-@c Copyright (C) 1988-2019 Free Software Foundation, Inc.
+@c Copyright (C) 1988-2020 Free Software Foundation, Inc.
@c This is part of the GCC manual.
@c For copying conditions, see the file gcc.texi.
@c man end
@c man begin COPYRIGHT
-Copyright @copyright{} 1988-2019 Free Software Foundation, Inc.
+Copyright @copyright{} 1988-2020 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
-Wabi=@var{n} -Wabi-tag -Wcomma-subscript -Wconversion-null @gol
-Wctor-dtor-privacy @gol
-Wdelete-non-virtual-dtor -Wdeprecated-copy -Wdeprecated-copy-dtor @gol
--Wliteral-suffix @gol
+-Wliteral-suffix -Wmismatched-tags @gol
-Wmultiple-inheritance -Wno-init-list-lifetime @gol
-Wnamespaces -Wnarrowing @gol
--Wpessimizing-move -Wredundant-move @gol
+-Wpessimizing-move -Wredundant-move -Wredundant-tags @gol
-Wnoexcept -Wnoexcept-type -Wclass-memaccess @gol
-Wnon-virtual-dtor -Wreorder -Wregister @gol
-Weffc++ -Wstrict-null-sentinel -Wtemplates @gol
@gccoptlist{-fmessage-length=@var{n} @gol
-fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]} @gol
-fdiagnostics-color=@r{[}auto@r{|}never@r{|}always@r{]} @gol
+-fdiagnostics-urls=@r{[}auto@r{|}never@r{|}always@r{]} @gol
-fdiagnostics-format=@r{[}text@r{|}json@r{]} @gol
-fno-diagnostics-show-option -fno-diagnostics-show-caret @gol
-fno-diagnostics-show-labels -fno-diagnostics-show-line-numbers @gol
+-fno-diagnostics-show-cwe @gol
-fdiagnostics-minimum-margin-width=@var{width} @gol
-fdiagnostics-parseable-fixits -fdiagnostics-generate-patch @gol
-fdiagnostics-show-template-tree -fno-elide-type @gol
-Wbool-compare -Wbool-operation @gol
-Wno-builtin-declaration-mismatch @gol
-Wno-builtin-macro-redefined -Wc90-c99-compat -Wc99-c11-compat @gol
+-Wc11-c2x-compat @gol
-Wc++-compat -Wc++11-compat -Wc++14-compat -Wc++17-compat @gol
-Wc++20-compat @gol
-Wcast-align -Wcast-align=strict -Wcast-function-type -Wcast-qual @gol
-Winaccessible-base @gol
-Winit-self -Winline -Wno-int-conversion -Wint-in-bool-context @gol
-Wno-int-to-pointer-cast -Winvalid-memory-model -Wno-invalid-offsetof @gol
+-Wzero-length-bounds @gol
-Winvalid-pch -Wlarger-than=@var{byte-size} @gol
-Wlogical-op -Wlogical-not-parentheses -Wlong-long @gol
-Wmain -Wmaybe-uninitialized -Wmemset-elt-size -Wmemset-transposed-args @gol
-Wno-pragmas -Wno-prio-ctor-dtor -Wredundant-decls @gol
-Wrestrict -Wno-return-local-addr @gol
-Wreturn-type -Wsequence-point -Wshadow -Wno-shadow-ivar @gol
--Wshadow=global, -Wshadow=local, -Wshadow=compatible-local @gol
+-Wshadow=global -Wshadow=local -Wshadow=compatible-local @gol
-Wshift-overflow -Wshift-overflow=@var{n} @gol
-Wshift-count-negative -Wshift-count-overflow -Wshift-negative-value @gol
-Wsign-compare -Wsign-conversion -Wfloat-conversion @gol
-Wsizeof-pointer-memaccess -Wsizeof-array-argument @gol
-Wstack-protector -Wstack-usage=@var{byte-size} -Wstrict-aliasing @gol
-Wstrict-aliasing=n -Wstrict-overflow -Wstrict-overflow=@var{n} @gol
+-Wstring-compare @gol
-Wstringop-overflow=@var{n} -Wstringop-truncation -Wsubobject-linkage @gol
-Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{|}malloc@r{]} @gol
-Wsuggest-final-types @gol -Wsuggest-final-methods -Wsuggest-override @gol
-falign-jumps[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
-falign-labels[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
-falign-loops[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
+-fno-allocation-dce -fallow-store-data-races @gol
-fassociative-math -fauto-profile -fauto-profile[=@var{path}] @gol
-fauto-inc-dec -fbranch-probabilities @gol
-fcaller-saves @gol
-fpartial-inlining -fpeel-loops -fpredictive-commoning @gol
-fprefetch-loop-arrays @gol
-fprofile-correction @gol
--fprofile-use -fprofile-use=@var{path} -fprofile-values @gol
--fprofile-reorder-functions @gol
+-fprofile-use -fprofile-use=@var{path} -fprofile-partial-training @gol
+-fprofile-values -fprofile-reorder-functions @gol
-freciprocal-math -free -frename-registers -freorder-blocks @gol
-freorder-blocks-algorithm=@var{algorithm} @gol
-freorder-blocks-and-partition -freorder-functions @gol
-fnon-call-exceptions -fdelete-dead-exceptions -funwind-tables @gol
-fasynchronous-unwind-tables @gol
-fno-gnu-unique @gol
--finhibit-size-directive -fno-common -fno-ident @gol
+-finhibit-size-directive -fcommon -fno-ident @gol
-fpcc-struct-return -fpic -fPIC -fpie -fPIE -fno-plt @gol
-fno-jump-tables @gol
-frecord-gcc-switches @gol
@item Developer Options
@xref{Developer Options,,GCC Developer Options}.
