Go to the previous, next section.
These macros test for particular system features that packages might need or want to use. If you need to test for a kind of feature that none of these macros check for, you can probably do it by calling primitive test macros with appropriate arguments (see section Writing Tests).
These tests print messages telling the user which feature they're
checking for, and what they find. They cache their results for future
configure runs (see section Caching Results).
Some of these macros set output variables. See section Substitutions in Makefiles, for how to get their values. The phrase "define name" is used below as a shorthand to mean "define C preprocessor symbol name to the value 1". See section Defining C Preprocessor Symbols, for how to get those symbol definitions into your program.
These macros check for the presence or behavior of particular programs. They are used to choose between several alternative programs and to decide what to do once one has been chosen. If there is no macro specifically defined to check for a program you need, and you don't need to check for any special properties of it, then you can use one of the general program check macros.
These macros check for particular programs--whether they exist, and in some cases whether they support certain features.
@maindex DECL_YYTEXT
@cvindex YYTEXT_POINTER
@ovindex LEX_OUTPUT_ROOT
Define YYTEXT_POINTER if yytext is a `char *' instead
of a `char []'. Also set output variable LEX_OUTPUT_ROOT to
the base of the file name that the lexer generates; usually
`lex.yy', but sometimes something else. These results vary
according to whether lex or flex is being used.
@maindex PROG_AWK
@ovindex AWK
Check for mawk, gawk, nawk, and awk, in that
order, and set output variable AWK to the first one that it
finds. It tries mawk first because that is reported to be the
fastest implementation.
@maindex PROG_CC
@ovindex CC
@ovindex CFLAGS
Determine a C compiler to use. If CC is not already set in the
environment, check for gcc, and use cc if it's not found.
Set output variable CC to the name of the compiler found.
If using the GNU C compiler, set shell variable GCC to
`yes', empty otherwise. If output variable CFLAGS was
not already set, set it to `-g -O' for the GNU C compiler
(`-O' on systems where GCC does not accept `-g'), or `-g'
for other compilers.
@maindex PROG_CC_C_O
@cvindex NO_MINUS_C_MINUS_O
If the C compiler does not accept the `-c' and `-o' options
simultaneously, define NO_MINUS_C_MINUS_O.
@maindex PROG_CPP
@ovindex CPP
Set output variable CPP to a command that runs the
C preprocessor. If `$CC -E' doesn't work, it uses `/lib/cpp'.
It is only portable to run CPP on files with a `.c'
extension.
If the current language is C (see section Language Choice), many of the
specific test macros use the value of CPP indirectly by calling
AC_TRY_CPP, AC_CHECK_HEADER, AC_EGREP_HEADER, or
AC_EGREP_CPP.
@maindex PROG_CXX
@ovindex CXX
@ovindex CXXFLAGS
Determine a C++ compiler to use. Check if the environment variable
CXX or CCC (in that order) is set; if so, set output
variable CXX to its value. Otherwise search for a C++ compiler
under likely names (c++, g++, gcc, CC, and
cxx). If none of those checks succeed, as a last resort set
CXX to gcc.
If using the GNU C++ compiler, set shell variable GXX to
`yes', empty otherwise. If output variable CXXFLAGS was
not already set, set it to `-g -O' for the GNU C++ compiler
(`-O' on systems where G++ does not accept `-g'), or `-g'
for other compilers.
@maindex PROG_CXXCPP
@ovindex CXXCPP
Set output variable CXXCPP to a command that runs the
C++ preprocessor. If `$CXX -E' doesn't work, it uses `/lib/cpp'.
It is only portable to run CXXCPP on files with a `.c',
`.C', or `.cc' extension.
If the current language is C++ (see section Language Choice), many of the
specific test macros use the value of CXXCPP indirectly by
calling AC_TRY_CPP, AC_CHECK_HEADER,
AC_EGREP_HEADER, or AC_EGREP_CPP.
Macro: AC_PROG_GCC_TRADITIONAL
@maindex PROG_GCC_TRADITIONAL
@ovindex CC
Add `-traditional' to output variable CC if using the
GNU C compiler and ioctl does not work properly without
`-traditional'. That usually happens when the fixed header files
have not been installed on an old system. Since recent versions of the
GNU C compiler fix the header files automatically when installed, this
is becoming a less prevalent problem.
@maindex PROG_INSTALL
@ovindex INSTALL
@ovindex INSTALL_PROGRAM
@ovindex INSTALL_DATA
Set output variable INSTALL to the path of a BSD compatible
install program, if one is found in the current PATH.
