@table @samp
@item make
she can still specify a different prefix from the one specified to
-@command{configure}, in which case, if needed, the package shall hard
+@command{configure}, in which case, if needed, the package should hard
code dependencies corresponding to the make-specified prefix.
@item make install
This is because @code{exit} predates @code{void}, and there was a long
tradition of it returning @code{int}.
-On more-modern hosts, the problem more likely is that @code{exit} is not
+On current hosts, the problem more likely is that @code{exit} is not
declared, due to C++ problems of some sort or another. For this reason
we suggest that test programs not invoke @code{exit}, but return from
@code{main} instead.
@c @fuindex vsprintf
@prindex @code{vsprintf}
The C standard says @code{sprintf} and @code{vsprintf} return the
-number of bytes written, but on some ancient systems (SunOS 4 for
-instance) they return the buffer pointer instead.
+number of bytes written. On some ancient systems (SunOS 4 for
+instance) they return the buffer pointer instead, but these no
+longer need to be worried about.
@item @code{sscanf}
@c @fuindex sscanf
Currently this test is implemented by running a test program. When
cross compiling the pessimistic assumption that @code{closedir} does not
return a meaningful value is made.
+
+This macro is obsolescent, as @code{closedir} returns a meaningful value
+on current systems. New programs need not use this macro.
@end defmac
@defmac AC_FUNC_ERROR_AT_LINE
@code{NLIST_NAME_UNION} is still defined, but do not depend upon it.
@item
-Programs may need to be installed setgid (or setuid) for
+Programs may need to be installed set-group-ID (or set-user-ID) for
@code{getloadavg} to work. In this case, define
@code{GETLOADAVG_PRIVILEGED}, set the output variable @code{NEED_SETGID}
to @samp{true} (and otherwise to @samp{false}), and set
This macro does not check whether
@code{getpgrp} exists at all; if you need to work in that situation,
first call @code{AC_CHECK_FUNC} for @code{getpgrp}.
+
+This macro is obsolescent, as current systems have a @code{getpgrp}
+whose signature conforms to Posix. New programs need not use this macro.
@end defmac
@defmac AC_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK
bytes or more and with at least one buffer not starting on a 4-byte
boundary (such as the one on NeXT x86 OpenStep), require an
@code{AC_LIBOBJ} replacement for @samp{memcmp}.
+
+This macro is obsolescent, as current systems have a working
+@code{memcmp}. New programs need not use this macro.
@end defmac
@defmac AC_FUNC_MBRTOWC
@c @fuindex mmap
@prindex @code{mmap}
If the @code{mmap} function exists and works correctly, define
-@code{HAVE_MMAP}. Only checks private fixed mapping of already-mapped
+@code{HAVE_MMAP}. This checks only private fixed mapping of already-mapped
memory.
@end defmac
@code{SELECT_TYPE_ARG5} respectively. @code{SELECT_TYPE_ARG1} defaults
to @samp{int}, @code{SELECT_TYPE_ARG234} defaults to @samp{int *},
and @code{SELECT_TYPE_ARG5} defaults to @samp{struct timeval *}.
+
+This macro is obsolescent, as current systems have a @code{select} whose
+signature conforms to Posix. New programs need not use this macro.
@end defmac
@defmac AC_FUNC_SETPGRP
two process IDs as arguments. This macro does not check whether
@code{setpgrp} exists at all; if you need to work in that situation,
first call @code{AC_CHECK_FUNC} for @code{setpgrp}.
+
+This macro is obsolescent, as current systems have a @code{setpgrp}
+whose signature conforms to Posix. New programs need not use this macro.
@end defmac
@defmac AC_FUNC_STAT
If it does, then define @code{HAVE_STAT_EMPTY_STRING_BUG} (or
@code{HAVE_LSTAT_EMPTY_STRING_BUG}) and ask for an @code{AC_LIBOBJ}
replacement of it.
+
+These macros are obsolescent, as no current systems have the bug.
+New programs need not use these macros.
@end defmac
@defmac AC_FUNC_SETVBUF_REVERSED
If @code{setvbuf} takes the buffering type as its second argument and
the buffer pointer as the third, instead of the other way around, define
@code{SETVBUF_REVERSED}.