@gccoptlist{-d@var{letters} -dumpspecs -dumpmachine -dumpversion @gol
--dumpfullversion -fchecking -fchecking=@var{n} -fdbg-cnt-list @gol
--fdbg-cnt=@var{counter-value-list} @gol
+-dumpfullversion -fcallgraph-info@r{[}=su,da@r{]}
+-fchecking -fchecking=@var{n}
+-fdbg-cnt-list @gol -fdbg-cnt=@var{counter-value-list} @gol
-fdisable-ipa-@var{pass_name} @gol
-fdisable-rtl-@var{pass_name} @gol
-fdisable-rtl-@var{pass-name}=@var{range-list} @gol
@gccoptlist{-mmcu=@var{mcu} -mabsdata -maccumulate-args @gol
-mbranch-cost=@var{cost} @gol
-mcall-prologues -mgas-isr-prologues -mint8 @gol
+-mdouble=@var{bits} -mlong-double=@var{bits} @gol
-mn_flash=@var{size} -mno-interrupts @gol
-mmain-is-OS_task -mrelax -mrmw -mstrict-X -mtiny-stack @gol
-mfract-convert-truncate @gol
-mwarn-mcu @gol
-mcode-region= -mdata-region= @gol
-msilicon-errata= -msilicon-errata-warn= @gol
--mhwmult= -minrt}
+-mhwmult= -minrt -mtiny-printf}
@emph{NDS32 Options}
@gccoptlist{-mbig-endian -mlittle-endian @gol
Version 13, which first appeared in G++ 8.2, fixes the accidental
change in version 12.
+Version 14, which first appeared in G++ 10, corrects the mangling of
+the nullptr expression.
+
See also @option{-Wabi}.
@item -fabi-compat-version=@var{n}
@samp{new (nothrow)}.
@item -fconcepts
+@itemx -fconcepts-ts
@opindex fconcepts
-Enable support for the C++ Extensions for Concepts Technical
-Specification, ISO 19217 (2015), which allows code like
+@opindex fconcepts-ts
+Below @option{-std=c++2a}, @option{-fconcepts} enables support for the
+C++ Extensions for Concepts Technical Specification, ISO 19217 (2015).
-@smallexample
-template <class T> concept bool Addable = requires (T t) @{ t + t; @};
-template <Addable T> T add (T a, T b) @{ return a + b; @}
-@end smallexample
+With @option{-std=c++2a} and above, Concepts are part of the language
+standard, so @option{-fconcepts} defaults to on. But the standard
+specification of Concepts differs significantly from the TS, so some
+constructs that were allowed in the TS but didn't make it into the
+standard can still be enabled by @option{-fconcepts-ts}.
@item -fconstexpr-depth=@var{n}
@opindex fconstexpr-depth
This warning is enabled by @option{-Wextra}.
+@item -Wredundant-tags @r{(C++ and Objective-C++ only)}
+@opindex Wredundant-tags
+@opindex Wno-redundant-tags
+Warn about redundant class-key and enum-key in references to class types
+and enumerated types in contexts where the key can be eliminated without
+causing an ambiguity. For example
+
+@smallexample
+struct foo;
+struct foo *p; // -Wredundant-tags, keyword struct can be eliminated
+
+void foo (); // "hides" struct foo
+void bar (struct foo&); // no warning, keyword struct cannot be eliminated
+@end smallexample
+
@item -fext-numeric-literals @r{(C++ and Objective-C++ only)}
@opindex fext-numeric-literals
@opindex fno-ext-numeric-literals
one can still use the STL. One may also instantiate or specialize
templates.
+@item -Wmismatched-tags @r{(C++ and Objective-C++ only)}
+@opindex Wmismatched-tags
+@opindex Wno-mismatched-tags
+Warn for declarations of structs, classes, and class templates and their
+specializations with a class-key that does not match either the definition
+or the first declaration if no definition is provided.
+
+For example, the declaration of @code{struct Object} in the argument list
+of @code{draw} triggers the warning. To avoid it, either remove the redundant
+class-key @code{struct} or replace it with @code{class} to match its definition.
+@smallexample
+class Object @{
+public:
+ virtual ~Object () = 0;
+@};
+void draw (struct Object*);
+@end smallexample
+
+It is not wrong to declare a class with the class-key @code{struct} as
+the example above shows. The @option{-Wmismatched-tags} option is intended
+to help achieve a consistent style of class declarations. In code that is
+intended to be portable to Windows-based compilers the warning helps prevent
+unresolved references due to the difference in the mangling of symbols
+declared with different class-keys. The option can be used either on its
+own or in conjunction with @option{-Wredundant-tags}.
+
@item -Wmultiple-inheritance @r{(C++ and Objective-C++ only)}
@opindex Wmultiple-inheritance
@opindex Wno-multiple-inheritance
arguments in the C++ frontend.
@end table
+@item -fdiagnostics-urls[=@var{WHEN}]
+@opindex fdiagnostics-urls
+@cindex urls
+Use escape sequences to embed URLs in diagnostics. For example, when
+@option{-fdiagnostics-show-option} emits text showing the command-line
+option controlling a diagnostic, embed a URL for documentation of that
+option.
+
+@var{WHEN} is @samp{never}, @samp{always}, or @samp{auto}.
+The default is @samp{auto}, which means to use URL escape sequences only
+when the standard error is a terminal.
+
@item -fno-diagnostics-show-option
@opindex fno-diagnostics-show-option
@opindex fdiagnostics-show-option
This option suppresses the printing of these labels (in the example above,
the vertical bars and the ``char *'' and ``long int'' text).