Otherwise, set INSTALL to `dir/install-sh -c',
checking the directories specified to AC_CONFIG_AUX_DIR (or its
default directories) to determine dir (see section Creating Output Files). Also set
the variable INSTALL_PROGRAM to `${INSTALL}' and
INSTALL_DATA to `${INSTALL} -m 644'.
This macro screens out various instances of install known to not
work. It prefers to find a C program rather than a shell script, for
speed. Instead of `install-sh', it can also use `install.sh',
but that name is obsolete because some make programs have a rule
that creates `install' from it if there is no `Makefile'.
A copy of `install-sh' which you may use comes with Autoconf. If
you use AC_PROG_INSTALL, you must include either
`install-sh' or `install.sh' in your distribution, or
configure will produce an error message saying it can't find
them--even if the system you're on has a good install program.
This check is a safety measure to prevent you from accidentally leaving
that file out, which would prevent your package from installing on
systems that don't have a BSD-compatible install program.
If you need to use your own installation program because it has
features not found in standard install programs, there is no
reason to use AC_PROG_INSTALL; just put the pathname of your
program into your `Makefile.in' files.
@maindex PROG_LEX
@ovindex LEX
@ovindex LEXLIB
If flex is found, set output variable LEX to
`flex' and LEXLIB to `-lfl', if that library is in a
standard place. Otherwise set LEX to `lex' and
LEXLIB to `-ll'.
@maindex PROG_LN_S
@ovindex LN_S
If `ln -s' works on the current filesystem (the operating system
and filesystem support symbolic links), set output
variable LN_S to `ln -s', otherwise set it to `ln'.
@maindex PROG_RANLIB
@ovindex RANLIB
Set output variable RANLIB to `ranlib' if ranlib
is found, otherwise to `:' (do nothing).
@maindex PROG_YACC
@ovindex YACC
If bison is found, set output variable YACC to
`bison -y'. Otherwise, if byacc is found, set YACC
to `byacc'. Otherwise set YACC to `yacc'.
These macros are used to find programs not covered by the particular
test macros. If you need to check the behavior of a program as well as
find out whether it is present, you have to write your own test for
it (see section Writing Tests). If you need to check for a program that
might not be in the user's PATH, you can temporarily add to it:
ac_save_path="$PATH" PATH=/usr/libexec:/usr/sbin:/usr/etc:/etc AC_PATH_PROG(INETD, inetd, /usr/libexec/inetd) PATH="$ac_save_path"
Macro: AC_CHECK_PROG (variable, prog-to-check-for, value-if-found [, value-if-not-found])
@maindex CHECK_PROG
Check whether program prog-to-check-for exists in PATH. If
it is found, set variable to value-if-found, otherwise to
value-if-not-found, if given. If variable was already set,
do nothing. Calls AC_SUBST for variable.
Macro: AC_CHECK_PROGS (variable, progs-to-check-for [, value-if-not-found])
@maindex CHECK_PROGS
Check for each program in the whitespace-separated list
progs-to-check-for exists in PATH. If it is found, set
variable to the name of that program. Otherwise, continue
checking the next program in the list. If none of the programs in the
list are found, set variable to value-if-not-found; if
value-if-not-found is not specified, the value of variable
is not changed. Calls AC_SUBST for variable.
Macro: AC_CHECK_TOOL (variable, prog-to-check-for [, value-if-not-found])
@maindex CHECK_TOOL
Like AC_CHECK_PROG, but first looks for prog-to-check-for
with a prefix of the host type as determined by AC_CANONICAL_HOST,
followed by a dash (see section Getting the Canonical System Type). For example, if the user
runs `configure --host=i386-gnu', then this call:
AC_CHECK_TOOL(RANLIB, ranlib, :)sets
RANLIB to `i386-gnu-ranlib' if that program exists in
PATH, or to `ranlib' if that program exists in PATH,
or to `:' if neither program exists.
Macro: AC_PATH_PROG (variable, prog-to-check-for [, value-if-not-found])
@maindex PATH_PROG
Like AC_CHECK_PROG, but set variable to the entire
path of prog-to-check-for if found.
Macro: AC_PATH_PROGS (variable, progs-to-check-for [, value-if-not-found])
@maindex PATH_PROGS
Like AC_CHECK_PROGS, but if any of progs-to-check-for
are found, set variable to the entire path of the program
found.
The following macros check for the presence of certain C library archive files.
