gnulib/import/m4/stddef_h.m4

   1 dnl A placeholder for <stddef.h>, for platforms that have issues.
   2 # stddef_h.m4 serial 6
   3 dnl Copyright (C) 2009-2019 Free Software Foundation, Inc.
   4 dnl This file is free software; the Free Software Foundation
   5 dnl gives unlimited permission to copy and/or distribute it,
   6 dnl with or without modifications, as long as this notice is preserved.
   7
   8 AC_DEFUN([gl_STDDEF_H],
   9 [
  10   AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
  11   AC_REQUIRE([gt_TYPE_WCHAR_T])
  12   STDDEF_H=
  13
  14   dnl Test whether the type max_align_t exists and whether its alignment
  15   dnl "is as great as is supported by the implementation in all contexts".
  16   AC_CACHE_CHECK([for good max_align_t],
  17     [gl_cv_type_max_align_t],
  18     [AC_COMPILE_IFELSE(
  19        [AC_LANG_PROGRAM(
  20           [[#include <stddef.h>
  21             unsigned int s = sizeof (max_align_t);
  22             #if defined __GNUC__ || defined __IBM__ALIGNOF__
  23             int check1[2 * (__alignof__ (double) <= __alignof__ (max_align_t)) - 1];
  24             int check2[2 * (__alignof__ (long double) <= __alignof__ (max_align_t)) - 1];
  25             #endif
  26           ]])],
  27        [gl_cv_type_max_align_t=yes],
  28        [gl_cv_type_max_align_t=no])
  29     ])
  30   if test $gl_cv_type_max_align_t = no; then
  31     HAVE_MAX_ALIGN_T=0
  32     STDDEF_H=stddef.h
  33   fi
  34
  35   if test $gt_cv_c_wchar_t = no; then
  36     HAVE_WCHAR_T=0
  37     STDDEF_H=stddef.h
  38   fi
  39
  40   AC_CACHE_CHECK([whether NULL can be used in arbitrary expressions],
  41     [gl_cv_decl_null_works],
  42     [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <stddef.h>
  43       int test[2 * (sizeof NULL == sizeof (void *)) -1];
  44 ]])],
  45       [gl_cv_decl_null_works=yes],
  46       [gl_cv_decl_null_works=no])])
  47   if test $gl_cv_decl_null_works = no; then
  48     REPLACE_NULL=1
  49     STDDEF_H=stddef.h
  50   fi
  51
  52   AC_SUBST([STDDEF_H])
  53   AM_CONDITIONAL([GL_GENERATE_STDDEF_H], [test -n "$STDDEF_H"])
  54   if test -n "$STDDEF_H"; then
  55     gl_NEXT_HEADERS([stddef.h])
  56   fi
  57 ])
  58
  59 AC_DEFUN([gl_STDDEF_MODULE_INDICATOR],
  60 [
  61   dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
  62   AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
  63   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
  64 ])
  65
  66 AC_DEFUN([gl_STDDEF_H_DEFAULTS],
  67 [
  68   dnl Assume proper GNU behavior unless another module says otherwise.
  69   REPLACE_NULL=0;                AC_SUBST([REPLACE_NULL])
  70   HAVE_MAX_ALIGN_T=1;            AC_SUBST([HAVE_MAX_ALIGN_T])
  71   HAVE_WCHAR_T=1;                AC_SUBST([HAVE_WCHAR_T])
  72 ])