+@item -fno-diagnostics-show-cwe
+@opindex fno-diagnostics-show-cwe
+@opindex fdiagnostics-show-cwe
+Diagnostic messages can optionally have an associated
+@url{https://cwe.mitre.org/index.html, CWE} identifier.
+GCC itself does not do this for any of its diagnostics, but plugins may do so.
+By default, if this information is present, it will be printed with
+the diagnostic. This option suppresses the printing of this metadata.
+
@item -fno-diagnostics-show-line-numbers
@opindex fno-diagnostics-show-line-numbers
@opindex fdiagnostics-show-line-numbers
],
"message": "this \u2018if\u2019 clause does not guard...",
"option": "-Wmisleading-indentation",
+ "option_url": "https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmisleading-indentation",
"children": [
@{
"kind": "note",
-Wimplicit-int @r{(C and Objective-C only)} @gol
-Wimplicit-function-declaration @r{(C and Objective-C only)} @gol
-Winit-self @r{(only for C++)} @gol
+-Wzero-length-bounds @gol
-Wlogical-not-parentheses @gol
-Wmain @r{(only for C/ObjC and unless} @option{-ffreestanding}@r{)} @gol
-Wmaybe-uninitialized @gol
-Wold-style-declaration @r{(C only)} @gol
-Woverride-init @gol
-Wsign-compare @r{(C only)} @gol
+-Wstring-compare @gol
-Wredundant-move @r{(only for C++)} @gol
-Wtype-limits @gol
-Wuninitialized @gol
@item -Wuninitialized
@opindex Wuninitialized
@opindex Wno-uninitialized
-Warn if an automatic variable is used without first being initialized
-or if a variable may be clobbered by a @code{setjmp} call. In C++,
-warn if a non-static reference or non-static @code{const} member
-appears in a class without constructors.
+Warn if an automatic variable is used without first being initialized.
+In C++, warn if a non-static reference or non-static @code{const}
+member appears in a class without constructors.
If you want to warn about code that uses the uninitialized value of the
variable in its own initializer, use the @option{-Winit-self} option.
-These warnings occur for individual uninitialized or clobbered
-elements of structure, union or array variables as well as for
-variables that are uninitialized or clobbered as a whole. They do
-not occur for variables or elements declared @code{volatile}. Because
-these warnings depend on optimization, the exact variables or elements
-for which there are warnings depends on the precise optimization
-options and version of GCC used.
+These warnings occur for individual uninitialized elements of
+structure, union or array variables as well as for variables that are
+uninitialized as a whole. They do not occur for variables or elements
+declared @code{volatile}. Because these warnings depend on
+optimization, the exact variables or elements for which there are
+warnings depend on the precise optimization options and version of GCC
+used.
Note that there may be no warning about a variable that is used only
to compute a value that itself is never used, because such
false positives.
@end table
+@item -Wstring-compare
+@opindex Wstring-compare
+@opindex Wno-string-compare
+Warn for calls to @code{strcmp} and @code{strncmp} whose result is
+determined to be either zero or non-zero in tests for such equality
+owing to the length of one argument being greater than the size of
+the array the other argument is stored in (or the bound in the case
+of @code{strncmp}). Such calls could be mistakes. For example,
+the call to @code{strcmp} below is diagnosed because its result is
+necessarily non-zero irrespective of the contents of the array @code{a}.
+
+@smallexample
+extern char a[4];
+void f (char *d)
+@{
+ strcpy (d, "string");
+ @dots{}
+ if (0 == strcmp (a, d)) // cannot be true
+ puts ("a and d are the same");
+@}
+@end smallexample
+
+@option{-Wstring-compare} is enabled by @option{-Wextra}.
+
@item -Wstringop-overflow
@itemx -Wstringop-overflow=@var{type}
@opindex Wstringop-overflow
@opindex Wno-discarded-array-qualifiers
@opindex Wdiscarded-array-qualifiers
Do not warn if type qualifiers on arrays which are pointer targets
-are being discarded. Typically, the compiler warns if a
+are being discarded. Typically, the compiler warns if a
@code{const int (*)[]} variable is passed to a function that
takes a @code{int (*)[]} parameter. This option can be used to
suppress such a warning.
conversions the warnings @option{-Wno-int-to-pointer-cast} and
@option{-Wno-pointer-to-int-cast} may be used.
+@item -Wzero-length-bounds
+@opindex Wzero-length-bounds
+@opindex Wzero-length-bounds
+Warn about accesses to elements of zero-length array members that might
+overlap other members of the same object. Declaring interior zero-length
+arrays is discouraged because accesses to them are undefined. See
+@xref{Zero Length}.
+
+For example, the first two stores in function @code{bad} are diagnosed
+because the array elements overlap the subsequent members @code{b} and
+@code{c}. The third store is diagnosed by @option{-Warray-bounds}
+because it is beyond the bounds of the enclosing object.
+
+@smallexample
+struct X @{ int a[0]; int b, c; @};
+struct X x;
+
+void bad (void)
+@{
+ x.a[0] = 0; // -Wzero-length-bounds
+ x.a[1] = 1; // -Wzero-length-bounds
+ x.a[2] = 2; // -Warray-bounds
+@}
+@end smallexample
+
+Option @option{-Wzero-length-bounds} is enabled by @option{-Warray-bounds}.
+
@item -Wno-div-by-zero
@opindex Wno-div-by-zero
@opindex Wdiv-by-zero
@opindex Wno-shadow
Warn whenever a local variable or type declaration shadows another
variable, parameter, type, class member (in C++), or instance variable
-(in Objective-C) or whenever a built-in function is shadowed. Note
+(in Objective-C) or whenever a built-in function is shadowed. Note
that in C++, the compiler warns if a local variable shadows an
explicit typedef, but not if it shadows a struct/class/enum.