Macro: AC_CHECK_LIB (library, function [, action-if-found [, action-if-not-found [, other-libraries]]])
@maindex CHECK_LIB Try to ensure that C function function is available by checking whether a test C program can be linked with the library library to get the function. library is the base name of the library; e.g., to check for `-lmp', use `mp' as the library argument.
action-if-found is a list of shell commands to run if the link
with the library succeeds; action-if-not-found is a list of shell
commands to run if the link fails. If action-if-found and
action-if-not-found are not specified, the default action is to
add `-llibrary' to LIBS and define
`HAVE_LIBlibrary' (in all capitals).
If linking with library results in unresolved symbols, which would be resolved by linking with additional libraries, give those libraries as the other-libraries argument, separated by spaces: `-lXt -lX11'. Otherwise this macro will fail to detect that library is present, because linking the test program will always fail with unresolved symbols.
Macro: AC_HAVE_LIBRARY (library, [, action-if-found [, action-if-not-found [, other-libraries]]])
@maindex HAVE_LIBRARY
This macro is equivalent to calling AC_CHECK_LIB with a
function argument of main. In addition, library can
be written as any of `foo', `-lfoo', or `libfoo.a'. In
all of those cases, the compiler is passed `-lfoo'. However,
library can not be a shell variable; it must be a literal name.
This macro is considered obsolete.
The following macros check for particular C library functions. If there is no macro specifically defined to check for a function you need, and you don't need to check for any special properties of it, then you can use one of the general function check macros.
These macros check for particular C functions--whether they exist, and in some cases how they respond when given certain arguments.
@maindex FUNC_ALLOCA
@cvindex C_ALLOCA
@cvindex HAVE_ALLOCA_H
@ovindex ALLOCA
Check how to get alloca. Tries to get a builtin version by
checking for `alloca.h' or the predefined C preprocessor macros
__GNUC__ and _AIX. If this macro finds `alloca.h',
it defines HAVE_ALLOCA_H.
If those attempts fail, it looks for the function in the standard C
library. If any of those methods succeed, it defines
HAVE_ALLOCA. Otherwise, it sets the output variable
ALLOCA to `alloca.o' and defines C_ALLOCA (so
programs can periodically call `alloca(0)' to garbage collect).
This variable is separate from LIBOBJS so multiple programs can
share the value of ALLOCA without needing to create an actual
library, in case only some of them use the code in LIBOBJS.
This macro does not try to get alloca from the System V R3
`libPW' or the System V R4 `libucb' because those libraries
contain some incompatible functions that cause trouble. Some versions
do not even contain alloca or contain a buggy version. If you
still want to use their alloca, use ar to extract
`alloca.o' from them instead of compiling `alloca.c'.
Source files that use alloca should start with a piece of code
like the following, to declare it properly. In some versions
of AIX, the declaration of alloca must precede everything else
except for comments and preprocessor directives. The #pragma
directive is indented so that pre-ANSI C compilers will ignore it,
rather than choke on it.
/* AIX requires this to be the first thing in the file. */ #ifdef __GNUC__ # define alloca __builtin_alloca #else # if HAVE_ALLOCA_H # include <alloca.h> # else # ifdef _AIX #pragma alloca # else # ifndef alloca /* predefined by HP cc +Olibcalls */ char *alloca (); # endif # endif # endif #endif
@maindex FUNC_CLOSEDIR_VOID
@cvindex CLOSEDIR_VOID
If the closedir function does not return a meaningful value,
define CLOSEDIR_VOID. Otherwise, callers ought to check its
return value for an error indicator.
@maindex FUNC_GETLOADAVG
@cvindex SVR4
@cvindex DGUX
@cvindex UMAX
@cvindex UMAX4_3
@cvindex NLIST_STRUCT
@cvindex NLIST_NAME_UNION
@cvindex GETLODAVG_PRIVILEGED
@cvindex NEED_SETGID
@ovindex LIBOBJS
@ovindex NEED_SETGID
@ovindex KMEM_GROUP
Check how to get the system load averages. If the system has the
getloadavg function, this macro defines HAVE_GETLOADAVG,
and adds to LIBS any libraries needed to get that function.
Otherwise, it adds `getloadavg.o' to the output variable
LIBOBJS, and possibly defines several other C preprocessor
macros and output variables:
SVR4, DGUX, UMAX, or UMAX4_3 if
on those systems.
NLIST_STRUCT.
NLIST_NAME_UNION.
LDAV_PRIVILEGED,
programs need to be installed specially on this system for
getloadavg to work, and this macro defines
GETLOADAVG_PRIVILEGED.
NEED_SETGID. The value is
`true' if special installation is required, `false' if not.
If NEED_SETGID is `true', this macro sets KMEM_GROUP
to the name of the group that should own the installed program.