+
+This macro is obsolescent, as no current systems have the bug.
+New programs need not use this macro.
@end defmac
@defmac AC_FUNC_STRCOLL
@prindex @code{strftime}
Check for @code{strftime} in the @file{intl} library, for SCO Unix.
Then, if @code{strftime} is available, define @code{HAVE_STRFTIME}.
+
+This macro is obsolescent, as no current systems require the @file{intl}
+library for @code{strftime}. New programs need not use this macro.
@end defmac
@defmac AC_FUNC_STRTOD
@prindex @code{strnlen}
If the @code{strnlen} function is not available, or is buggy (like the one
from @acronym{AIX} 4.3), require an @code{AC_LIBOBJ} replacement for it.
+
+This macro is obsolescent, as no current systems have the bug.
+New programs need not use this macro.
@end defmac
@defmac AC_FUNC_UTIME_NULL
@prindex @code{utime}
If @samp{utime (@var{file}, NULL)} sets @var{file}'s timestamp to
the present, define @code{HAVE_UTIME_NULL}.
+
+This macro is obsolescent, as all current systems have a @code{utime}
+that behaves this way. New programs need not use this macro.
@end defmac
@defmac AC_FUNC_VPRINTF
@code{_doprnt} is found, define @code{HAVE_DOPRNT}. (If @code{vprintf}
is available, you may assume that @code{vfprintf} and @code{vsprintf}
are also available.)
+
+This macro is obsolescent, as all current systems have @code{vprintf}.
+New programs need not use this macro.
@end defmac
@defmac AC_REPLACE_FNMATCH
This macro also checks for the SCO Xenix @file{dir} and @file{x} libraries.
+This macro is obsolescent, as all current systems with directory
+libraries have @code{<dirent.h>}. New programs need not use this macro.
+
Also see @code{AC_STRUCT_DIRENT_D_INO} and
@code{AC_STRUCT_DIRENT_D_TYPE} (@pxref{Particular Structures}).
@end defmac
@file{sys/stat.h} do not work properly (returning false positives),
define @code{STAT_MACROS_BROKEN}. This is the case on Tektronix UTekV,
Amdahl UTS and Motorola System V/88.
+
+This macro is obsolescent, as no current systems have the bug.
+New programs need not use this macro.
@end defmac
@defmac AC_HEADER_STDBOOL
functions), and whether the @file{ctype.h} macros work on characters
with the high bit set, as the C standard requires.
-Nowadays this macro is becoming obsolete. However, if you use it, your
-code can refer to @code{STDC_HEADERS} instead of @code{__STDC__} to
+If you use this macro, your code can refer to @code{STDC_HEADERS} to
determine whether the system has conforming header files (and probably C
-library functions). This is useful if you worry about portability
-to ancient systems that lack C89 header files.
+library functions).
+
+This macro is obsolescent, as current systems have conforming header
+files. New programs need not use this macro.
@hdrindex{string.h}
@hdrindex{strings.h}
@code{strcpy}, and @file{strings.h} is standardized by Posix and declares
@acronym{BSD} functions like @code{bcopy}; but
historically, string functions were a major sticking point in this area.
-If you worry about portability to ancient systems without standard
-headers, there is so much variation
+If you still want to worry about portability to ancient systems without
+standard headers, there is so much variation
that it is probably easier to declare the functions you use than to
figure out exactly what the system header files declare. Some ancient systems
-contain a mix of functions from the C standard and from @acronym{BSD}; some are
-mostly standard but lack @samp{memmove}; some define the
+contained a mix of functions from the C standard and from @acronym{BSD};
+some were mostly standard but lacked @samp{memmove}; some defined the
@acronym{BSD} functions as macros in @file{string.h} or
-@file{strings.h}; some have only the @acronym{BSD} functions but
-@file{string.h}; some declare the memory functions in @file{memory.h},
+@file{strings.h}; some had only the @acronym{BSD} functions but
+@file{string.h}; some declared the memory functions in @file{memory.h},
some in @file{string.h}; etc. It is probably sufficient to check for
-one string function and one memory function; if the library has the
-standard versions of those then it probably has most of the others.