+If this warning is enabled, it includes also all instances of
+local shadowing. This means that @option{-Wno-shadow=local}
+and @option{-Wno-shadow=compatible-local} are ignored when
+@option{-Wshadow} is used.
Same as @option{-Wshadow=global}.
@item -Wno-shadow-ivar @r{(Objective-C only)}
Objective-C method.
@item -Wshadow=global
-@opindex Wshadow=local
-The default for @option{-Wshadow}. Warns for any (global) shadowing.
+@opindex Wshadow=global
+Warn for any shadowing.
+Same as @option{-Wshadow}.
@item -Wshadow=local
@opindex Wshadow=local
Warn when a local variable shadows another local variable or parameter.
-This warning is enabled by @option{-Wshadow=global}.
@item -Wshadow=compatible-local
@opindex Wshadow=compatible-local
Warn when a local variable shadows another local variable or parameter
-whose type is compatible with that of the shadowing variable. In C++,
+whose type is compatible with that of the shadowing variable. In C++,
type compatibility here means the type of the shadowing variable can be
-converted to that of the shadowed variable. The creation of this flag
+converted to that of the shadowed variable. The creation of this flag
(in addition to @option{-Wshadow=local}) is based on the idea that when
a local variable shadows another one of incompatible type, it is most
likely intentional, not a bug or typo, as shown in the following example:
@end smallexample
Since the two variable @code{i} in the example above have incompatible types,
-enabling only @option{-Wshadow=compatible-local} will not emit a warning.
+enabling only @option{-Wshadow=compatible-local} does not emit a warning.
Because their types are incompatible, if a programmer accidentally uses one
-in place of the other, type checking will catch that and emit an error or
-warning. So not warning (about shadowing) in this case will not lead to
-undetected bugs. Use of this flag instead of @option{-Wshadow=local} can
+in place of the other, type checking is expected to catch that and emit an
+error or warning. Use of this flag instead of @option{-Wshadow=local} can
possibly reduce the number of warnings triggered by intentional shadowing.
+Note that this also means that shadowing @code{const char *i} by
+@code{char *i} does not emit a warning.
-This warning is enabled by @option{-Wshadow=local}.
+This warning is also enabled by @option{-Wshadow=local}.
@item -Wlarger-than=@var{byte-size}
@opindex Wlarger-than=
and so on. This option is independent of the standards mode. Warnings are
disabled in the expression that follows @code{__extension__}.
+@item -Wc11-c2x-compat @r{(C and Objective-C only)}
+@opindex Wc11-c2x-compat
+@opindex Wno-c11-c2x-compat
+Warn about features not present in ISO C11, but present in ISO C2X.
+For instance, warn about omitting the string in @code{_Static_assert},
+use of @samp{[[]]} syntax for attributes, use of decimal
+floating-point types, and so on. This option is independent of the
+standards mode. Warnings are disabled in the expression that follows
+@code{__extension__}.
+
@item -Wc++-compat @r{(C and Objective-C only)}
@opindex Wc++-compat
@opindex Wno-c++-compat
@opindex Wold-style-definition
@opindex Wno-old-style-definition
Warn if an old-style function definition is used. A warning is given
-even if there is a previous prototype.
+even if there is a previous prototype. A definition using @samp{()}
+is not considered an old-style definition in C2X mode, because it is
+equivalent to @samp{(void)} in that case, but is considered an
+old-style definition for older standards.
@item -Wmissing-parameter-type @r{(C and Objective-C only)}
@opindex Wmissing-parameter-type
would be rendered unable to decode location lists using it.
@item -ginternal-reset-location-views
-@itemx -gnointernal-reset-location-views
+@itemx -gno-internal-reset-location-views
@opindex ginternal-reset-location-views
@opindex gno-internal-reset-location-views
Attempt to determine location views that can be omitted from location
Disregard strict standards compliance. @option{-Ofast} enables all
@option{-O3} optimizations. It also enables optimizations that are not
valid for all standard-compliant programs.
-It turns on @option{-ffast-math} and the Fortran-specific
-@option{-fstack-arrays}, unless @option{-fmax-stack-var-size} is
-specified, and @option{-fno-protect-parens}.
+It turns on @option{-ffast-math}, @option{-fallow-store-data-races}
+and the Fortran-specific @option{-fstack-arrays}, unless
+@option{-fmax-stack-var-size} is specified, and @option{-fno-protect-parens}.
@item -Og
@opindex Og
@item -ftree-loop-distribute-patterns
@opindex ftree-loop-distribute-patterns
Perform loop distribution of patterns that can be code generated with
-calls to a library. This flag is enabled by default at @option{-O3}, and
-by @option{-fprofile-use} and @option{-fauto-profile}.
+calls to a library. This flag is enabled by default at @option{-O2} and
+higher, and by @option{-fprofile-use} and @option{-fauto-profile}.
This pass distributes the initialization loops and generates a call to
memset zero. For example, the loop
Enabled at levels @option{-O2}, @option{-O3}.
+@item -fno-allocation-dce
+@opindex fno-allocation-dce
+Do not remove unused C++ allocations in dead code elimination.
+
+@item -fallow-store-data-races
+@opindex fallow-store-data-races
+Allow the compiler to introduce new data races on stores.
+
+Enabled at level @option{-Ofast}.
+
@item -funit-at-a-time
@opindex funit-at-a-time
This option is left for compatibility reasons. @option{-funit-at-a-time}
over @option{-ffp-contract=fast}. You can override them at link time.
