. Summarize it, translate it to another
+language, add some (perhaps trivial or non-useful) feature to GDB, use
+the code to predict what a test case would do and write the test case
+and verify your prediction, etc. If you are reading code and your eyes
+are starting to glaze over, this is a sign you need to use a more active
+approach.
+
+Once you have a part of GDB to start with, you can find more
+specifically the part you are looking for by stepping through each
+function with the @code{next} command. Do not use @code{step} or you
+will quickly get distracted; when the function you are stepping through
+calls another function try only to get a big-picture understanding
+(perhaps using the comment at the beginning of the function being
+called) of what it does. This way you can identify which of the
+functions being called by the function you are stepping through is the
+one which you are interested in. You may need to examine the data
+structures generated at each stage, with reference to the comments in
+the header files explaining what the data structures are supposed to
+look like.
+
+Of course, this same technique can be used if you are just reading the
+code, rather than actually stepping through it. The same general
+principle applies---when the code you are looking at calls something
+else, just try to understand generally what the code being called does,
+rather than worrying about all its details.
+
+A good place to start when tracking down some particular area is with a
+command which invokes that feature. Suppose you want to know how
+single-stepping works. As a GDB user, you know that the @code{step}
+command invokes single-stepping. The command is invoked via command
+tables (see @file{command.h}); by convention the function which actually
+performs the command is formed by taking the name of the command and
+adding @samp{_command}, or in the case of an @code{info} subcommand,
+@samp{_info}. For example, the @code{step} command invokes the
+@code{step_command} function and the @code{info display} command invokes
+@code{display_info}. When this convention is not followed, you might
+have to use @code{grep} or @kbd{M-x tags-search} in emacs, or run GDB on
+itself and set a breakpoint in @code{execute_command}.
+
+If all of the above fail, it may be appropriate to ask for information
+on @code{bug-gdb}. But @emph{never} post a generic question like ``I was
+wondering if anyone could give me some tips about understanding
+GDB''---if we had some magic secret we would put it in this manual.
+Suggestions for improving the manual are always welcome, of course.
+
+@node Debugging GDB,,,Hints
+
+@section Debugging GDB with itself
+
+If GDB is limping on your machine, this is the preferred way to get it
+fully functional. Be warned that in some ancient Unix systems, like
+Ultrix 4.2, a program can't be running in one process while it is being
+debugged in another. Rather than typing the command @code{@w{./gdb
+./gdb}}, which works on Suns and such, you can copy @file{gdb} to
+@file{gdb2} and then type @code{@w{./gdb ./gdb2}}.
+
+When you run GDB in the GDB source directory, it will read a
+@file{.gdbinit} file that sets up some simple things to make debugging
+gdb easier. The @code{info} command, when executed without a subcommand
+in a GDB being debugged by gdb, will pop you back up to the top level
+gdb. See @file{.gdbinit} for details.
+
+If you use emacs, you will probably want to do a @code{make TAGS} after
+you configure your distribution; this will put the machine dependent
+routines for your local machine where they will be accessed first by
+@kbd{M-.}
+
+Also, make sure that you've either compiled GDB with your local cc, or
+have run @code{fixincludes} if you are compiling with gcc.
+
+@section Submitting Patches
+
+Thanks for thinking of offering your changes back to the community of
+GDB users. In general we like to get well designed enhancements.
+Thanks also for checking in advance about the best way to transfer the
+changes.
+
+The GDB maintainers will only install ``cleanly designed'' patches.
+This manual summarizes what we believe to be clean design for GDB.
+
+If the maintainers don't have time to put the patch in when it arrives,
+or if there is any question about a patch, it goes into a large queue
+with everyone else's patches and bug reports.
+
+The legal issue is that to incorporate substantial changes requires a
+copyright assignment from you and/or your employer, granting ownership
+of the changes to the Free Software Foundation. You can get the
+standard documents for doing this by sending mail to @code{gnu@@gnu.org}
+and asking for it. We recommend that people write in "All programs
+owned by the Free Software Foundation" as "NAME OF PROGRAM", so that
+changes in many programs (not just GDB, but GAS, Emacs, GCC, etc) can be
+contributed with only one piece of legalese pushed through the
+bureacracy and filed with the FSF. We can't start merging changes until
+this paperwork is received by the FSF (their rules, which we follow
+since we maintain it for them).