+one string function and one memory function; if the library had the
+standard versions of those then it probably had most of the others.
If you put the following in @file{configure.ac}:
@example
+# This example is obsolescent.
+# Nowadays you can omit these macro calls.
AC_HEADER_STDC
AC_CHECK_FUNCS([strchr memcpy])
@end example
@example
@group
+/* This example is obsolescent.
+ Nowadays you can just #include <string.h>. */
#if STDC_HEADERS
# include <string.h>
#else
@noindent
If you use a function like @code{memchr}, @code{memset}, @code{strtok},
or @code{strspn}, which have no @acronym{BSD} equivalent, then macros won't
-suffice; you must provide an implementation of each function. An easy
+suffice to port to ancient hosts; you must provide an implementation of
+each function. An easy
way to incorporate your implementations only when needed (since the ones
in system C libraries may be hand optimized) is to, taking @code{memchr}
for example, put it in @file{memchr.c} and use
#endif
@end group
@end example
+
+@noindent
+This macro is obsolescent, as current systems are compatible with Posix.
+New programs need not use this macro.
@end defmac
@cvindex _POSIX_VERSION
@hdrindex{time.h}
@hdrindex{sys/time.h}
If a program may include both @file{time.h} and @file{sys/time.h},
-define @code{TIME_WITH_SYS_TIME}. On some older systems,
-@file{sys/time.h} includes @file{time.h}, but @file{time.h} is not
-protected against multiple inclusion, so programs should not explicitly
+define @code{TIME_WITH_SYS_TIME}. On some ancient systems,
+@file{sys/time.h} included @file{time.h}, but @file{time.h} was not
+protected against multiple inclusion, so programs could not explicitly
include both files. This macro is useful in programs that use, for
example, @code{struct timeval} as well as
@code{struct tm}. It is best used in conjunction with
#endif
@end group
@end example
+
+@noindent
+This macro is obsolescent, as current systems can include both files
+when they exist. New programs need not use this macro.
@end defmac
@code{HAVE_STRUCT_DIRENT_D_INO} indicates only the presence of
@code{d_ino}, not whether its contents are always reliable.
Traditionally, a zero @code{d_ino} indicated a deleted directory entry,
-though modern systems hide this detail from the user and never return
+though current systems hide this detail from the user and never return
zero @code{d_ino} values.
+Many current systems report an incorrect @code{d_ino} for a directory
+entry that is a mount point.
@end defmac
@defmac AC_STRUCT_DIRENT_D_TYPE
If @file{time.h} does not define @code{struct tm}, define
@code{TM_IN_SYS_TIME}, which means that including @file{sys/time.h}
had better define @code{struct tm}.
+
+This macro is obsolescent, as @file{time.h} defines @code{struct tm} in
+current systems. New programs need not use this macro.
@end defmac
@defmac AC_STRUCT_TIMEZONE
@acindex{HAVE_C_BACKSLASH_A}
Define @samp{HAVE_C_BACKSLASH_A} to 1 if the C compiler understands
@samp{\a}.
+
+This macro is obsolescent, as current C compilers understand @samp{\a}.
+New programs need not use this macro.
@end defmac
@defmac AC_C_BIGENDIAN (@ovar{action-if-true}, @ovar{action-if-false}, @ovar{action-if-unknown})
C++ compiler to compile C code is not recommended or supported, and
installers who run into trouble in this area should get a C compiler
like GCC to compile their C code.
+
+This macro is obsolescent, as current C compilers support @code{const}.
+New programs need not use this macro.
@end defmac
@defmac AC_C_RESTRICT
you might expect that @code{volatile} is available only when
@code{__STDC__} is defined. However, Ultrix 4.3's native compiler does
support volatile, but does not define @code{__STDC__}.
+
+This macro is obsolescent, as current C compilers support @code{volatile}.
+New programs need not use this macro.
@end defmac
@defmac AC_C_INLINE
@example
#define x(y) #y
@end example
+
+This macro is obsolescent, as current C compilers support the
+stringizing operator. New programs need not use this macro.
