| 1 | # stddef_h.m4 serial 11
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| 2 | dnl Copyright (C) 2009-2021 Free Software Foundation, Inc.
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| 3 | dnl This file is free software; the Free Software Foundation
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| 4 | dnl gives unlimited permission to copy and/or distribute it,
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| 5 | dnl with or without modifications, as long as this notice is preserved.
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| 6 |
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| 7 | dnl A placeholder for <stddef.h>, for platforms that have issues.
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| 8 |
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| 9 | AC_DEFUN_ONCE([gl_STDDEF_H],
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| 10 | [
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| 11 | AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
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| 12 | AC_REQUIRE([gt_TYPE_WCHAR_T])
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| 13 |
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| 14 | dnl Persuade OpenBSD <stddef.h> to declare max_align_t.
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| 15 | AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
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| 16 |
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| 17 | STDDEF_H=
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| 18 |
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| 19 | dnl Test whether the type max_align_t exists and whether its alignment
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| 20 | dnl "is as great as is supported by the implementation in all contexts".
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| 21 | AC_CACHE_CHECK([for good max_align_t],
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| 22 | [gl_cv_type_max_align_t],
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| 23 | [AC_COMPILE_IFELSE(
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| 24 | [AC_LANG_PROGRAM(
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| 25 | [[#include <stddef.h>
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| 26 | unsigned int s = sizeof (max_align_t);
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| 27 | #if defined __GNUC__ || defined __clang__ || defined __IBM__ALIGNOF__
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| 28 | int check1[2 * (__alignof__ (double) <= __alignof__ (max_align_t)) - 1];
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| 29 | int check2[2 * (__alignof__ (long double) <= __alignof__ (max_align_t)) - 1];
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| 30 | #endif
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| 31 | typedef struct { char a; max_align_t b; } max_helper;
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| 32 | typedef struct { char a; long b; } long_helper;
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| 33 | typedef struct { char a; double b; } double_helper;
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| 34 | typedef struct { char a; long double b; } long_double_helper;
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| 35 | int check3[2 * (offsetof (long_helper, b) <= offsetof (max_helper, b)) - 1];
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| 36 | int check4[2 * (offsetof (double_helper, b) <= offsetof (max_helper, b)) - 1];
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| 37 | int check5[2 * (offsetof (long_double_helper, b) <= offsetof (max_helper, b)) - 1];
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| 38 | ]])],
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| 39 | [gl_cv_type_max_align_t=yes],
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| 40 | [gl_cv_type_max_align_t=no])
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| 41 | ])
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| 42 | if test $gl_cv_type_max_align_t = no; then
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| 43 | HAVE_MAX_ALIGN_T=0
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| 44 | STDDEF_H=stddef.h
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| 45 | fi
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| 46 |
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| 47 | if test $gt_cv_c_wchar_t = no; then
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| 48 | HAVE_WCHAR_T=0
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| 49 | STDDEF_H=stddef.h
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| 50 | fi
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| 51 |
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| 52 | AC_CACHE_CHECK([whether NULL can be used in arbitrary expressions],
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| 53 | [gl_cv_decl_null_works],
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| 54 | [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <stddef.h>
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| 55 | int test[2 * (sizeof NULL == sizeof (void *)) -1];
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| 56 | ]])],
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| 57 | [gl_cv_decl_null_works=yes],
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| 58 | [gl_cv_decl_null_works=no])])
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| 59 | if test $gl_cv_decl_null_works = no; then
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| 60 | REPLACE_NULL=1
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| 61 | STDDEF_H=stddef.h
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| 62 | fi
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| 63 |
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| 64 | AC_SUBST([STDDEF_H])
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| 65 | AM_CONDITIONAL([GL_GENERATE_STDDEF_H], [test -n "$STDDEF_H"])
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| 66 | if test -n "$STDDEF_H"; then
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| 67 | gl_NEXT_HEADERS([stddef.h])
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| 68 | fi
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| 69 | ])
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| 70 |
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| 71 | # gl_STDDEF_MODULE_INDICATOR([modulename])
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| 72 | # sets the shell variable that indicates the presence of the given module
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| 73 | # to a C preprocessor expression that will evaluate to 1.
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| 74 | # This macro invocation must not occur in macros that are AC_REQUIREd.
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| 75 | AC_DEFUN([gl_STDDEF_MODULE_INDICATOR],
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| 76 | [
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| 77 | dnl Ensure to expand the default settings once only.
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| 78 | gl_STDDEF_H_REQUIRE_DEFAULTS
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| 79 | gl_MODULE_INDICATOR_SET_VARIABLE([$1])
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| 80 | ])
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| 81 |
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| 82 | # Initializes the default values for AC_SUBSTed shell variables.
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| 83 | # This macro must not be AC_REQUIREd. It must only be invoked, and only
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| 84 | # outside of macros or in macros that are not AC_REQUIREd.
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| 85 | AC_DEFUN([gl_STDDEF_H_REQUIRE_DEFAULTS],
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| 86 | [
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| 87 | m4_defun(GL_MODULE_INDICATOR_PREFIX[_STDDEF_H_MODULE_INDICATOR_DEFAULTS], [
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| 88 | ])
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| 89 | m4_require(GL_MODULE_INDICATOR_PREFIX[_STDDEF_H_MODULE_INDICATOR_DEFAULTS])
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| 90 | AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
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| 91 | ])
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| 92 |
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| 93 | AC_DEFUN([gl_STDDEF_H_DEFAULTS],
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| 94 | [
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| 95 | dnl Assume proper GNU behavior unless another module says otherwise.
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| 96 | REPLACE_NULL=0; AC_SUBST([REPLACE_NULL])
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| 97 | HAVE_MAX_ALIGN_T=1; AC_SUBST([HAVE_MAX_ALIGN_T])
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| 98 | HAVE_WCHAR_T=1; AC_SUBST([HAVE_WCHAR_T])
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| 99 | ])
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