To enable debug info generation you need to supply @option{-g} at
-compile-time. If any of the input files at link time were built
+compile time. If any of the input files at link time were built
with debug info generation enabled the link will enable debug info
generation as well. Any elaborate debug info settings
like the dwarf level @option{-gdwarf-5} need to be explicitly repeated
This option is enabled by @option{-fauto-profile}.
+@item -fprofile-partial-training
+@opindex fprofile-use
+With @code{-fprofile-use} all portions of programs not executed during train
+run are optimized agressively for size rather than speed. In some cases it is
+not practical to train all possible hot paths in the program. (For
+example, program may contain functions specific for a given hardware and
+trianing may not cover all hardware configurations program is run on.) With
+@code{-fprofile-partial-training} profile feedback will be ignored for all
+functions not executed during the train run leading them to be optimized as if
+they were compiled without profile feedback. This leads to better performance
+when train run is not representative but also leads to significantly bigger
+code.
+
@item -fprofile-use
@itemx -fprofile-use=@var{path}
@opindex fprofile-use
double} variants, to generate code that raises the ``inexact''
floating-point exception for noninteger arguments. ISO C99 and C11
allow these functions to raise the ``inexact'' exception, but ISO/IEC
-TS 18661-1:2014, the C bindings to IEEE 754-2008, does not allow these
-functions to do so.
+TS 18661-1:2014, the C bindings to IEEE 754-2008, as integrated into
+ISO C2X, does not allow these functions to do so.
The default is @option{-ffp-int-builtin-inexact}, allowing the
-exception to be raised. This option does nothing unless
-@option{-ftrapping-math} is in effect.
+exception to be raised, unless C2X or a later C standard is selected.
+This option does nothing unless @option{-ftrapping-math} is in effect.
Even if @option{-fno-fp-int-builtin-inexact} is used, if the functions
generate a call to a library function then the ``inexact'' exception
In order to get minimal, maximal and default value of a parameter,
one can use @option{--help=param -Q} options.
-In each case, the @var{value} is an integer. The allowable choices for
-@var{name} are:
+In each case, the @var{value} is an integer. The following choices
+of @var{name} are recognized for all targets:
@table @gcctabopt
@item predictable-branch-outcome
compilation time.
@item max-inline-insns-single
-@item max-inline-insns-single-O2
Several parameters control the tree inliner used in GCC@. This number sets the
maximum number of instructions (counted in GCC's internal representation) in a
single function that the tree inliner considers for inlining. This only
affects functions declared inline and methods implemented in a class
declaration (C++).
-For functions compiled with optimization levels
-@option{-O3} and @option{-Ofast} parameter @option{max-inline-insns-single} is
-applied. In other cases @option{max-inline-insns-single-O2} is applied.
-
@item max-inline-insns-auto
-@item max-inline-insns-auto-O2
When you use @option{-finline-functions} (included in @option{-O3}),
a lot of functions that would otherwise not be considered for inlining
by the compiler are investigated. To those functions, a different
(more restrictive) limit compared to functions declared inline can
-be applied.
-
-For functions compiled with optimization levels
-@option{-O3} and @option{-Ofast} parameter @option{max-inline-insns-auto} is
-applied. In other cases @option{max-inline-insns-auto-O2} is applied.
+be applied (@option{--param max-inline-insns-auto}).
@item max-inline-insns-small
This is bound applied to calls which are considered relevant with
Extra time accounted by inliner for function overhead such as time needed to
execute function prologue and epilogue
+@item inline-heuristics-hint-percent
+The scale (in percents) applied to @option{inline-insns-single},
+@option{inline-insns-single-O2}, @option{inline-insns-auto}
+when inline heuristics hints that inlining is
+very profitable (will enable later optimizations).
+
@item uninlined-thunk-insns
@item uninlined-thunk-time
Same as @option{--param uninlined-function-insns} and
@option{--param uninlined-function-time} but applied to function thunks
@item inline-min-speedup
-@item inline-min-speedup-O2
When estimated performance improvement of caller + callee runtime exceeds this
threshold (in percent), the function can be inlined regardless of the limit on
@option{--param max-inline-insns-single} and @option{--param
max-inline-insns-auto}.
-For functions compiled with optimization levels
-@option{-O3} and @option{-Ofast} parameter @option{inline-min-speedup} is
-applied. In other cases @option{inline-min-speedup-O2} is applied.
-
@item large-function-insns
The limit specifying really large functions. For functions larger than this
limit after inlining, inlining is constrained by
expressions whose probability exceeds the given threshold (in percents).
@item early-inlining-insns
-@item early-inlining-insns-O2
Specify growth that the early inliner can make. In effect it increases
the amount of inlining for code having a large abstraction penalty.
-For functions compiled with optimization levels
-@option{-O3} and @option{-Ofast} parameter @option{early-inlining-insns} is
-applied. In other cases @option{early-inlining-insns-O2} is applied.
-
@item max-early-inliner-iterations
Limit of iterations of the early inliner. This basically bounds
the number of nested indirect calls the early inliner can resolve.
@item lim-expensive
The minimum cost of an expensive expression in the loop invariant motion.
+@item min-loop-cond-split-prob
+When FDO profile information is available, @option{min-loop-cond-split-prob}
+specifies minimum threshold for probability of semi-invariant condition
+statement to trigger loop split.
+
@item iv-consider-all-candidates-bound
Bound on number of candidates for induction variables, below which
all candidates are considered for each use in induction variable
and performs those cloning opportunities with scores that exceed
@option{ipa-cp-eval-threshold}.
+@item ipa-cp-max-recursive-depth
+Maximum depth of recursive cloning for self-recursive function.
