@end tex
Pinard, Karl Berry, Richard Pixley, Ian Lance Taylor, Roland McGrath,
and Noah Friedman. It was inspired by Brian Fox's automatic
-configuration system for BASH, by Larry Wall's Metaconfig, and by
+configuration system for Bash, by Larry Wall's Metaconfig, and by
Richard Stallman, Richard Pixley, and John Gilmore's configuration tools
for the GNU compiler and object file utilities.
@display
@group
@code{AC_INIT(@var{file})}
-checks for programs
-checks for UNIX variants that set @code{DEFS}
+checks for alternative programs
+checks for UNIX variants that set C preprocessor variables
checks for header files
checks for typedefs
-checks for functions
-checks for structure members
+checks for library functions
+checks for structures
checks for compiler characteristics
-checks for operating system services
+checks for system services
other checks for UNIX variants
@code{AC_OUTPUT(@r{[}@var{file@dots{}}@r{]})}
@end group
the standard output.
The Autoconf macros are defined in two or more files. Two of the files
-are distributed with Autoconf: @file{acgeneral.m4} (@pxref{General
-Purpose Macros}) and @file{acspecific.m4} (@pxref{Specific Tests}).
-@code{autoconf} also looks for an optional file called @file{aclocal.m4}
-both in the directory that contains other installed Autoconf macro files and
-in the current directory. (If both files exist, it uses both of them.)
-Those files can contain your site's own locally written Autoconf macro
-definitions. @xref{Writing Macros}, for more information.
+are distributed with Autoconf: @code{autoconf} first reads
+@file{acgeneral.m4} (@pxref{General Purpose Macros}), then
+@file{acspecific.m4} (@pxref{Specific Tests}). After reading them,
+@code{autoconf} looks for an optional file called @file{aclocal.m4},
+first in the directory that contains other installed Autoconf macro
+files, and then in the current directory. If both files exist, it uses
+both of them. Those files can contain your site's own locally written
+Autoconf macro definitions (@pxref{Writing Macros}, for more
+information). If a macro is defined in more than one of the files that
+@code{autoconf} reads, the last definition it reads overrides the
+earlier ones.
You can override the directory where @code{autoconf} looks for the
installed macro files by setting the @code{AC_MACRODIR} environment
@code{autoheader} scans @file{configure.in} and figures out which C
preprocessor symbols it might define. It copies comments and
@code{#define} and @code{#undef} statements from a file called
-@file{acconfig.h}, which comes with and is installed with Autoconf; it
+@file{acconfig.h}, which comes with and is installed with Autoconf. It
also uses a file called @file{acconfig.h} in the current directory, if
-present. For symbols that @code{AC_HAVE_HEADERS} or
+present; you must create that file to contain entries for symbols that
+you @code{AC_DEFINE}. For symbols that @code{AC_HAVE_HEADERS} or
@code{AC_HAVE_FUNCS} define, @code{autoheader} generates comments and
@code{#undef} statements itself rather than copying them from a file,
since the possible symbols are effectively limitless.
Many of the specific test macros use the value of @code{CPP} indirectly
by calling @code{AC_TEST_CPP}, @code{AC_HEADER_CHECK},
@code{AC_HEADER_EGREP}, or @code{AC_PROGRAM_EGREP}. Those macros call
-this macro first if it hasn't been called already. It should be called
-after @code{AC_PROG_CC}.
+this macro first if it hasn't been called already. It calls
+@code{AC_PROG_CC} if it hasn't been called already.
@end defmac
@defmac AC_PROG_LEX
@file{sys/dir.h}, define @code{SYSDIR}; otherwise, if it has
@file{ndir.h}, define @code{NDIR}. Also, if the directory library
header file contains a declaration of the @code{closedir} function with
-a @code{void} return type, define @code{VOID_CLOSEDIR}. The directory
-library declarations in the source code should look something like the
-following:
+a @code{void} return type, define @code{VOID_CLOSEDIR}.
