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Diffstat (limited to 'm4/stddef_h.m4')
| -rw-r--r-- | m4/stddef_h.m4 | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/m4/stddef_h.m4 b/m4/stddef_h.m4 new file mode 100644 index 0000000..aa01221 --- /dev/null +++ b/m4/stddef_h.m4 @@ -0,0 +1,119 @@ +# stddef_h.m4 serial 14 +dnl Copyright (C) 2009-2023 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. + +dnl A placeholder for <stddef.h>, for platforms that have issues. + +AC_DEFUN_ONCE([gl_STDDEF_H], +[ + AC_REQUIRE([gl_STDDEF_H_DEFAULTS]) + AC_REQUIRE([gt_TYPE_WCHAR_T]) + + dnl Persuade OpenBSD <stddef.h> to declare max_align_t. + AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS]) + + GL_GENERATE_STDDEF_H=false + + dnl Test whether the type max_align_t exists and whether its alignment + dnl "is as great as is supported by the implementation in all contexts". + AC_CACHE_CHECK([for good max_align_t], + [gl_cv_type_max_align_t], + [AC_COMPILE_IFELSE( + [AC_LANG_PROGRAM( + [[/* On FreeBSD 12.0/x86, max_align_t defined by <stddef.h> has + the correct alignment with the default (wrong) definition of + _Alignof, but a wrong alignment as soon as we activate an + ISO C compliant _Alignof definition. */ + #if ((defined __GNUC__ && 4 <= __GNUC__) || defined __clang__) && !defined __cplusplus + #define _Alignof(type) __builtin_offsetof (struct { char __a; type __b; }, __b) + #endif + #include <stddef.h> + unsigned int s = sizeof (max_align_t); + #if defined __GNUC__ || defined __clang__ || defined __IBM__ALIGNOF__ + int check1[2 * (__alignof__ (double) <= __alignof__ (max_align_t)) - 1]; + int check2[2 * (__alignof__ (long double) <= __alignof__ (max_align_t)) - 1]; + #endif + typedef struct { char a; max_align_t b; } max_helper; + typedef struct { char a; long b; } long_helper; + typedef struct { char a; double b; } double_helper; + typedef struct { char a; long double b; } long_double_helper; + int check3[2 * (offsetof (long_helper, b) <= offsetof (max_helper, b)) - 1]; + int check4[2 * (offsetof (double_helper, b) <= offsetof (max_helper, b)) - 1]; + int check5[2 * (offsetof (long_double_helper, b) <= offsetof (max_helper, b)) - 1]; + ]])], + [gl_cv_type_max_align_t=yes], + [gl_cv_type_max_align_t=no]) + ]) + if test $gl_cv_type_max_align_t = no; then + HAVE_MAX_ALIGN_T=0 + GL_GENERATE_STDDEF_H=true + fi + + if test $gt_cv_c_wchar_t = no; then + HAVE_WCHAR_T=0 + GL_GENERATE_STDDEF_H=true + fi + + AC_CACHE_CHECK([whether NULL can be used in arbitrary expressions], + [gl_cv_decl_null_works], + [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <stddef.h> + int test[2 * (sizeof NULL == sizeof (void *)) -1]; +]])], + [gl_cv_decl_null_works=yes], + [gl_cv_decl_null_works=no])]) + if test $gl_cv_decl_null_works = no; then + REPLACE_NULL=1 + GL_GENERATE_STDDEF_H=true + fi + + AC_CACHE_CHECK([for unreachable], + [gl_cv_func_unreachable], + [AC_LINK_IFELSE( + [AC_LANG_PROGRAM( + [[#include <stddef.h> + ]], + [[unreachable (); + ]])], + [gl_cv_func_unreachable=yes], + [gl_cv_func_unreachable=no]) + ]) + if test $gl_cv_func_unreachable = no; then + GL_GENERATE_STDDEF_H=true + fi + + if $GL_GENERATE_STDDEF_H; then + gl_NEXT_HEADERS([stddef.h]) + fi +]) + +# gl_STDDEF_MODULE_INDICATOR([modulename]) +# sets the shell variable that indicates the presence of the given module +# to a C preprocessor expression that will evaluate to 1. +# This macro invocation must not occur in macros that are AC_REQUIREd. +AC_DEFUN([gl_STDDEF_MODULE_INDICATOR], +[ + dnl Ensure to expand the default settings once only. + gl_STDDEF_H_REQUIRE_DEFAULTS + gl_MODULE_INDICATOR_SET_VARIABLE([$1]) +]) + +# Initializes the default values for AC_SUBSTed shell variables. +# This macro must not be AC_REQUIREd. It must only be invoked, and only +# outside of macros or in macros that are not AC_REQUIREd. +AC_DEFUN([gl_STDDEF_H_REQUIRE_DEFAULTS], +[ + m4_defun(GL_MODULE_INDICATOR_PREFIX[_STDDEF_H_MODULE_INDICATOR_DEFAULTS], [ + ]) + m4_require(GL_MODULE_INDICATOR_PREFIX[_STDDEF_H_MODULE_INDICATOR_DEFAULTS]) + AC_REQUIRE([gl_STDDEF_H_DEFAULTS]) +]) + +AC_DEFUN([gl_STDDEF_H_DEFAULTS], +[ + dnl Assume proper GNU behavior unless another module says otherwise. + REPLACE_NULL=0; AC_SUBST([REPLACE_NULL]) + HAVE_MAX_ALIGN_T=1; AC_SUBST([HAVE_MAX_ALIGN_T]) + HAVE_WCHAR_T=1; AC_SUBST([HAVE_WCHAR_T]) +]) |