104 lines
4 KiB
Text
104 lines
4 KiB
Text
# stddef_h.m4 serial 13
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dnl Copyright (C) 2009-2023 Free Software Foundation, Inc.
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dnl This file is free software; the Free Software Foundation
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dnl gives unlimited permission to copy and/or distribute it,
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dnl with or without modifications, as long as this notice is preserved.
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dnl A placeholder for <stddef.h>, for platforms that have issues.
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AC_DEFUN_ONCE([gl_STDDEF_H],
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[
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AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
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AC_REQUIRE([gt_TYPE_WCHAR_T])
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dnl Persuade OpenBSD <stddef.h> to declare max_align_t.
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AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
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GL_GENERATE_STDDEF_H=false
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dnl Test whether the type max_align_t exists and whether its alignment
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dnl "is as great as is supported by the implementation in all contexts".
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AC_CACHE_CHECK([for good max_align_t],
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[gl_cv_type_max_align_t],
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[AC_COMPILE_IFELSE(
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[AC_LANG_PROGRAM(
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[[/* On FreeBSD 12.0/x86, max_align_t defined by <stddef.h> has
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the correct alignment with the default (wrong) definition of
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_Alignof, but a wrong alignment as soon as we activate an
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ISO C compliant _Alignof definition. */
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#if ((defined __GNUC__ && 4 <= __GNUC__) || defined __clang__) && !defined __cplusplus
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#define _Alignof(type) __builtin_offsetof (struct { char __a; type __b; }, __b)
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#endif
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#include <stddef.h>
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unsigned int s = sizeof (max_align_t);
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#if defined __GNUC__ || defined __clang__ || defined __IBM__ALIGNOF__
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int check1[2 * (__alignof__ (double) <= __alignof__ (max_align_t)) - 1];
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int check2[2 * (__alignof__ (long double) <= __alignof__ (max_align_t)) - 1];
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#endif
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typedef struct { char a; max_align_t b; } max_helper;
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typedef struct { char a; long b; } long_helper;
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typedef struct { char a; double b; } double_helper;
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typedef struct { char a; long double b; } long_double_helper;
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int check3[2 * (offsetof (long_helper, b) <= offsetof (max_helper, b)) - 1];
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int check4[2 * (offsetof (double_helper, b) <= offsetof (max_helper, b)) - 1];
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int check5[2 * (offsetof (long_double_helper, b) <= offsetof (max_helper, b)) - 1];
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]])],
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[gl_cv_type_max_align_t=yes],
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[gl_cv_type_max_align_t=no])
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])
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if test $gl_cv_type_max_align_t = no; then
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HAVE_MAX_ALIGN_T=0
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GL_GENERATE_STDDEF_H=true
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fi
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if test $gt_cv_c_wchar_t = no; then
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HAVE_WCHAR_T=0
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GL_GENERATE_STDDEF_H=true
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fi
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AC_CACHE_CHECK([whether NULL can be used in arbitrary expressions],
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[gl_cv_decl_null_works],
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[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <stddef.h>
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int test[2 * (sizeof NULL == sizeof (void *)) -1];
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]])],
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[gl_cv_decl_null_works=yes],
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[gl_cv_decl_null_works=no])])
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if test $gl_cv_decl_null_works = no; then
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REPLACE_NULL=1
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GL_GENERATE_STDDEF_H=true
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fi
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if $GL_GENERATE_STDDEF_H; then
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gl_NEXT_HEADERS([stddef.h])
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fi
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])
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# gl_STDDEF_MODULE_INDICATOR([modulename])
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# sets the shell variable that indicates the presence of the given module
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# to a C preprocessor expression that will evaluate to 1.
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# This macro invocation must not occur in macros that are AC_REQUIREd.
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AC_DEFUN([gl_STDDEF_MODULE_INDICATOR],
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[
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dnl Ensure to expand the default settings once only.
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gl_STDDEF_H_REQUIRE_DEFAULTS
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gl_MODULE_INDICATOR_SET_VARIABLE([$1])
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])
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# Initializes the default values for AC_SUBSTed shell variables.
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# This macro must not be AC_REQUIREd. It must only be invoked, and only
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# outside of macros or in macros that are not AC_REQUIREd.
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AC_DEFUN([gl_STDDEF_H_REQUIRE_DEFAULTS],
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[
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m4_defun(GL_MODULE_INDICATOR_PREFIX[_STDDEF_H_MODULE_INDICATOR_DEFAULTS], [
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])
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m4_require(GL_MODULE_INDICATOR_PREFIX[_STDDEF_H_MODULE_INDICATOR_DEFAULTS])
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AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
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])
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AC_DEFUN([gl_STDDEF_H_DEFAULTS],
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[
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dnl Assume proper GNU behavior unless another module says otherwise.
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REPLACE_NULL=0; AC_SUBST([REPLACE_NULL])
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HAVE_MAX_ALIGN_T=1; AC_SUBST([HAVE_MAX_ALIGN_T])
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HAVE_WCHAR_T=1; AC_SUBST([HAVE_WCHAR_T])
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])
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