@maindex FUNC_GETMNTENT
@cvindex HAVE_GETMNTENT
Check for getmntent in the `sun' and `seq'
libraries, for Irix 4 and PTX, respectively. Then, if getmntent is
available, define HAVE_GETMNTENT.
@maindex FUNC_GETPGRP
@cvindex GETPGRP_VOID
If getpgrp takes no argument (the POSIX.1 version), define
GETPGRP_VOID. Otherwise, it is the BSD version, which takes a
process ID as an argument. This macro does not check whether
getpgrp exists at all; if you need to work in that situation,
first call AC_CHECK_FUNC for getpgrp.
@maindex FUNC_MEMCMP
@ovindex LIBOBJS
If the memcmp function is not available, or does not work on
8-bit data (like the one on SunOS 4.1.3), add `memcmp.o' to output
variable LIBOBJS.
@maindex FUNC_MMAP
@cvindex HAVE_MMAP
If the mmap function exists and works correctly on memory mapped
files, define HAVE_MMAP.
Macro: AC_FUNC_SETVBUF_REVERSED
@maindex FUNC_SETVBUF_REVERSED
@cvindex SETVBUF_REVERSED
If setvbuf takes the buffering type as its second argument and
the buffer pointer as the third, instead of the other way around, define
SETVBUF_REVERSED. This is the case on System V before release 3.
@maindex FUNC_STRCOLL
@cvindex HAVE_STRCOLL
If the strcoll function exists and works correctly, define
HAVE_STRCOLL. This does a bit more than
`AC_CHECK_FUNCS(strcoll)', because some systems have incorrect
definitions of strcoll, which should not be used.
@maindex FUNC_STRFTIME
@cvindex HAVE_STRFTIME
Check for strftime in the `intl' library, for SCO UNIX.
Then, if strftime is available, define HAVE_STRFTIME.
@maindex FUNC_UTIME_NULL
@cvindex HAVE_UTIME_NULL
If `utime(file, NULL)' sets file's timestamp to
the present, define HAVE_UTIME_NULL.
@maindex FUNC_VFORK
@cvindex HAVE_VFORK_H
@cvindex vfork
If `vfork.h' is found, define HAVE_VFORK_H. If a working
vfork is not found, define vfork to be fork. This
macro checks for several known errors in implementations of vfork
and considers the system to not have a working vfork if it
detects any of them. It is not considered to be an implementation error
if a child's invocation of signal modifies the parent's signal
handler, since child processes rarely change their signal handlers.
@maindex FUNC_VPRINTF
@cvindex HAVE_VPRINTF
@cvindex HAVE_DOPRNT
If vprintf is found, define HAVE_VPRINTF. Otherwise, if
_doprnt is found, define HAVE_DOPRNT. (If vprintf
is available, you may assume that vfprintf and vsprintf
are also available.)
@maindex FUNC_WAIT3
@cvindex HAVE_WAIT3
If wait3 is found and fills in the contents of its third argument
(a `struct rusage *'), which HP-UX does not do, define
HAVE_WAIT3.
These macros are used to find functions not covered by the particular
test macros. If the functions might be in libraries other than the
default C library, first call AC_CHECK_LIB for those libraries.
If you need to check the behavior of a function as well as find out
whether it is present, you have to write your own test for
it (see section Writing Tests).
Macro: AC_CHECK_FUNC (function, action-if-found [, action-if-not-found])
@maindex CHECK_FUNC
If C function function is available, run shell commands
action-if-found, otherwise action-if-not-found. If you just
want to define a symbol if the function is available, consider using
AC_CHECK_FUNCS instead. This macro checks for functions with C
linkage even when AC_LANG_CPLUSPLUS has been called, since C++ is
more standardized than C is. (see section Language Choice, for more
information about selecting the language for checks.)
Macro: AC_CHECK_FUNCS (function... [, action-if-found [, action-if-not-found]])
@maindex CHECK_FUNCS
@cvindex HAVE_function
For each given function in the whitespace-separated argument list
that is available, define HAVE_function (in all capitals). If
action-if-found is given, it is additional shell code to execute
when one of the functions is found. You can give it a value of
`break' to break out of the loop on the first match. If
action-if-not-found is given, it is executed when one of the
functions is not found.
Macro: AC_REPLACE_FUNCS (function-name...)
@maindex REPLACE_FUNCS
@ovindex LIBOBJS
For each given function-name in the whitespace-separated argument
list that is not in the C library, add `function-name.o' to
the value of the output variable LIBOBJS.
The following macros check for the presence of certain C header files. If there is no macro specifically defined to check for a header file you need, and you don't need to check for any special properties of it, then you can use one of the general header file check macros.
