1 # 00gnulib.m4 serial 8 2 dnl Copyright (C) 2009-2022 Free Software Foundation, Inc. 3 dnl This file is free software; the Free Software Foundation 4 dnl gives unlimited permission to copy and/or distribute it, 5 dnl with or without modifications, as long as this notice is preserved. 6 7 dnl This file must be named something that sorts before all other 8 dnl gnulib-provided .m4 files. It is needed until the clang fix has 9 dnl been included in Autoconf. 10 11 # The following definitions arrange to use a compiler option 12 # -Werror=implicit-function-declaration in AC_CHECK_DECL, when the 13 # compiler is clang. Without it, clang implicitly declares "known" 14 # library functions in C mode, but not in C++ mode, which would cause 15 # Gnulib to omit a declaration and thus later produce an error in C++ 16 # mode. As of clang 9.0, these "known" functions are identified through 17 # LIBBUILTIN invocations in the LLVM source file 18 # llvm/tools/clang/include/clang/Basic/Builtins.def. 19 # It's not possible to AC_REQUIRE the extra tests from AC_CHECK_DECL, 20 # because AC_CHECK_DECL, like other Autoconf built-ins, is not supposed 21 # to AC_REQUIRE anything: some configure.ac files have their first 22 # AC_CHECK_DECL executed conditionally. Therefore append the extra tests 23 # to AC_PROG_CC. 24 AC_DEFUN([gl_COMPILER_CLANG], 25 [ 26 dnl AC_REQUIRE([AC_PROG_CC]) 27 AC_CACHE_CHECK([whether the compiler is clang], 28 [gl_cv_compiler_clang], 29 [dnl Use _AC_COMPILE_IFELSE instead of AC_EGREP_CPP, to avoid error 30 dnl "circular dependency of AC_LANG_COMPILER(C)" if AC_PROG_CC has 31 dnl not yet been invoked. 32 _AC_COMPILE_IFELSE( 33 [AC_LANG_PROGRAM([[ 34 #ifdef __clang__ 35 barfbarf 36 #endif 37 ]],[[]]) 38 ], 39 [gl_cv_compiler_clang=no], 40 [gl_cv_compiler_clang=yes]) 41 ]) 42 ]) 43 AC_DEFUN([gl_COMPILER_PREPARE_CHECK_DECL], 44 [ 45 dnl AC_REQUIRE([AC_PROG_CC]) 46 dnl AC_REQUIRE([gl_COMPILER_CLANG]) 47 AC_CACHE_CHECK([for compiler option needed when checking for declarations], 48 [gl_cv_compiler_check_decl_option], 49 [if test $gl_cv_compiler_clang = yes; then 50 dnl Test whether the compiler supports the option 51 dnl '-Werror=implicit-function-declaration'. 52 save_ac_compile="$ac_compile" 53 ac_compile="$ac_compile -Werror=implicit-function-declaration" 54 dnl Use _AC_COMPILE_IFELSE instead of AC_COMPILE_IFELSE, to avoid a 55 dnl warning "AC_COMPILE_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS". 56 _AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]],[[]])], 57 [gl_cv_compiler_check_decl_option='-Werror=implicit-function-declaration'], 58 [gl_cv_compiler_check_decl_option=none]) 59 ac_compile="$save_ac_compile" 60 else 61 gl_cv_compiler_check_decl_option=none 62 fi 63 ]) 64 if test "x$gl_cv_compiler_check_decl_option" != xnone; then 65 ac_compile_for_check_decl="$ac_compile $gl_cv_compiler_check_decl_option" 66 else 67 ac_compile_for_check_decl="$ac_compile" 68 fi 69 ]) 70 dnl Redefine _AC_CHECK_DECL_BODY so that it references ac_compile_for_check_decl 71 dnl instead of ac_compile. If, for whatever reason, the override of AC_PROG_CC 72 dnl in zzgnulib.m4 is inactive, use the original ac_compile. 73 m4_define([_AC_CHECK_DECL_BODY], 74 [ ac_save_ac_compile="$ac_compile" 75 if test -n "$ac_compile_for_check_decl"; then 76 ac_compile="$ac_compile_for_check_decl" 77 fi] 78 m4_defn([_AC_CHECK_DECL_BODY])[ ac_compile="$ac_save_ac_compile" 79 ]) 80 81 # gl_00GNULIB 82 # ----------- 83 # Witness macro that this file has been included. Needed to force 84 # Automake to include this file prior to all other gnulib .m4 files. 85 AC_DEFUN([gl_00GNULIB]) 86
Indexes created Thu Apr 23 00:23:13 UTC 2026