+
+The directory library declarations in the source code should look
+something like the following, which assumes that you have also called
+@samp{AC_HAVE_HEADERS(unistd.h)}:
@example
@group
+#ifdef HAVE_UNISTD_H
+#include <sys/types.h>
+#include <unistd.h>
+#endif
+
/* unistd.h defines _POSIX_VERSION on POSIX.1 systems. */
#if defined(DIRENT) || defined(_POSIX_VERSION)
#include <dirent.h>
@defmac AC_UNISTD_H
@maindex UNISTD_H
@vindex HAVE_UNISTD_H
-Define @code{HAVE_UNISTD_H} if the system has @file{unistd.h}. The way
-to check if the system supports POSIX.1 is:
+Define @code{HAVE_UNISTD_H} if the system has @file{unistd.h}. This
+macro is obsolete; instead, use @samp{AC_HAVE_HEADERS(unistd.h)}.
+
+The way to check if the system supports POSIX.1 is:
@example
@group
(so programs can periodically call @samp{alloca(0)} to garbage collect).
This variable is separate from @code{LIBOBJS} so multiple programs can
share the value of @code{ALLOCA} without needing to create an actual
-library.
+library, in case only some of them use the code in @code{LIBOBJS}.
If this macro finds @file{alloca.h}, it defines @code{HAVE_ALLOCA_H}.
@var{action-if-not-found}.
You can not check whether preprocessor symbols are defined this way,
-because they get expanded before @code{egrep} sees them. You can
-probably just put @code{#ifdef} directives in your C programs to detect
-them, but if you want to do the check in @code{configure} for some
-reason (perhaps to determine which of several files to include), then
-use @code{AC_PROGRAM_EGREP}, like this:
-
-@example
-AC_PROGRAM_EGREP(yes, [#include <stdio.h>
-#ifdef P_tmpdir
-yes
-#endif
-], AC_DEFINE(HAVE_P_TMPDIR))
-@end example
+because they get expanded before @code{egrep} sees them. But you can
+almost always detect them by simply using @code{#ifdef} directives in
+your C programs.
@end defmac
@defmac AC_PREFIX (@var{program})
@example
prefix = /usr/local
-exec_prefix = ${prefix}
+exec_prefix = $@{prefix@}
@end example
@noindent
@end tex
Pinard, Karl Berry, Richard Pixley, Ian Lance Taylor, Roland McGrath,
and Noah Friedman. It was inspired by Brian Fox's automatic
-configuration system for BASH, by Larry Wall's Metaconfig, and by
+configuration system for Bash, by Larry Wall's Metaconfig, and by
Richard Stallman, Richard Pixley, and John Gilmore's configuration tools
for the GNU compiler and object file utilities.
@display
@group
@code{AC_INIT(@var{file})}
-checks for programs
-checks for UNIX variants that set @code{DEFS}
+checks for alternative programs
+checks for UNIX variants that set C preprocessor variables
checks for header files
checks for typedefs
-checks for functions
-checks for structure members
+checks for library functions
+checks for structures
checks for compiler characteristics
-checks for operating system services
+checks for system services
other checks for UNIX variants
@code{AC_OUTPUT(@r{[}@var{file@dots{}}@r{]})}
@end group
the standard output.
The Autoconf macros are defined in two or more files. Two of the files
-are distributed with Autoconf: @file{acgeneral.m4} (@pxref{General
-Purpose Macros}) and @file{acspecific.m4} (@pxref{Specific Tests}).
-@code{autoconf} also looks for an optional file called @file{aclocal.m4}
-both in the directory that contains other installed Autoconf macro files and
-in the current directory. (If both files exist, it uses both of them.)
-Those files can contain your site's own locally written Autoconf macro
-definitions. @xref{Writing Macros}, for more information.
+are distributed with Autoconf: @code{autoconf} first reads
+@file{acgeneral.m4} (@pxref{General Purpose Macros}), then
+@file{acspecific.m4} (@pxref{Specific Tests}). After reading them,
+@code{autoconf} looks for an optional file called @file{aclocal.m4},
+first in the directory that contains other installed Autoconf macro
+files, and then in the current directory. If both files exist, it uses
+both of them. Those files can contain your site's own locally written
+Autoconf macro definitions (@pxref{Writing Macros}, for more
+information). If a macro is defined in more than one of the files that
+@code{autoconf} reads, the last definition it reads overrides the
+earlier ones.