+
+@item ipa-cp-min-recursive-probability
+Recursive cloning only when the probability of call being executed exceeds
+the parameter.
+
@item ipa-cp-recursion-penalty
Percentage penalty the recursive functions will receive when they
are evaluated for cloning.
predicate, which is used to estimate cloning benefit, for default case
of the switch statement.
+@item ipa-max-param-expr-ops
+IPA-CP will analyze conditional statement that references some function
+parameter to estimate benefit for cloning upon certain constant value.
+But if number of operations in a parameter expression exceeds
+@option{ipa-max-param-expr-ops}, the expression is treated as complicated
+one, and is not handled by IPA analysis.
+
@item lto-partitions
Specify desired number of partitions produced during WHOPR compilation.
The number of partitions should exceed the number of CPUs used for compilation.
if either vectorization (@option{-ftree-vectorize}) or if-conversion
(@option{-ftree-loop-if-convert}) is disabled.
-@item allow-store-data-races
-Allow optimizers to introduce new data races on stores.
-Set to 1 to allow, otherwise to 0.
-
@item case-values-threshold
The smallest number of different values for which it is best to use a
jump-table instead of a tree of conditional branches. If the value is
diagnostics.
@end table
+
+The following choices of @var{name} are available on AArch64 targets:
+
+@table @gcctabopt
+@item aarch64-sve-compare-costs
+When vectorizing for SVE, consider using ``unpacked'' vectors for
+smaller elements and use the cost model to pick the cheapest approach.
+Also use the cost model to choose between SVE and Advanced SIMD vectorization.
+
+Using unpacked vectors includes storing smaller elements in larger
+containers and accessing elements with extending loads and truncating
+stores.
+@end table
+
@end table
@node Instrumentation Options
Emit extra code to check for buffer overflows, such as stack smashing
attacks. This is done by adding a guard variable to functions with
vulnerable objects. This includes functions that call @code{alloca}, and
-functions with buffers larger than 8 bytes. The guards are initialized
-when a function is entered and then checked when the function exits.
-If a guard check fails, an error message is printed and the program exits.
+functions with buffers larger than or equal to 8 bytes. The guards are
+initialized when a function is entered and then checked when the function
+exits. If a guard check fails, an error message is printed and the program
+exits. Only variables that are actually allocated on the stack are
+considered, optimized away variables or variables allocated in registers
+don't count.
@item -fstack-protector-all
@opindex fstack-protector-all
@opindex fstack-protector-strong
Like @option{-fstack-protector} but includes additional functions to
be protected --- those that have local array definitions, or have
-references to local frame addresses.
+references to local frame addresses. Only variables that are actually
+allocated on the stack are considered, optimized away variables or variables
+allocated in registers don't count.
@item -fstack-protector-explicit
@opindex fstack-protector-explicit
code that is not binary compatible with code generated without that switch.
Use it to conform to a non-default application binary interface.
-@item -fno-common
-@opindex fno-common
+@item -fcommon
@opindex fcommon
+@opindex fno-common
@cindex tentative definitions
-In C code, this option controls the placement of global variables
-defined without an initializer, known as @dfn{tentative definitions}
-in the C standard. Tentative definitions are distinct from declarations
+In C code, this option controls the placement of global variables
+defined without an initializer, known as @dfn{tentative definitions}
+in the C standard. Tentative definitions are distinct from declarations
of a variable with the @code{extern} keyword, which do not allocate storage.
-Unix C compilers have traditionally allocated storage for
-uninitialized global variables in a common block. This allows the
-linker to resolve all tentative definitions of the same variable
+The default is @option{-fno-common}, which specifies that the compiler places
+uninitialized global variables in the BSS section of the object file.
+This inhibits the merging of tentative definitions by the linker so you get a
+multiple-definition error if the same variable is accidentally defined in more
+than one compilation unit.
+
+The @option{-fcommon} places uninitialized global variables in a common block.
+This allows the linker to resolve all tentative definitions of the same variable
in different compilation units to the same object, or to a non-tentative
-definition.
-This is the behavior specified by @option{-fcommon}, and is the default for
-GCC on most targets.
-On the other hand, this behavior is not required by ISO
-C, and on some targets may carry a speed or code size penalty on
-variable references.
-
-The @option{-fno-common} option specifies that the compiler should instead
-place uninitialized global variables in the BSS section of the object file.
-This inhibits the merging of tentative definitions by the linker so
-you get a multiple-definition error if the same
-variable is defined in more than one compilation unit.
-Compiling with @option{-fno-common} is useful on targets for which
-it provides better performance, or if you wish to verify that the
-program will work on other systems that always treat uninitialized
-variable definitions this way.
+definition. This behavior is inconsistent with C++, and on many targets implies
+a speed and code size penalty on global variable references. It is mainly
+useful to enable legacy code to link without errors.
@item -fno-ident
@opindex fno-ident
@table @gcctabopt
+@item -fcallgraph-info
+@itemx -fcallgraph-info=@var{MARKERS}
+@opindex fcallgraph-info
+Makes the compiler output callgraph information for the program, on a
+per-object-file basis. The information is generated in the common VCG
+format. It can be decorated with additional, per-node and/or per-edge
+information, if a list of comma-separated markers is additionally
+specified. When the @code{su} marker is specified, the callgraph is
+decorated with stack usage information; it is equivalent to
+@option{-fstack-usage}. When the @code{da} marker is specified, the
+callgraph is decorated with information about dynamically allocated
+objects.
+
+When compiling with @option{-flto}, no callgraph information is output
+along with the object file. At LTO link time, @option{-fcallgraph-info}
+may generate multiple callgraph information files next to intermediate
+LTO output files.