These macros check for particular system header files--whether they exist, and in some cases whether they declare certain symbols.
@maindex DECL_SYS_SIGLIST
@cvindex SYS_SIGLIST_DECLARED
Define SYS_SIGLIST_DECLARED if the variable sys_siglist is
declared in a system header file, either `signal.h' or
`unistd.h'.
@maindex DIR_HEADER
@cvindex DIRENT
@cvindex SYSDIR
@cvindex SYSNDIR
@cvindex NDIR
@cvindex VOID_CLOSEDIR
Like calling AC_HEADER_DIRENT and AC_FUNC_CLOSEDIR_VOID,
but defines a different set of C preprocessor macros to indicate which
header file is found. This macro and the names it defines are
considered obsolete. The names it defines are:
DIRENT
SYSNDIR
SYSDIR
NDIR
In addition, if the closedir function does not return a
meaningful value, define VOID_CLOSEDIR.
@maindex HEADER_DIRENT @cvindex HAVE_DIRENT_H @cvindex HAVE_NDIR_H @cvindex HAVE_SYS_DIR_H @cvindex HAVE_SYS_NDIR_H Check for the following header files, and for the first one that is found and defines `DIR', define the listed C preprocessor macro:
HAVE_DIRENT_H
HAVE_SYS_NDIR_H
HAVE_SYS_DIR_H
HAVE_NDIR_H
The directory library declarations in the source code should look something like the following:
#if HAVE_DIRENT_H # include <dirent.h> # define NAMLEN(dirent) strlen((dirent)->d_name) #else # define dirent direct # define NAMLEN(dirent) (dirent)->d_namlen # if HAVE_SYS_NDIR_H # include <sys/ndir.h> # endif # if HAVE_SYS_DIR_H # include <sys/dir.h> # endif # if HAVE_NDIR_H # include <ndir.h> # endif #endif
Using the above declarations, the program would declare variables to be
type struct dirent, not struct direct, and would access
the length of a directory entry name by passing a pointer to a
struct dirent to the NAMLEN macro.
This macro also checks for the SCO Xenix `dir' and `x' libraries.
@maindex HEADER_MAJOR
@cvindex MAJOR_IN_MKDEV
@cvindex MAJOR_IN_SYSMACROS
If `sys/types.h' does not define major, minor, and
makedev, but `sys/mkdev.h' does, define
MAJOR_IN_MKDEV; otherwise, if `sys/sysmacros.h' does, define
MAJOR_IN_SYSMACROS.
@maindex HEADER_STDC
@cvindex STDC_HEADERS
Define STDC_HEADERS if the system has ANSI C header files.
Specifically, this macro checks for `stdlib.h', `stdarg.h',
`string.h', and `float.h'; if the system has those, it
probably has the rest of the ANSI C header files. This macro also
checks whether `string.h' declares memchr (and thus
presumably the other mem functions), whether `stdlib.h'
declare free (and thus presumably malloc and other related
functions), and whether the `ctype.h' macros work on characters
with the high bit set, as ANSI C requires.
Use STDC_HEADERS instead of __STDC__ to determine whether
the system has ANSI-compliant header files (and probably C library
functions) because many systems that have GCC do not have ANSI C header
files.
On systems without ANSI C 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 systems contain a mix of functions ANSI and BSD; some are mostly ANSI but lack `memmove'; some define the BSD functions as macros in `string.h' or `strings.h'; some have only the BSD functions but `string.h'; some declare the memory functions in `memory.h', some in `string.h'; etc. It is probably sufficient to check for one string function and one memory function; if the library has the ANSI versions of those then it probably has most of the others. If you put the following in `configure.in':
AC_HEADER_STDC AC_CHECK_FUNCS(strchr memcpy)
then, in your code, you can put declarations like this:
#if STDC_HEADERS # include <string.h> #else # ifndef HAVE_STRCHR # define strchr index # define strrchr rindex # endif char *strchr (), *strrchr (); # ifndef HAVE_MEMCPY # define memcpy(d, s, n) bcopy ((s), (d), (n)) # define memmove(d, s, n) bcopy ((s), (d), (n)) # endif #endif
If you use a function like memchr, memset, strtok,
or strspn, which have no BSD equivalent, then macros won't
suffice; 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 memchr
for example, put it in `memchr.c' and use
`AC_REPLACE_FUNCS(memchr)'.
