1# stddef_h.m4 serial 12 2dnl Copyright (C) 2009-2022 Free Software Foundation, Inc. 3dnl This file is free software; the Free Software Foundation 4dnl gives unlimited permission to copy and/or distribute it, 5dnl with or without modifications, as long as this notice is preserved. 6 7dnl A placeholder for <stddef.h>, for platforms that have issues. 8 9AC_DEFUN_ONCE([gl_STDDEF_H], 10[ 11 AC_REQUIRE([gl_STDDEF_H_DEFAULTS]) 12 AC_REQUIRE([gt_TYPE_WCHAR_T]) 13 14 dnl Persuade OpenBSD <stddef.h> to declare max_align_t. 15 AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS]) 16 17 GL_GENERATE_STDDEF_H=false 18 19 dnl Test whether the type max_align_t exists and whether its alignment 20 dnl "is as great as is supported by the implementation in all contexts". 21 AC_CACHE_CHECK([for good max_align_t], 22 [gl_cv_type_max_align_t], 23 [AC_COMPILE_IFELSE( 24 [AC_LANG_PROGRAM( 25 [[#include <stddef.h> 26 unsigned int s = sizeof (max_align_t); 27 #if defined __GNUC__ || defined __clang__ || defined __IBM__ALIGNOF__ 28 int check1[2 * (__alignof__ (double) <= __alignof__ (max_align_t)) - 1]; 29 int check2[2 * (__alignof__ (long double) <= __alignof__ (max_align_t)) - 1]; 30 #endif 31 typedef struct { char a; max_align_t b; } max_helper; 32 typedef struct { char a; long b; } long_helper; 33 typedef struct { char a; double b; } double_helper; 34 typedef struct { char a; long double b; } long_double_helper; 35 int check3[2 * (offsetof (long_helper, b) <= offsetof (max_helper, b)) - 1]; 36 int check4[2 * (offsetof (double_helper, b) <= offsetof (max_helper, b)) - 1]; 37 int check5[2 * (offsetof (long_double_helper, b) <= offsetof (max_helper, b)) - 1]; 38 ]])], 39 [gl_cv_type_max_align_t=yes], 40 [gl_cv_type_max_align_t=no]) 41 ]) 42 if test $gl_cv_type_max_align_t = no; then 43 HAVE_MAX_ALIGN_T=0 44 GL_GENERATE_STDDEF_H=true 45 fi 46 47 if test $gt_cv_c_wchar_t = no; then 48 HAVE_WCHAR_T=0 49 GL_GENERATE_STDDEF_H=true 50 fi 51 52 AC_CACHE_CHECK([whether NULL can be used in arbitrary expressions], 53 [gl_cv_decl_null_works], 54 [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <stddef.h> 55 int test[2 * (sizeof NULL == sizeof (void *)) -1]; 56]])], 57 [gl_cv_decl_null_works=yes], 58 [gl_cv_decl_null_works=no])]) 59 if test $gl_cv_decl_null_works = no; then 60 REPLACE_NULL=1 61 GL_GENERATE_STDDEF_H=true 62 fi 63 64 if $GL_GENERATE_STDDEF_H; then 65 gl_NEXT_HEADERS([stddef.h]) 66 fi 67]) 68 69# gl_STDDEF_MODULE_INDICATOR([modulename]) 70# sets the shell variable that indicates the presence of the given module 71# to a C preprocessor expression that will evaluate to 1. 72# This macro invocation must not occur in macros that are AC_REQUIREd. 73AC_DEFUN([gl_STDDEF_MODULE_INDICATOR], 74[ 75 dnl Ensure to expand the default settings once only. 76 gl_STDDEF_H_REQUIRE_DEFAULTS 77 gl_MODULE_INDICATOR_SET_VARIABLE([$1]) 78]) 79 80# Initializes the default values for AC_SUBSTed shell variables. 81# This macro must not be AC_REQUIREd. It must only be invoked, and only 82# outside of macros or in macros that are not AC_REQUIREd. 83AC_DEFUN([gl_STDDEF_H_REQUIRE_DEFAULTS], 84[ 85 m4_defun(GL_MODULE_INDICATOR_PREFIX[_STDDEF_H_MODULE_INDICATOR_DEFAULTS], [ 86 ]) 87 m4_require(GL_MODULE_INDICATOR_PREFIX[_STDDEF_H_MODULE_INDICATOR_DEFAULTS]) 88 AC_REQUIRE([gl_STDDEF_H_DEFAULTS]) 89]) 90 91AC_DEFUN([gl_STDDEF_H_DEFAULTS], 92[ 93 dnl Assume proper GNU behavior unless another module says otherwise. 94 REPLACE_NULL=0; AC_SUBST([REPLACE_NULL]) 95 HAVE_MAX_ALIGN_T=1; AC_SUBST([HAVE_MAX_ALIGN_T]) 96 HAVE_WCHAR_T=1; AC_SUBST([HAVE_WCHAR_T]) 97]) 98