78 lines
2.6 KiB
Text
78 lines
2.6 KiB
Text
# nullptr.m4
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# serial 2
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dnl Copyright 2023-2024 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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# Check for nullptr that conforms to C23 and C++11.
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AC_DEFUN([gl_NULLPTR],
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[
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m4_provide_if([AC_PROG_CC],
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[AC_LANG_PUSH([C])
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AC_CACHE_CHECK([for C nullptr], [gl_cv_c_nullptr],
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[AC_COMPILE_IFELSE(
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[AC_LANG_SOURCE([[int *p = nullptr;]])],
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[gl_cv_c_nullptr=yes
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# Work around <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114780>.
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gl_saved_CFLAGS=$CFLAGS
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CFLAGS="$CFLAGS -Wall -Werror"
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AC_COMPILE_IFELSE(
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[AC_LANG_PROGRAM(
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[[void f (char const *, ...) __attribute__ ((sentinel));]],
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[[f ("", nullptr);]])],
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[],
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[AC_COMPILE_IFELSE(
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[AC_LANG_PROGRAM(
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[[void f (char const *, ...) __attribute__ ((sentinel));]],
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[[f ("", (void *) 0);]])],
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[gl_cv_c_nullptr='not as a sentinel'])])
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CFLAGS=$gl_saved_CFLAGS],
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[gl_cv_c_nullptr=no])])
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gl_c_nullptr=$gl_cv_c_nullptr
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AC_LANG_POP([C])],
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[gl_c_nullptr=no])
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if test "$gl_c_nullptr" = yes; then
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AC_DEFINE([HAVE_C_NULLPTR], [1],
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[Define to 1 if C nullptr is known to work.])
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fi
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m4_provide_if([AC_PROG_CXX],
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[AC_LANG_PUSH([C++])
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AC_CACHE_CHECK([for C++ nullptr], [gl_cv_cxx_nullptr],
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[AC_COMPILE_IFELSE(
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[AC_LANG_SOURCE([[int *p = nullptr;]])],
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[gl_cv_cxx_nullptr=yes],
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[AC_COMPILE_IFELSE(
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[AC_LANG_SOURCE([[#include <stddef.h>
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int *p = nullptr;]])],
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[gl_cv_cxx_nullptr="yes, but it is a <stddef.h> macro"],
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[gl_cv_cxx_nullptr=no])])])
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AS_CASE([$gl_cv_cxx_nullptr],
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[yes], [gl_have_cxx_nullptr=1],
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[yes*], [gl_have_cxx_nullptr="(-1)"],
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[gl_have_cxx_nullptr=0])
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AC_DEFINE_UNQUOTED([HAVE_CXX_NULLPTR], [$gl_have_cxx_nullptr],
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[Define to 1 if C++ nullptr works, 0 if not,
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(-1) if it is a <stddef.h> macro.])
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AC_LANG_POP([C++])])
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])
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AH_VERBATIM([zznullptr],
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[#if defined __cplusplus && HAVE_CXX_NULLPTR < 0
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# include <stddef.h>
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# undef/**/nullptr
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#endif
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#ifndef nullptr
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# if !defined __cplusplus && !defined HAVE_C_NULLPTR
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# define nullptr ((void *) 0)
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# elif defined __cplusplus && HAVE_CXX_NULLPTR <= 0
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# if 3 <= __GNUG__
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# define nullptr __null
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# else
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# define nullptr 0L
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# endif
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# endif
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#endif])
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])
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