@end defmac
@defmac AC_C_TYPEOF
@code{AC_PROG_CC}), define @code{PROTOTYPES} and @code{__PROTOTYPES}.
Defining @code{__PROTOTYPES} is for the benefit of
header files that cannot use macros that infringe on user name space.
+
+This macro is obsolescent, as current C compilers support prototypes.
+New programs need not use this macro.
@end defmac
@defmac AC_PROG_GCC_TRADITIONAL
Add @option{-traditional} to output variable @code{CC} if using the
@acronym{GNU} C compiler and @code{ioctl} does not work properly without
@option{-traditional}. That usually happens when the fixed header files
-have not been installed on an old system. Since recent versions of the
-@acronym{GNU} C compiler fix the header files automatically when installed,
-this macro is becoming obsolete.
+have not been installed on an old system.
+
+This macro is obsolescent, since current versions of the @acronym{GNU} C
+compiler fix the header files automatically when installed.
@end defmac
@group
# Checks for programs.
AC_PROG_CC
-AC_PROG_GCC_TRADITIONAL
+AC_PROG_AWK
@r{ @dots{} more program checks @dots{}}
AC_CACHE_SAVE
@end group
After the category comes the name of the particular feature being
tested. Any further words in the macro name indicate particular aspects
-of the feature. For example, @code{AC_FUNC_UTIME_NULL} checks the
-behavior of the @code{utime} function when called with a @code{NULL}
-pointer.
+of the feature. For example, @code{AC_FUNC_FNMATCH_GNU} checks whether
+the @code{fnmatch} function supports @acronym{GNU} extensions.
An internal macro should have a name that starts with an underscore;
Autoconf internals should therefore start with @samp{_AC_}.
shells; restrict yourself to the lowest common denominator. Even
@code{unset} is not supported by all shells!
-Some old systems have quite
+Some ancient systems have quite
small limits on the length of the @samp{#!} line; for instance, 32
bytes (not including the newline) on SunOS 4.
A few ancient 4.2@acronym{BSD} based systems (such as Dynix circa 1984)
-required a single space between the @samp{#!} and the @samp{/}, but
-these are no longer of practical concern.
+required a single space between the @samp{#!} and the @samp{/}.
+However, these ancient systems are no longer of practical concern.
The set of external programs you should run in a @command{configure} script
is fairly small. @xref{Utilities in Makefiles, , Utilities in
@cindex File descriptors
@cindex Shell file descriptors
-Some file descriptors shall not be used, since some systems, admittedly
-arcane, use them for special purpose:
-
-@display
-3 --- some systems may open it to @samp{/dev/tty}.
-4 --- used on the Kubota Titan.
-@end display
-
Don't redirect the same file descriptor several times, as you are doomed
to failure under Ultrix.
Don't try to move/delete open files, such as in @samp{exec >foo; mv foo
bar}; see @ref{Limitations of Builtins}, @command{mv} for more details.
+Don't rely on file descriptors 0, 1, and 2 remaining closed in a
+subsidiary program. If any of these descriptors is closed, the
+operating system may open an unspecified file for the descriptor in the
+new process image. Posix says this may be done only if the subsidiary
+program is set-user-ID or set-group-ID, but HP-UX 11.23 does it even for
+ordinary programs.
+
Don't rely on open file descriptors being open in child processes. In
@command{ksh}, file descriptors above 2 which are opened using
-@samp{exec n>file} are closed by a subsequent @samp{exec} (such as
+@samp{exec @var{n}>file} are closed by a subsequent @samp{exec} (such as
that involved in the fork-and-exec which runs a program or script).
-Thus, using sh, we have:
+Thus, using @command{sh}, we have:
@example
$ @kbd{cat ./descrips}
@noindent
Within the process which runs the @samp{descrips} script, file
-descriptor number 5 is closed.
+descriptor 5 is closed.
+
+A few ancient systems reserved some file descriptors. By convention,
+file descriptor 3 was opened to @file{/dev/tty} when you logged into
+Eighth Edition (1985) through Tenth Edition Unix (1989). File
+descriptor 4 had a special use on the Stardent/Kubota Titan (circa
+1990), though we don't now remember what it was. Both these systems are
+obsolete, so it's now safe to treat file descriptors 3 and 4 like any
+other file descriptors.