You can override the directory where @code{autoconf} looks for the
installed macro files by setting the @code{AC_MACRODIR} environment
@code{autoheader} scans @file{configure.in} and figures out which C
preprocessor symbols it might define. It copies comments and
@code{#define} and @code{#undef} statements from a file called
-@file{acconfig.h}, which comes with and is installed with Autoconf; it
+@file{acconfig.h}, which comes with and is installed with Autoconf. It
also uses a file called @file{acconfig.h} in the current directory, if
-present. For symbols that @code{AC_HAVE_HEADERS} or
+present; you must create that file to contain entries for symbols that
+you @code{AC_DEFINE}. For symbols that @code{AC_HAVE_HEADERS} or
@code{AC_HAVE_FUNCS} define, @code{autoheader} generates comments and
@code{#undef} statements itself rather than copying them from a file,
since the possible symbols are effectively limitless.
Many of the specific test macros use the value of @code{CPP} indirectly
by calling @code{AC_TEST_CPP}, @code{AC_HEADER_CHECK},
@code{AC_HEADER_EGREP}, or @code{AC_PROGRAM_EGREP}. Those macros call
-this macro first if it hasn't been called already. It should be called
-after @code{AC_PROG_CC}.
+this macro first if it hasn't been called already. It calls
+@code{AC_PROG_CC} if it hasn't been called already.
@end defmac
@defmac AC_PROG_LEX
@file{sys/dir.h}, define @code{SYSDIR}; otherwise, if it has
@file{ndir.h}, define @code{NDIR}. Also, if the directory library
header file contains a declaration of the @code{closedir} function with
-a @code{void} return type, define @code{VOID_CLOSEDIR}. The directory
-library declarations in the source code should look something like the
-following:
+a @code{void} return type, define @code{VOID_CLOSEDIR}.
+
+The directory library declarations in the source code should look
+something like the following, which assumes that you have also called
+@samp{AC_HAVE_HEADERS(unistd.h)}:
@example
@group
+#ifdef HAVE_UNISTD_H
+#include <sys/types.h>
+#include <unistd.h>
+#endif
+
/* unistd.h defines _POSIX_VERSION on POSIX.1 systems. */
#if defined(DIRENT) || defined(_POSIX_VERSION)
#include <dirent.h>
@defmac AC_UNISTD_H
@maindex UNISTD_H
@vindex HAVE_UNISTD_H
-Define @code{HAVE_UNISTD_H} if the system has @file{unistd.h}. The way
-to check if the system supports POSIX.1 is:
+Define @code{HAVE_UNISTD_H} if the system has @file{unistd.h}. This
+macro is obsolete; instead, use @samp{AC_HAVE_HEADERS(unistd.h)}.
+
+The way to check if the system supports POSIX.1 is:
@example
@group
(so programs can periodically call @samp{alloca(0)} to garbage collect).
This variable is separate from @code{LIBOBJS} so multiple programs can
share the value of @code{ALLOCA} without needing to create an actual
-library.
+library, in case only some of them use the code in @code{LIBOBJS}.
If this macro finds @file{alloca.h}, it defines @code{HAVE_ALLOCA_H}.
@var{action-if-not-found}.
You can not check whether preprocessor symbols are defined this way,
-because they get expanded before @code{egrep} sees them. You can
-probably just put @code{#ifdef} directives in your C programs to detect
-them, but if you want to do the check in @code{configure} for some
-reason (perhaps to determine which of several files to include), then
-use @code{AC_PROGRAM_EGREP}, like this:
-
-@example
-AC_PROGRAM_EGREP(yes, [#include <stdio.h>
-#ifdef P_tmpdir
-yes
-#endif
-], AC_DEFINE(HAVE_P_TMPDIR))
-@end example
+because they get expanded before @code{egrep} sees them. But you can
+almost always detect them by simply using @code{#ifdef} directives in
+your C programs.
@end defmac
@defmac AC_PREFIX (@var{program})
@example
prefix = /usr/local
-exec_prefix = ${prefix}
+exec_prefix = $@{prefix@}
@end example
@noindent
projects / thirdparty / autoconf.git / commitdiff