+
@item -d@var{letters}
@itemx -fdump-rtl-@var{pass}
@itemx -fdump-rtl-@var{pass}=@var{filename}
@item -fdbg-cnt=@var{counter-value-list}
@opindex fdbg-cnt
Set the internal debug counter lower and upper bound. @var{counter-value-list}
-is a comma-separated list of @var{name}:@var{lower_bound}:@var{upper_bound}
-tuples which sets the lower and the upper bound of each debug
-counter @var{name}. The @var{lower_bound} is optional and is zero
+is a comma-separated list of @var{name}:@var{lower_bound1}-@var{upper_bound1}
+[:@var{lower_bound2}-@var{upper_bound2}...] tuples which sets
+the name of the counter and list of closed intervals.
+The @var{lower_bound} is optional and is zero
initialized if not set.
-All debug counters have the initial upper bound of @code{UINT_MAX};
-thus @code{dbg_cnt} returns true always unless the upper bound
-is set by this option.
-For example, with @option{-fdbg-cnt=dce:2:4,tail_call:10},
-@code{dbg_cnt(dce)} returns true only for third and fourth invocation.
+For example, with @option{-fdbg-cnt=dce:2-4:10-11,tail_call:10},
+@code{dbg_cnt(dce)} returns true only for second, third, fourth, tenth and
+eleventh invocation.
For @code{dbg_cnt(tail_call)} true is returned for first 10 invocations.
@item -print-file-name=@var{library}
more feature modifiers. This option has the form
@option{-march=@var{arch}@r{@{}+@r{[}no@r{]}@var{feature}@r{@}*}}.
-The permissible values for @var{arch} are @samp{armv8-a},
-@samp{armv8.1-a}, @samp{armv8.2-a}, @samp{armv8.3-a}, @samp{armv8.4-a},
-@samp{armv8.5-a} or @var{native}.
-
-The value @samp{armv8.5-a} implies @samp{armv8.4-a} and enables compiler
-support for the ARMv8.5-A architecture extensions.
-
-The value @samp{armv8.4-a} implies @samp{armv8.3-a} and enables compiler
-support for the ARMv8.4-A architecture extensions.
-
-The value @samp{armv8.3-a} implies @samp{armv8.2-a} and enables compiler
-support for the ARMv8.3-A architecture extensions.
-
-The value @samp{armv8.2-a} implies @samp{armv8.1-a} and enables compiler
-support for the ARMv8.2-A architecture extensions.
-
-The value @samp{armv8.1-a} implies @samp{armv8-a} and enables compiler
-support for the ARMv8.1-A architecture extension. In particular, it
-enables the @samp{+crc}, @samp{+lse}, and @samp{+rdma} features.
+The table below summarizes the permissible values for @var{arch}
+and the features that they enable by default:
+
+@multitable @columnfractions 0.20 0.20 0.60
+@headitem @var{arch} value @tab Architecture @tab Includes by default
+@item @samp{armv8-a} @tab Armv8-A @tab @samp{+fp}, @samp{+simd}
+@item @samp{armv8.1-a} @tab Armv8.1-A @tab @samp{armv8-a}, @samp{+crc}, @samp{+lse}, @samp{+rdma}
+@item @samp{armv8.2-a} @tab Armv8.2-A @tab @samp{armv8.1-a}
+@item @samp{armv8.3-a} @tab Armv8.3-A @tab @samp{armv8.2-a}
+@item @samp{armv8.4-a} @tab Armv8.4-A @tab @samp{armv8.3-a}, @samp{+fp16fml}, @samp{+dotprod}
+@item @samp{armv8.5-a} @tab Armv8.5-A @tab @samp{armv8.4-a}, @samp{+sb}, @samp{+ssbs}, @samp{+predres}
+@item @samp{armv8.6-a} @tab Armv8.6-A @tab @samp{armv8.5-a}, @samp{+bf16}, @samp{+i8mm}
+@end multitable
The value @samp{native} is available on native AArch64 GNU/Linux and
causes the compiler to pick the architecture of the host system. This
enable the extension at the assembler level and does not affect code
generation.
@item memtag
-Enable the Armv8.5-a Memory Tagging Extensions. This option is only to
-enable the extension at the assembler level and does not affect code
-generation.
+Enable the Armv8.5-a Memory Tagging Extensions.
+Use of this option with architectures prior to Armv8.5-A is not supported.
@item sb
Enable the Armv8-a Speculation Barrier instruction. This option is only to
enable the extension at the assembler level and does not affect code
Enable the Armv8-a Execution and Data Prediction Restriction instructions.
This option is only to enable the extension at the assembler level and does
not affect code generation. This option is enabled by default for
+@option{-march=armv8.5-a}.
@item sve2
Enable the Armv8-a Scalable Vector Extension 2. This also enables SVE
instructions.
Enable SVE2 aes instructions. This also enables SVE2 instructions.
@item sve2-sha3
Enable SVE2 sha3 instructions. This also enables SVE2 instructions.
-@option{-march=armv8.5-a}.
@item tme
Enable the Transactional Memory Extension.
+@item i8mm
+Enable 8-bit Integer Matrix Multiply instructions. This also enables
+Advanced SIMD and floating-point instructions. This option is enabled by
+default for @option{-march=armv8.6-a}. Use of this option with architectures
+prior to Armv8.2-A is not supported.
+@item bf16
+Enable brain half-precision floating-point instructions. This also enables
+Advanced SIMD and floating-point instructions. This option is enabled by
+default for @option{-march=armv8.6-a}. Use of this option with architectures
+prior to Armv8.2-A is not supported.