@node File System Conventions
@section File System Conventions
@item LINENO
Most modern shells provide the current line number in @code{LINENO}.
Its value is the line number of the beginning of the current command.
-Autoconf attempts to execute @command{configure} with a modern shell.
+Autoconf attempts to execute @command{configure} with a shell that
+supports @code{LINENO}.
If no such shell is available, it attempts to implement @code{LINENO}
with a Sed prepass that replaces each instance of the string
@code{$LINENO} (not followed by an alphanumeric character) with the
@prindex @command{!}
The Unix version 7 shell did not support
negating the exit status of commands with @command{!}, and this feature
-is still absent from more modern shells (e.g., Solaris @command{/bin/sh}).
+is still absent from some shells (e.g., Solaris @command{/bin/sh}).
Shell code like this:
@example
@item @command{cp}
@c ---------------
@prindex @command{cp}
-Avoid the @option{-r} option, since its behavior is not specified by
-Posix. Use @option{-R} instead. On @acronym{GNU} hosts the two options
+Avoid the @option{-r} option, since Posix 1003.1-2004 marks it as
+obsolescent and its behavior on special files is implementation-defined.
+Use @option{-R} instead. On @acronym{GNU} hosts the two options
are equivalent, but on Solaris hosts (for example) @command{cp -r}
reads from pipes instead of replicating them.
/tmp/newdir/} if @file{/tmp/newdir} does not exist.
@c This is thanks to Ian.
-SunOS 4 @command{cp} does not support @option{-f}, although its
-@command{mv} does. It's possible to deduce why @command{mv} and
-@command{cp} are different with respect to @option{-f}. @command{mv}
-prompts by default before overwriting a read-only file. @command{cp}
-does not. Therefore, @command{mv} requires a @option{-f} option, but
-@command{cp} does not. @command{mv} and @command{cp} behave differently
-with respect to read-only files because the simplest form of
-@command{cp} cannot overwrite a read-only file, but the simplest form of
-@command{mv} can. This is because @command{cp} opens the target for
-write access, whereas @command{mv} simply calls @code{link} (or, in
-newer systems, @code{rename}).
-@c Ian said: ``I don't think -p or -r are portable''!!! How can you live
-@c without -r???
+The ancient SunOS 4 @command{cp} does not support @option{-f}, although
+its @command{mv} does.
@cindex timestamp resolution
Traditionally, file timestamps had 1-second resolution, and @samp{cp
Unfortunately this behaves exactly as the original expression; see the
@samp{@command{expr} (@samp{|})} entry for more information.
-Older @command{expr} implementations (e.g., SunOS 4 @command{expr} and
+Ancient @command{expr} implementations (e.g., SunOS 4 @command{expr} and
Solaris 8 @command{/usr/ucb/expr}) have a silly length limit that causes
@command{expr} to fail if the matched substring is longer than 120
bytes. In this case, you might want to fall back on @samp{echo|sed} if
-@command{expr} fails.
+@command{expr} fails. Nowadays this is of practical importance only for
+the rare installer who mistakenly puts @file{/usr/ucb} before
+@file{/usr/bin} in @env{PATH}.
On Mac OS X 10.4, @command{expr} mishandles the pattern @samp{[^-]} in
some cases. For example, the command
@c ---------------
@prindex @command{ls}
@cindex Listing directories
-The portable options are @option{-acdilrtu}. Modern practice is for
-@option{-l} to output both owner and group, but traditional
-@command{ls} omits the group.
-
-@c From Bruce Lilly:
-@c
-@c # telnet dim
-@c [...]
-@c Unix System V (TWG-TCP/IP) (dim.blilly.com)
-@c [...]
-@c $ mkdir foo
-@c $ cd foo
-@c $ /bin/ls a.exe 2>/dev/null
-@c a.exe not found
-@c $ what /bin/ls
-@c /bin/ls:
-@c fndcmd:fndcmd.sl 1.68
-@c $ uname -a
-@c Unix dim SYSTEM5 3.51m mc68k
-@c
-@c It's an AT&T 3B1. See http://www.faqs.org/faqs/3b1-faq/ or any
-@c mirror of the 3B1 FAQ. It's actually SVR2.2.