@maindex HEADER_SYS_WAIT
@cvindex HAVE_SYS_WAIT_H
If `sys/wait.h' exists and is compatible with POSIX.1, define
HAVE_SYS_WAIT_H. Incompatibility can occur if `sys/wait.h'
does not exist, or if it uses the old BSD union wait instead of
int to store a status value. If `sys/wait.h' is not POSIX.1
compatible, then instead of including it, define the POSIX.1 macros with
their usual interpretations. Here is an example:
#include <sys/types.h> #if HAVE_SYS_WAIT_H # include <sys/wait.h> #endif #ifndef WEXITSTATUS # define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8) #endif #ifndef WIFEXITED # define WIFEXITED(stat_val) (((stat_val) & 255) == 0) #endif
@maindex MEMORY_H
@cvindex NEED_MEMORY_H
Define NEED_MEMORY_H if memcpy, memcmp, etc. are
not declared in `string.h' and `memory.h' exists. This macro
is obsolete; instead, use AC_CHECK_HEADERS(memory.h). See the
example for AC_HEADER_STDC.
@maindex UNISTD_H
@cvindex HAVE_UNISTD_H
Define HAVE_UNISTD_H if the system has `unistd.h'. This
macro is obsolete; instead, use `AC_CHECK_HEADERS(unistd.h)'.
The way to check if the system supports POSIX.1 is:
#if HAVE_UNISTD_H # include <sys/types.h> # include <unistd.h> #endif #ifdef _POSIX_VERSION /* Code for POSIX.1 systems. */ #endif
@cvindex _POSIX_VERSION
_POSIX_VERSION is defined when `unistd.h' is included on
POSIX.1 systems. If there is no `unistd.h', it is definitely not a
POSIX.1 system. However, some non-POSIX.1 systems do have `unistd.h'.
@maindex USG
@cvindex USG
Define USG if the system does not have `strings.h',
rindex, bzero, etc. This implies that it has
`string.h', strrchr, memset, etc.
The symbol USG is obsolete. Instead of this macro, see the
example for AC_HEADER_STDC.
These macros are used to find system header files not covered by the particular test macros. If you need to check the contents of a header as well as find out whether it is present, you have to write your own test for it (see section Writing Tests).
Macro: AC_CHECK_HEADER (header-file, action-if-found [, action-if-not-found])
@maindex CHECK_HEADER
If the system header file header-file exists, execute shell commands
action-if-found, otherwise execute action-if-not-found. If
you just want to define a symbol if the header file is available,
consider using AC_CHECK_HEADERS instead.
Macro: AC_CHECK_HEADERS (header-file... [, action-if-found [, action-if-not-found]])
@maindex CHECK_HEADERS
@cvindex HAVE_header
For each given system header file header-file in the
whitespace-separated argument list that exists, define
HAVE_header-file (in all capitals). If action-if-found
is given, it is additional shell code to execute when one of the header
files is found. You can give it a value of `break' to break out of
the loop on the first match. If action-if-not-found is given, it
is executed when one of the header files is not found.
The following macros check for certain structures or structure members.
To check structures not listed here, use AC_EGREP_CPP
(see section Examining Declarations) or AC_TRY_COMPILE
(see section Examining Syntax).
@maindex HEADER_STAT
@maindex STAT_MACROS_BROKEN
If the macros S_ISDIR, S_ISREG et al. defined in
`sys/stat.h' do not work properly (returning false positives),
define STAT_MACROS_BROKEN. This is the case on Tektronix UTekV,
Amdahl UTS and Motorola System V/88.
@maindex HEADER_TIME
@cvindex TIME_WITH_SYS_TIME
If a program may include both `time.h' and `sys/time.h',
define TIME_WITH_SYS_TIME. On some older systems,
`sys/time.h' includes `time.h', but `time.h' is not
protected against multiple inclusion, so programs should not explicitly
include both files. This macro is useful in programs that use, for
example, struct timeval or struct timezone as well as
struct tm. It is best used in conjunction with
HAVE_SYS_TIME_H, which can be checked for using
AC_CHECK_HEADERS(sys/time.h).
#if TIME_WITH_SYS_TIME # include <sys/time.h> # include <time.h> #else # if HAVE_SYS_TIME_H # include <sys/time.h> # else # include <time.h> # endif #endif
@maindex STRUCT_ST_BLKSIZE
@cvindex HAVE_ST_BLKSIZE
If struct stat contains an st_blksize member, define
HAVE_ST_BLKSIZE.
@maindex STRUCT_ST_BLOCKS
@cvindex HAVE_ST_BLOCKS
@ovindex LIBOBJS
If struct stat contains an st_blocks member, define
HAVE_ST_BLOCKS. Otherwise, add `fileblocks.o' to the
output variable LIBOBJS.