@end table
@opindex mea
Generate extended arithmetic instructions. Currently only
@code{divaw}, @code{adds}, @code{subs}, and @code{sat16} are
-supported. This is always enabled for @option{-mcpu=ARC700}.
+supported. Only valid for @option{-mcpu=ARC700}.
@item -mno-mpy
@opindex mno-mpy
Do not allow constant data to be placed in code sections.
Additionally, when compiling for ELF object format give all text sections the
ELF processor-specific section attribute @code{SHF_ARM_PURECODE}. This option
-is only available when generating non-pic code for M-profile targets with the
-MOVT instruction.
+is only available when generating non-pic code for M-profile targets.
@item -mcmse
@opindex mcmse
Functions prologues/epilogues are expanded as calls to appropriate
subroutines. Code size is smaller.
+@item -mdouble=@var{bits}
+@itemx -mlong-double=@var{bits}
+@opindex mdouble
+@opindex mlong-double
+Set the size (in bits) of the @code{double} or @code{long double} type,
+respectively. Possible values for @var{bits} are 32 an 64.
+Whether or not a specific value for @var{bits} is allowed depends on
+the @code{--with--double=} and @code{--with-long-double=}
+@w{@uref{https://gcc.gnu.org/install/configure.html#avr,configure options}},
+and the same applies for the default values of the options.
+
@item -mgas-isr-prologues
@opindex mgas-isr-prologues
Interrupt service routines (ISRs) may use the @code{__gcc_isr} pseudo
into GCC. However, an external @samp{devices.csv} file can be used to
extend device support beyond those that have been hard-coded.
-GCC searches for the @samp{devices.csv} file on the paths specified
-with the @code{-I} and @code{-L} options.
+GCC searches for the @samp{devices.csv} file using the following methods in the
+given precedence order, where the first method takes precendence over the
+second which takes precedence over the third.
+
+@table @asis
+@item Include path specified with @code{-I} and @code{-L}
+@samp{devices.csv} will be searched for in each of the directories specified by
+include paths and linker library search paths.
+@item Path specified by the environment variable @samp{MSP430_GCC_INCLUDE_DIR}
+Define the value of the global environment variable
+@samp{MSP430_GCC_INCLUDE_DIR}
+to the full path to the directory containing devices.csv, and GCC will search
+this directory for devices.csv. If devices.csv is found, this directory will
+also be registered as an include path, and linker library path. Header files
+and linker scripts in this directory can therefore be used without manually
+specifying @code{-I} and @code{-L} on the command line.
+@item The @samp{msp430-elf@{,bare@}/include/devices} directory
+Finally, GCC will examine @samp{msp430-elf@{,bare@}/include/devices} from the
+toolchain root directory. This directory does not exist in a default
+installation, but if the user has created it and copied @samp{devices.csv}
+there, then the MCU data will be read. As above, this directory will
+also be registered as an include path, and linker library path.
+
+@end table
+If none of the above search methods find @samp{devices.csv}, then the
+hard-coded MCU data is used.
+
@item -mwarn-mcu
@itemx -mno-warn-mcu
devices. The compiler includes special symbols in some objects
that tell the linker and runtime which code fragments are required.
+@item -mtiny-printf
+@opindex mtiny-printf
+Enable reduced code size @code{printf} and @code{puts} library functions.
+The @samp{tiny} implementations of these functions are not reentrant, so
+must be used with caution in multi-threaded applications.
+
+Support for streams has been removed and the string to be printed will
+always be sent to stdout via the @code{write} syscall. The string is not
+buffered before it is sent to write.
+
+This option requires Newlib Nano IO, so GCC must be configured with
+@samp{--enable-newlib-nano-formatted-io}.
+
@item -mcode-region=
@itemx -mdata-region=
@opindex mcode-region
CPUs based on AMD Family 15h cores with x86-64 instruction set support. (This
supersets FMA4, AVX, XOP, LWP, AES, PCLMUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A,
SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.)
+
@item bdver2
AMD Family 15h core based CPUs with x86-64 instruction set support. (This
supersets BMI, TBM, F16C, FMA, FMA4, AVX, XOP, LWP, AES, PCLMUL, CX16, MMX,
SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set
extensions.)
+
@item bdver3
AMD Family 15h core based CPUs with x86-64 instruction set support. (This
supersets BMI, TBM, F16C, FMA, FMA4, FSGSBASE, AVX, XOP, LWP, AES,
PCLMUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and
-64-bit instruction set extensions.
+64-bit instruction set extensions.)
+
@item bdver4
AMD Family 15h core based CPUs with x86-64 instruction set support. (This
supersets BMI, BMI2, TBM, F16C, FMA, FMA4, FSGSBASE, AVX, AVX2, XOP, LWP,
AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1,
-SSE4.2, ABM and 64-bit instruction set extensions.
+SSE4.2, ABM and 64-bit instruction set extensions.)
@item znver1
AMD Family 17h core based CPUs with x86-64 instruction set support. (This
supersets BMI, BMI2, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX,
SHA, CLZERO, AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3,
SSE4.1, SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, and 64-bit
-instruction set extensions.
+instruction set extensions.)
+
@item znver2
AMD Family 17h core based CPUs with x86-64 instruction set support. (This
-supersets BMI, BMI2, ,CLWB, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED,
+supersets BMI, BMI2, CLWB, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED,
MWAITX, SHA, CLZERO, AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A,
-SSSE3, SSE4.1, SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, and 64-bit
-instruction set extensions.)
-
+SSSE3, SSE4.1, SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, RDPID,
+WBNOINVD, and 64-bit instruction set extensions.)
@item btver1
CPUs based on AMD Family 14h cores with x86-64 instruction set support. (This
projects / thirdparty / gcc.git / blobdiff