-Modern practice is for all diagnostics to go to standard error, but
-traditional @samp{ls foo} prints the message @samp{foo not found} to
-standard output if @file{foo} does not exist. Be careful when writing
-shell commands like @samp{sources=`ls *.c 2>/dev/null`}, since with
-traditional @command{ls} this is equivalent to @samp{sources="*.c not
-found"} if there are no @samp{.c} files.
+The portable options are @option{-acdilrtu}. Current practice is for
+@option{-l} to output both owner and group, even though ancient versions
+of @command{ls} omitted the group.
+On ancient hosts, @samp{ls foo} sent the diagnostic @samp{foo not found}
+to standard output if @file{foo} did not exist. Hence a shell command
+like @samp{sources=`ls *.c 2>/dev/null`} did not always work, since it
+was equivalent to @samp{sources='*.c not found'} in the absence of
+@samp{.c} files. This is no longer a practical problem, since current
+@command{ls} implementations send diagnostics to standard error.
@item @command{mkdir}
@c ------------------
Anchors (@samp{^} and @samp{$}) inside groups are not portable.
Nested parenthesization in patterns (e.g., @samp{\(\(a*\)b*)\)}) is
-quite portable to modern hosts, but is not supported by some older
+quite portable to current hosts, but was not supported by some ancient
@command{sed} implementations like SVR3.
Some @command{sed} implementations, e.g., Solaris,
@code{utimes} system call, which can result in the same kind of
timestamp truncation problems that @samp{cp -p} has.
-On some old @acronym{BSD} systems, @command{touch} or any command that
+On ancient @acronym{BSD} systems, @command{touch} or any command that
results in an empty file does not update the timestamps, so use a
command like @command{echo} as a workaround.
-
+Also,
@acronym{GNU} @command{touch} 3.16r (and presumably all before that)
fails to work on SunOS 4.1.3 when the empty file is on an
@acronym{NFS}-mounted 4.2 volume.
+However, these problems are no longer of practical concern.
@end table
@cindex @code{VPATH} and double-colon rules
@cindex double-colon rules and @code{VPATH}
-Any assignment to @code{VPATH} causes Sun @command{make} to only execute
-the first set of double-colon rules. (This comment has been here since
-1994 and the context has been lost. It's probably about SunOS 4. If
-you can reproduce this, please send us a test case for illustration.)
+With ancient versions of Sun @command{make},
+any assignment to @code{VPATH} @command{make} to only execute
+the first set of double-colon rules.
+However, this problem is no longer of practical concern.
@item @code{$<} not supported in explicit rules
@cindex explicit rules, @code{$<}, and @code{VPATH}
@cindex @code{VPATH} and automatic rule rewriting
@cindex automatic rule rewriting and @code{VPATH}
-Some @command{make} implementations, such as SunOS 4 @command{make} or
-OSF1/Tru64 @command{make}, will search prerequisites in @code{VPATH} and
-rewrite all their occurrences in the rule appropriately.
-
-For instance
+Some @command{make} implementations, such as Solaris @command{make} and
+OSF1/Tru64 @command{make}, search for prerequisites in @code{VPATH} and
+then rewrite each occurrence as a plain word in the rule.
+For instance:
@example
+# This isn't portable to GNU make.
VPATH = ../pkg/src
f.c: if.c
cp if.c f.c
@end example
@noindent
-would execute @code{cp ../pkg/src/if.c f.c} if @file{if.c} was
-found in @file{../pkg/src}. That sounds great.
+executes @code{cp ../pkg/src/if.c f.c} if @file{if.c} is
+found in @file{../pkg/src}.
-However, for the sake of other @command{make} implementations, we can't
-rely on this, and we have to search @code{VPATH} manually:
+However, portable makefiles cannot rely on this behavior, and should
+search @code{VPATH} manually. It is tempting to write this:
@smallexample
+# This isn't portable to Solaris make.
