# sys_select_h.m4 serial 20

dnl Copyright (C) 2006-2020 Free Software Foundation, Inc.

dnl This file is free software; the Free Software Foundation

dnl gives unlimited permission to copy and/or distribute it,

dnl with or without modifications, as long as this notice is preserved.

AC_DEFUN([gl_HEADER_SYS_SELECT],

[

  AC_REQUIRE([AC_C_RESTRICT])

  AC_REQUIRE([gl_SYS_SELECT_H_DEFAULTS])

  AC_CACHE_CHECK([whether <sys/select.h> is self-contained],

    [gl_cv_header_sys_select_h_selfcontained],

    [

      dnl Test against two bugs:

      dnl 1. On many platforms, <sys/select.h> assumes prior inclusion of

      dnl    <sys/types.h>.

      dnl 2. On OSF/1 4.0, <sys/select.h> provides only a forward declaration

      dnl    of 'struct timeval', and no definition of this type.

      AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <sys/select.h>]],

                                         [[struct timeval b;]])],

        [gl_cv_header_sys_select_h_selfcontained=yes],

        [gl_cv_header_sys_select_h_selfcontained=no])

      dnl Test against another bug:

      dnl 3. On Solaris 10, <sys/select.h> provides an FD_ZERO implementation

      dnl    that relies on memset(), but without including <string.h>.

      if test $gl_cv_header_sys_select_h_selfcontained = yes; then

        AC_COMPILE_IFELSE(

          [AC_LANG_PROGRAM([[#include <sys/select.h>]],

                           [[int memset; int bzero;]])

          ],

          [AC_LINK_IFELSE(

             [AC_LANG_PROGRAM([[#include <sys/select.h>]], [[

                  #undef memset

                  #define memset nonexistent_memset

                  extern

                  #ifdef __cplusplus

                  "C"

                  #endif

                  void *memset (void *, int, unsigned long);

                  #undef bzero

                  #define bzero nonexistent_bzero

                  extern

                  #ifdef __cplusplus

                  "C"

                  #endif

                  void bzero (void *, unsigned long);

                  fd_set fds;

                  FD_ZERO (&fds);

                ]])

             ],

             [],

             [gl_cv_header_sys_select_h_selfcontained=no])

          ])

      fi

    ])

  dnl <sys/select.h> is always overridden, because of GNULIB_POSIXCHECK.

  gl_CHECK_NEXT_HEADERS([sys/select.h])

  if test $ac_cv_header_sys_select_h = yes; then

    HAVE_SYS_SELECT_H=1

  else

    HAVE_SYS_SELECT_H=0

  fi

  AC_SUBST([HAVE_SYS_SELECT_H])

  gl_PREREQ_SYS_H_WINSOCK2

  dnl Check for declarations of anything we want to poison if the

  dnl corresponding gnulib module is not in use.

  gl_WARN_ON_USE_PREPARE([[

/* Some systems require prerequisite headers.  */

#include <sys/types.h>

#if !(defined __GLIBC__ && !defined __UCLIBC__) && HAVE_SYS_TIME_H

# include <sys/time.h>

#endif

#include <sys/select.h>

    ]], [pselect select])

])

AC_DEFUN([gl_SYS_SELECT_MODULE_INDICATOR],

[

  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.

  AC_REQUIRE([gl_SYS_SELECT_H_DEFAULTS])

  gl_MODULE_INDICATOR_SET_VARIABLE([$1])

  dnl Define it also as a C macro, for the benefit of the unit tests.

  gl_MODULE_INDICATOR_FOR_TESTS([$1])

])

AC_DEFUN([gl_SYS_SELECT_H_DEFAULTS],

[

  GNULIB_PSELECT=0; AC_SUBST([GNULIB_PSELECT])

  GNULIB_SELECT=0; AC_SUBST([GNULIB_SELECT])

  dnl Assume proper GNU behavior unless another module says otherwise.

  HAVE_PSELECT=1; AC_SUBST([HAVE_PSELECT])

  REPLACE_PSELECT=0; AC_SUBST([REPLACE_PSELECT])

  REPLACE_SELECT=0; AC_SUBST([REPLACE_SELECT])

])