@maindex STRUCT_ST_RDEV
@cvindex HAVE_ST_RDEV
If struct stat contains an st_rdev member, define
HAVE_ST_RDEV.
@maindex STRUCT_TM
@cvindex TM_IN_SYS_TIME
If `time.h' does not define struct tm, define
TM_IN_SYS_TIME, which means that including `sys/time.h'
had better define struct tm.
@maindex STRUCT_TIMEZONE
@cvindex HAVE_TM_ZONE
@cvindex HAVE_TZNAME
Figure out how to get the current timezone. If struct tm has a
tm_zone member, define HAVE_TM_ZONE. Otherwise, if the
external array tzname is found, define HAVE_TZNAME.
The following macros check for C typedefs. If there is no macro specifically defined to check for a typedef you need, and you don't need to check for any special properties of it, then you can use a general typedef check macro.
These macros check for particular C typedefs in `sys/types.h' and `stdlib.h' (if it exists).
@maindex TYPE_GETGROUPS
@cvindex GETGROUPS_T
Define GETGROUPS_T to be whichever of gid_t or int
is the base type of the array argument to getgroups.
@maindex TYPE_MODE_T
@cvindex mode_t
If mode_t is not defined, define mode_t to be int.
@maindex TYPE_OFF_T
@cvindex off_t
If off_t is not defined, define off_t to be long.
@maindex TYPE_PID_T
@cvindex pid_t
If pid_t is not defined, define pid_t to be int.
@maindex TYPE_SIGNAL
@cvindex RETSIGTYPE
If `signal.h' declares signal as returning a pointer to a
function returning void, define RETSIGTYPE to be
void; otherwise, define it to be int.
Define signal handlers as returning type RETSIGTYPE:
RETSIGTYPE
hup_handler ()
{
...
}
@maindex TYPE_SIZE_T
@cvindex size_t
If size_t is not defined, define size_t to be
unsigned.
@maindex TYPE_UID_T
@cvindex uid_t
@cvindex gid_t
If uid_t is not defined, define uid_t to be int and
gid_t to be int.
This macro is used to check for typedefs not covered by the particular test macros.
Macro: AC_CHECK_TYPE (type, default)
@maindex CHECK_TYPE If the type type is not defined in `sys/types.h' or `stdlib.h' (if it exists), define it to be the C (or C++) builtin type default; e.g., `short' or `unsigned'.
The following macros check for C compiler or machine architecture
features. To check for characteristics not listed here, use
AC_TRY_COMPILE (see section Examining Syntax) or AC_TRY_RUN
(see section Checking Run Time Behavior)
@maindex C_BIGENDIAN
@cvindex WORDS_BIGENDIAN
If words are stored with the most significant byte first (like Motorola
and SPARC, but not Intel and VAX, CPUs), define WORDS_BIGENDIAN.
@maindex C_CONST
@cvindex const
If the C compiler does not fully support the keyword const,
define const to be empty. Some C compilers that do not define
__STDC__ do support const; some compilers that define
__STDC__ do not completely support const. Programs can
simply use const as if every C compiler supported it; for those
that don't, the `Makefile' or configuration header file will define
it as empty.
@maindex C_INLINE
@cvindex inline
If the C compiler supports the keyword inline, do nothing.
Otherwise define inline to __inline__ or __inline
if it accepts one of those, otherwise define inline to be empty.
@maindex C_CHAR_UNSIGNED
@cvindex __CHAR_UNSIGNED__
If the C type char is unsigned, define __CHAR_UNSIGNED__,
unless the C compiler predefines it.
@maindex C_LONG_DOUBLE
@cvindex HAVE_LONG_DOUBLE
If the C compiler supports the long double type, define
HAVE_LONG_DOUBLE. Some C compilers that do not define
__STDC__ do support the long double type; some compilers
that define __STDC__ do not support long double.
@maindex CHECK_SIZEOF
Define SIZEOF_uctype to be the size in bytes of the C (or
C++) builtin type type, e.g. `int' or `char *'. If
`type' is unknown to the compiler, it gets a size of 0. uctype
is type, with lowercase converted to uppercase, spaces changed to
underscores, and asterisks changed to `P'. For example, the call
AC_CHECK_SIZEOF(int *)defines
SIZEOF_INT_P to be 8 on DEC Alpha AXP systems.
@maindex INT_16_BITS
@cvindex INT_16_BITS
If the C type int is 16 bits wide, define INT_16_BITS.
This macro is obsolete; it is more general to use
`AC_CHECK_SIZEOF(int)' instead.
