These macros check for particular system header files—whether they exist, and in some cases whether they declare certain symbols.
Check whether stdbool.h exists and conforms to C99 or later,
and cache the result in the ac_cv_header_stdbool_h variable.
If the type _Bool is defined, define HAVE__BOOL to 1.
This macro is obsolescent, as all current C compilers have stdbool.h, a header that is itself obsolescent as of C23.
This macro is intended for use by Gnulib (see Gnulib) and other
packages that supply a substitute stdbool.h on platforms lacking
a conforming one. The AC_HEADER_STDBOOL macro is better for code
that explicitly checks for stdbool.h.
Check whether to enable assertions in the style of assert.h.
Assertions are enabled by default, but the user can override this by
invoking configure with the --disable-assert option.
Check for the following header files. For the first one that is found and defines ‘DIR’, define the listed C preprocessor macro:
| dirent.h | HAVE_DIRENT_H |
| sys/ndir.h | HAVE_SYS_NDIR_H |
| sys/dir.h | HAVE_SYS_DIR_H |
| ndir.h | HAVE_NDIR_H |
The directory-library declarations in your source code should look something like the following:
#include <sys/types.h> #ifdef HAVE_DIRENT_H # include <dirent.h> # define NAMLEN(dirent) strlen ((dirent)->d_name) #else # define dirent direct # define NAMLEN(dirent) ((dirent)->d_namlen) # ifdef HAVE_SYS_NDIR_H # include <sys/ndir.h> # endif # ifdef HAVE_SYS_DIR_H # include <sys/dir.h> # endif # ifdef HAVE_NDIR_H # include <ndir.h> # endif #endif
Using the above declarations, the program would declare variables to be
of 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.
This macro is obsolescent, as all current systems with directory
libraries have <dirent.h>. New programs need not use this macro.
Also see AC_STRUCT_DIRENT_D_INO and
AC_STRUCT_DIRENT_D_TYPE (see Particular Structure Checks).
Detect the headers required to use makedev, major, and
minor. These functions may be defined by sys/mkdev.h,
sys/sysmacros.h, or sys/types.h.
AC_HEADER_MAJOR defines MAJOR_IN_MKDEV if they are in
sys/mkdev.h, or MAJOR_IN_SYSMACROS if they are in
sys/sysmacros.h. If neither macro is defined, they are either in
sys/types.h or unavailable.
To properly use these functions, your code should contain something like:
#include <sys/types.h> #ifdef MAJOR_IN_MKDEV # include <sys/mkdev.h> #elif defined MAJOR_IN_SYSMACROS # include <sys/sysmacros.h> #endif
Note: Configure scripts built with Autoconf 2.69 or earlier will not
detect a problem if sys/types.h contains definitions of
major, minor, and/or makedev that trigger compiler
warnings upon use. This is known to occur with GNU libc 2.25, where
those definitions are being deprecated to reduce namespace pollution.
If it is not practical to use Autoconf 2.70 to regenerate the configure
script of affected software, you can work around the problem by setting
‘ac_cv_header_sys_types_h_makedev=no’, as an argument to
configure or as part of a config.site site default file
(see Setting Site Defaults).
Checks for header resolv.h, checking for prerequisites first. To properly use resolv.h, your code should contain something like the following:
#ifdef HAVE_SYS_TYPES_H # include <sys/types.h> #endif #ifdef HAVE_NETINET_IN_H # include <netinet/in.h> /* inet_ functions / structs */ #endif #ifdef HAVE_ARPA_NAMESER_H # include <arpa/nameser.h> /* DNS HEADER struct */ #endif #ifdef HAVE_NETDB_H # include <netdb.h> #endif #include <resolv.h>
If the macros S_ISDIR, S_ISREG, etc. 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.
This macro is obsolescent, as no current systems have the bug. New programs need not use this macro.
If stdbool.h exists and conforms to C99 or later, define
HAVE_STDBOOL_H to 1; if the type _Bool is defined, define
HAVE__BOOL to 1.
This macro is obsolescent, as all current C compilers have
stdbool.h, a header that is itself obsolescent as of C23.
Nowadays programs that need bool, true and false
can include stdbool.h unconditionally, without using
AC_HEADER_STDBOOL, and if such a program needs to be portable
only to C23 or later it need not even include stdbool.h.
This macro caches its result in the ac_cv_header_stdbool_h
variable.
This macro differs from AC_CHECK_HEADER_STDBOOL only in that it
defines HAVE_STDBOOL_H whereas AC_CHECK_HEADER_STDBOOL
does not.
This macro is obsolescent. Its sole effect is to make sure that all the
headers that are included by AC_INCLUDES_DEFAULT (see Default Includes), but not part of C89, have been checked for.
All hosted environments that are still of interest for portable code provide all of the headers specified in C89 (as amended in 1995).
If sys/wait.h exists and is compatible with Posix, 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 compatible, then instead of including it, define the
Posix macros with their usual interpretations. Here is an
example:
#include <sys/types.h> #ifdef HAVE_SYS_WAIT_H # include <sys/wait.h> #endif #ifndef WEXITSTATUS # define WEXITSTATUS(stat_val) ((unsigned int) (stat_val) >> 8) #endif #ifndef WIFEXITED # define WIFEXITED(stat_val) (((stat_val) & 255) == 0) #endif
This macro caches its result in the ac_cv_header_sys_wait_h
variable.
This macro is obsolescent, as current systems are compatible with Posix. New programs need not use this macro.
_POSIX_VERSION is defined when unistd.h is included on
Posix systems. If there is no unistd.h, it is definitely
not a Posix system. However, some non-Posix systems do
have unistd.h.
The way to check whether the system supports Posix is:
#ifdef HAVE_UNISTD_H # include <sys/types.h> # include <unistd.h> #endif #ifdef _POSIX_VERSION /* Code for Posix systems. */ #endif
If the use of TIOCGWINSZ requires <sys/ioctl.h>, then
define GWINSZ_IN_SYS_IOCTL. Otherwise TIOCGWINSZ can be
found in <termios.h>.
Use:
#ifdef HAVE_TERMIOS_H # include <termios.h> #endif #ifdef GWINSZ_IN_SYS_IOCTL # include <sys/ioctl.h> #endif