VPATH = ../pkg/src
f.c: if.c
cp `test -f if.c || echo $(VPATH)/`if.c f.c
@end smallexample
@noindent
-However the "prerequisite rewriting" still applies here. So if
-@file{if.c} is in @file{../pkg/src}, SunOS 4 @command{make} and OSF1/Tru64
+However the ``prerequisite rewriting'' still applies here. So if
+@file{if.c} is in @file{../pkg/src}, Solaris @command{make} and OSF1/Tru64
@command{make} will execute
@smallexample
@noindent
and thus fails. Oops.
-One workaround is to make sure that @file{if.c} never appears as a plain word
-in the rule. For instance these three rules would be safe.
+A simple workaround, and good practice anyway, is to use @samp{$?} and
+@samp{$@@} when possible:
@smallexample
VPATH = ../pkg/src
f.c: if.c
- cp `test -f ./if.c || echo $(VPATH)/`if.c f.c
-g.c: ig.c
- cp `test -f 'ig.c' || echo $(VPATH)/`ig.c g.c
-h.c: ih.c
- cp `test -f "ih.c" || echo $(VPATH)/`ih.c h.c
+ cp $? $@@
+@end smallexample
+
+@noindent
+but this does not generalize well to commands with multiple
+prerequisites. A more general workaround is to rewrite the rule so that
+the prerequisite @file{if.c} never appears as a plain word. For
+example, these three rules would be safe, assuming @file{if.c} is in
+@file{../pkg/src} and the other files are in the working directory:
+
+@smallexample
+VPATH = ../pkg/src
+f.c: if.c f1.c
+ cat `test -f ./if.c || echo $(VPATH)/`if.c f1.c >$@@
+g.c: if.c g1.c
+ cat `test -f 'if.c' || echo $(VPATH)/`if.c g1.c >$@@
+h.c: if.c h1.c
+ cat `test -f "if.c" || echo $(VPATH)/`if.c h1.c >$@@
@end smallexample
Things get worse when your prerequisites are in a macro.
done
@end example
-The above @code{install-HEADERS} rule is not SunOS-4-proof because @code{for
+The above @code{install-HEADERS} rule is not Solaris-proof because @code{for
i in $(HEADERS);} will be expanded as @code{for i in f.h g.h h.h;}
where @code{f.h} and @code{g.h} are plain words and are hence
subject to @code{VPATH} adjustments.
@c LocalWords: PowerPC GNUC libPW pragma Olibcalls CHOWN chown CLOSEDIR VFORK
@c LocalWords: closedir FNMATCH fnmatch vfork FSEEKO LARGEFILE fseeko SVR sc
@c LocalWords: largefile GETGROUPS getgroups GETLOADAVG DGUX UMAX NLIST KMEM
-@c LocalWords: GETLODAVG SETGID getloadavg nlist setgid setuid GETMNTENT irix
+@c LocalWords: GETLODAVG SETGID getloadavg nlist GETMNTENT irix
@c LocalWords: getmntent UnixWare GETPGRP getpgid getpgrp Posix's pid LSTAT
@c LocalWords: lstat rpl MEMCMP memcmp OpenStep MBRTOWC mbrtowc MKTIME mktime
@c LocalWords: localtime MMAP mmap OBSTACK obstack obstacks ARGTYPES timeval
@c LocalWords: VER Gnulib online xyes strcpy TYPEOF typeof OBJC objcc objc ln
@c LocalWords: GOBJC OBJCCPP OTP ERLC erl valloc decr dumpdef errprint incr
@c LocalWords: esyscmd len maketemp pushdef substr syscmd sysval translit txt
-@c LocalWords: sinclude foreach myvar tolower toupper uniq BASENAME STDIN ig
-@c LocalWords: Dynix descrips basename aname cname ih macroexpands xno xcheck
+@c LocalWords: sinclude foreach myvar tolower toupper uniq BASENAME STDIN
+@c LocalWords: Dynix descrips basename aname cname macroexpands xno xcheck
@c LocalWords: LIBREADLINE lreadline lncurses libreadline
@c Local Variables:
projects / thirdparty / autoconf.git / commitdiff