@maindex LONG_64_BITS
@cvindex LONG_64_BITS
If the C type long int is 64 bits wide, define
LONG_64_BITS. This macro is obsolete; it is more general to use
`AC_CHECK_SIZEOF(long)' instead.
The following macros check for operating system services or capabilities.
@maindex SYS_INTERPRETER
Check whether the system supports starting scripts with a line of the
form `#! /bin/csh' to select the interpreter to use for the script.
After running this macro, shell code in configure.in can check
the variable ac_cv_sys_interpreter; it will be set to `yes'
if the system supports `#!', `no' if not.
@maindex PATH_X
Try to locate the X Window System include files and libraries. If the
user gave the command line options `--x-includes=dir' and
`--x-libraries=dir', use those directories. If either or
both were not given, get the missing values by running xmkmf on a
trivial `Imakefile' and examining the `Makefile' that it
produces. If that fails (such as if xmkmf is not present), look
for them in several directories where they often reside. If either
method is successful, set the shell variables x_includes and
x_libraries to their locations, unless they are in directories
the compiler searches by default.
If both methods fail, or the user gave the command line option
`--without-x', set the shell variable no_x to `yes';
otherwise set it to the empty string.
@maindex PATH_XTRA
@ovindex X_CFLAGS
@ovindex X_LIBS
@ovindex X_EXTRA_LIBS
@ovindex X_PRE_LIBS
An enhanced version of AC_PATH_X. It adds the C compiler flags that
X needs to output variable X_CFLAGS, and the X linker flags to
X_LIBS. If X is not available, adds `-DX_DISPLAY_MISSING' to
X_CFLAGS.
This macro also checks for special libraries that some systems need in
order to compile X programs. It adds any that the system needs to
output variable X_EXTRA_LIBS. And it checks for special X11R6
libraries that need to be linked with before `-lX11', and adds any
found to the output variable X_PRE_LIBS.
@maindex SYS_LONG_FILE_NAMES
@cvindex HAVE_LONG_FILE_NAMES
If the system supports file names longer than 14 characters, define
HAVE_LONG_FILE_NAMES.
Macro: AC_SYS_RESTARTABLE_SYSCALLS
@maindex SYS_RESTARTABLE_SYSCALLS
@cvindex HAVE_RESTARTABLE_SYSCALLS
If the system automatically restarts a system call that is interrupted
by a signal, define HAVE_RESTARTABLE_SYSCALLS.
The following macros check for certain operating systems that need special treatment for some programs, due to exceptional oddities in their header files or libraries. These macros are warts; they will be replaced by a more systematic approach, based on the functions they make available or the environments they provide.
@maindex AIX
@cvindex _ALL_SOURCE
If on AIX, define _ALL_SOURCE. Allows the use of some BSD
functions. Should be called before any macros that run the C compiler.
@maindex DYNIX_SEQ
If on Dynix/PTX (Sequent UNIX), add `-lseq' to output
variable LIBS. This macro is obsolete; instead, use
AC_FUNC_GETMNTENT.
@maindex IRIX_SUN
If on IRIX (Silicon Graphics UNIX), add `-lsun' to output variable
LIBS. This macro is obsolete. If you were using it to get
getmntent, use AC_FUNC_GETMNTENT instead. If you used it
for the NIS versions of the password and group functions, use
`AC_CHECK_LIB(sun, getpwnam)'.
@maindex ISC_POSIX
@cvindex _POSIX_SOURCE
@ovindex CC
If on a POSIXized ISC UNIX, define _POSIX_SOURCE and add
`-posix' (for the GNU C compiler) or `-Xp' (for other C
compilers) to output variable CC. This allows the use of
POSIX facilities. Must be called after AC_PROG_CC and before
any other macros that run the C compiler.
@maindex MINIX
@cvindex _MINIX
@cvindex _POSIX_SOURCE
@cvindex _POSIX_1_SOURCE
If on Minix, define _MINIX and _POSIX_SOURCE and define
_POSIX_1_SOURCE to be 2. This allows the use of POSIX
facilities. Should be called before any macros that run the C compiler.
@maindex SCO_INTL
@ovindex LIBS
If on SCO UNIX, add `-lintl' to output variable LIBS.
This macro is obsolete; instead, use AC_FUNC_STRFTIME.
@maindex XENIX_DIR
@ovindex LIBS
If on Xenix, add `-lx' to output variable LIBS. Also, if
`dirent.h' is being used, add `-ldir' to LIBS. This
macro is obsolete; use AC_HEADER_DIRENT instead.
Go to the previous, next section.