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These macros check for particular C functions--whether they exist, and in some cases how they respond when given certain arguments.
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. */ #ifndef __GNUC__ # 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
chown function is available and works (in particular, it
should accept @option{-1} for uid and gid), define
HAVE_CHOWN.
closedir function does not return a meaningful value,
define CLOSEDIR_VOID. Otherwise, callers ought to check its
return value for an error indicator.
error_at_line function is not found, require an
AC_LIBOBJ replacement of `error'.
fnmatch function is available and works (unlike the one on
Solaris 2.4), define HAVE_FNMATCH.
fork and vfork functions. If a
working fork is found, define HAVE_WORKING_FORK. This macro
checks whether fork is just a stub by trying to run it.
If `vfork.h' is found, define HAVE_VFORK_H. If a working
vfork is found, define HAVE_WORKING_VFORK. Otherwise,
define vfork to be fork for backward compatibility with
previous versions of @command{autoconf}. 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.
Since this macro defines vfork only for backward compatibility with
previous versions of @command{autoconf} you're encouraged to define it
yourself in new code:
#if !HAVE_WORKING_VFORK # define vfork fork #endif
fseeko function is available, define HAVE_FSEEKO.
Define _LARGEFILE_SOURCE if necessary.
getgroups function is available and works (unlike on
Ultrix 4.3, where `getgroups (0, 0)' always fails), define
HAVE_GETGROUPS. Set GETGROUPS_LIBS to any libraries
needed to get that function. This macro runs AC_TYPE_GETGROUPS.
getloadavg function, define HAVE_GETLOADAVG, and set
GETLOADAVG_LIBS to any libraries needed to get that function.
Also add GETLOADAVG_LIBS to LIBS.
Otherwise, require an AC_LIBOBJ replacement (`getloadavg.c')
of `getloadavg', and possibly define several other C preprocessor
macros and output variables:
C_GETLOADAVG.
SVR4, DGUX, UMAX, or UMAX4_3 if on
those systems.
NLIST_STRUCT.
HAVE_STRUCT_NLIST_N_UN_N_NAME. The obsolete symbol
NLIST_NAME_UNION is still defined, but do not depend upon it.
getloadavg to work. In this case, define
GETLOADAVG_PRIVILEGED, set the output variable NEED_SETGID
to `true' (and otherwise to `false'), and set
KMEM_GROUP to the name of the group that should own the installed
program.
getmntent in the `sun', `seq', and `gen'
libraries, for Irix 4, PTX, and Unixware, respectively. Then, if
getmntent is available, define HAVE_GETMNTENT.
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.
lstat should treat
`link/' the same as `link/.'. However, many older
lstat implementations incorrectly ignore trailing slashes.
It is safe to assume that if lstat incorrectly ignores
trailing slashes, then other symbolic-link-aware functions like
unlink and unlink also incorrectly ignore trailing slashes.
If lstat behaves properly, define
LSTAT_FOLLOWS_SLASHED_SYMLINK, otherwise require an
AC_LIBOBJ replacement of lstat.
malloc works correctly (`malloc (0)' returns a valid
pointer), define HAVE_MALLOC.
memcmp function is not available, or does not work on
8-bit data (like the one on SunOS 4.1.3), or fails when comparing 16
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
AC_LIBOBJ replacement for `memcmp'.
mktime function is not available, or does not work
correctly, require an AC_LIBOBJ replacement for `mktime'.
mmap function exists and works correctly, define
HAVE_MMAP. Only checks private fixed mapping of already-mapped
memory.
HAVE_OBSTACK, else require an
AC_LIBOBJ replacement for `obstack'.
select function's arguments, and defines those types
in SELECT_TYPE_ARG1, SELECT_TYPE_ARG234, and
SELECT_TYPE_ARG5 respectively. SELECT_TYPE_ARG1 defaults
to `int', SELECT_TYPE_ARG234 defaults to `int *',
and SELECT_TYPE_ARG5 defaults to `struct timeval *'.
setpgrp takes no argument (the POSIX.1 version), define
SETPGRP_VOID. Otherwise, it is the BSD version, which takes
two process IDs as arguments. This macro does not check whether
setpgrp exists at all; if you need to work in that situation,
first call AC_CHECK_FUNC for setpgrp.
stat or lstat have the bug that it
succeeds when given the zero-length file name argument. The stat
and lstat from SunOS 4.1.4 and the Hurd (as of 1998-11-01) do
this.
If it does, then define HAVE_STAT_EMPTY_STRING_BUG (or
HAVE_LSTAT_EMPTY_STRING_BUG) and ask for an AC_LIBOBJ
replacement of it.
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.
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 that should not be used.
strtod function does not exist or doesn't work correctly,
ask for an AC_LIBOBJ replacement of `strtod'. In this case,
because `strtod.c' is likely to need `pow', set the output
variable POW_LIB to the extra library needed.
strerror_r is available, define HAVE_STRERROR_R. If
its implementation correctly returns a char *, define
HAVE_WORKING_STRERROR_R. On at least DEC UNIX 4.0[A-D] and HP-UX
B.10.20, strerror_r returns int. Actually, this tests
only whether it returns a scalar or an array, but that should be enough.
This is used by the common `error.c'.
strftime in the `intl' library, for SCO UNIX.
Then, if strftime is available, define HAVE_STRFTIME.
HAVE_UTIME_NULL.
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.)
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