+
+Technically, the easiest way to receive changes is to receive each
+feature as a small context diff or unidiff, suitable for "patch". Each
+message sent to me should include the changes to C code and header files
+for a single feature, plus ChangeLog entries for each directory where
+files were modified, and diffs for any changes needed to the manuals
+(gdb/doc/gdb.texinfo or gdb/doc/gdbint.texinfo). If there are a lot of
+changes for a single feature, they can be split down into multiple
+messages.
+
+In this way, if we read and like the feature, we can add it to the
+sources with a single patch command, do some testing, and check it in.
+If you leave out the ChangeLog, we have to write one. If you leave
+out the doc, we have to puzzle out what needs documenting. Etc.
+
+The reason to send each change in a separate message is that we will not
+install some of the changes. They'll be returned to you with questions
+or comments. If we're doing our job correctly, the message back to you
+will say what you have to fix in order to make the change acceptable.
+The reason to have separate messages for separate features is so that
+the acceptable changes can be installed while one or more changes are
+being reworked. If multiple features are sent in a single message, we
+tend to not put in the effort to sort out the acceptable changes from
+the unacceptable, so none of the features get installed until all are
+acceptable.
+
+If this sounds painful or authoritarian, well, it is. But we get a lot
+of bug reports and a lot of patches, and many of them don't get
+installed because we don't have the time to finish the job that the bug
+reporter or the contributor could have done. Patches that arrive
+complete, working, and well designed, tend to get installed on the day
+they arrive. The others go into a queue and get installed as time
+permits, which, since the maintainers have many demands to meet, may not
+be for quite some time.
+
+Please send patches directly to the GDB maintainers at
+@code{gdb-patches@@sourceware.cygnus.com}.
+
+@section Obsolete Conditionals
+
+Fragments of old code in GDB sometimes reference or set the following
+configuration macros. They should not be used by new code, and old uses
+should be removed as those parts of the debugger are otherwise touched.
+
+@table @code
-This makes a cleanup which will cause FUNCTION to be called with ARG
-(a char *) later. The result, OLD_CHAIN, is a handle that can be
-passed to do_cleanups or discard_cleanups later. Unless you are
-going to call do_cleanups or discard_cleanups yourself,
-you can ignore the result from make_cleanup.
+@item STACK_END_ADDR
+This macro used to define where the end of the stack appeared, for use
+in interpreting core file formats that don't record this address in the
+core file itself. This information is now configured in BFD, and GDB
+gets the info portably from there. The values in GDB's configuration
+files should be moved into BFD configuration files (if needed there),
+and deleted from all of GDB's config files.
- do_cleanups (old_chain);
+Any @file{@var{foo}-xdep.c} file that references STACK_END_ADDR
+is so old that it has never been converted to use BFD. Now that's old!
-Performs all cleanups done since make_cleanup returned OLD_CHAIN.
-E.g.: make_cleanup (a, 0); old = make_cleanup (b, 0); do_cleanups (old);
-will call b() but will not call a(). The cleanup that calls a() will remain
-in the cleanup chain, and will be done later unless otherwise discarded.
+@item PYRAMID_CONTROL_FRAME_DEBUGGING
+pyr-xdep.c
+@item PYRAMID_CORE
+pyr-xdep.c
+@item PYRAMID_PTRACE
+pyr-xdep.c
- discard_cleanups (old_chain);
+@item REG_STACK_SEGMENT
+exec.c
-Same as do_cleanups except that it just removes the cleanups from the
-chain and does not call the specified functions.
+@end table
-Some functions, e.g. fputs_filtered() or error(), specify that they
-"should not be called when cleanups are not in place". This means
-that any actions you need to reverse in the case of an error or
-interruption must be on the cleanup chain before you call these functions,
-since they might never return to your code (they "longjmp" instead).
+@contents
+@bye
projects / thirdparty / binutils-gdb.git / blobdiff