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Diffstat (limited to '')
| -rw-r--r-- | m4/00gnulib.m4 | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/m4/00gnulib.m4 b/m4/00gnulib.m4 new file mode 100644 index 0000000..7fe03e0 --- /dev/null +++ b/m4/00gnulib.m4 @@ -0,0 +1,85 @@ +# 00gnulib.m4 serial 8 +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 This file must be named something that sorts before all other +dnl gnulib-provided .m4 files. It is needed until the clang fix has +dnl been included in Autoconf. + +# The following definitions arrange to use a compiler option +# -Werror=implicit-function-declaration in AC_CHECK_DECL, when the +# compiler is clang. Without it, clang implicitly declares "known" +# library functions in C mode, but not in C++ mode, which would cause +# Gnulib to omit a declaration and thus later produce an error in C++ +# mode. As of clang 9.0, these "known" functions are identified through +# LIBBUILTIN invocations in the LLVM source file +# llvm/tools/clang/include/clang/Basic/Builtins.def. +# It's not possible to AC_REQUIRE the extra tests from AC_CHECK_DECL, +# because AC_CHECK_DECL, like other Autoconf built-ins, is not supposed +# to AC_REQUIRE anything: some configure.ac files have their first +# AC_CHECK_DECL executed conditionally. Therefore append the extra tests +# to AC_PROG_CC. +AC_DEFUN([gl_COMPILER_CLANG], +[ +dnl AC_REQUIRE([AC_PROG_CC]) + AC_CACHE_CHECK([whether the compiler is clang], + [gl_cv_compiler_clang], + [dnl Use _AC_COMPILE_IFELSE instead of AC_EGREP_CPP, to avoid error + dnl "circular dependency of AC_LANG_COMPILER(C)" if AC_PROG_CC has + dnl not yet been invoked. + _AC_COMPILE_IFELSE( + [AC_LANG_PROGRAM([[ + #ifdef __clang__ + barfbarf + #endif + ]],[[]]) + ], + [gl_cv_compiler_clang=no], + [gl_cv_compiler_clang=yes]) + ]) +]) +AC_DEFUN([gl_COMPILER_PREPARE_CHECK_DECL], +[ +dnl AC_REQUIRE([AC_PROG_CC]) +dnl AC_REQUIRE([gl_COMPILER_CLANG]) + AC_CACHE_CHECK([for compiler option needed when checking for declarations], + [gl_cv_compiler_check_decl_option], + [if test $gl_cv_compiler_clang = yes; then + dnl Test whether the compiler supports the option + dnl '-Werror=implicit-function-declaration'. + save_ac_compile="$ac_compile" + ac_compile="$ac_compile -Werror=implicit-function-declaration" + dnl Use _AC_COMPILE_IFELSE instead of AC_COMPILE_IFELSE, to avoid a + dnl warning "AC_COMPILE_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS". + _AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]],[[]])], + [gl_cv_compiler_check_decl_option='-Werror=implicit-function-declaration'], + [gl_cv_compiler_check_decl_option=none]) + ac_compile="$save_ac_compile" + else + gl_cv_compiler_check_decl_option=none + fi + ]) + if test "x$gl_cv_compiler_check_decl_option" != xnone; then + ac_compile_for_check_decl="$ac_compile $gl_cv_compiler_check_decl_option" + else + ac_compile_for_check_decl="$ac_compile" + fi +]) +dnl Redefine _AC_CHECK_DECL_BODY so that it references ac_compile_for_check_decl +dnl instead of ac_compile. If, for whatever reason, the override of AC_PROG_CC +dnl in zzgnulib.m4 is inactive, use the original ac_compile. +m4_define([_AC_CHECK_DECL_BODY], +[ ac_save_ac_compile="$ac_compile" + if test -n "$ac_compile_for_check_decl"; then + ac_compile="$ac_compile_for_check_decl" + fi] +m4_defn([_AC_CHECK_DECL_BODY])[ ac_compile="$ac_save_ac_compile" +]) + +# gl_00GNULIB +# ----------- +# Witness macro that this file has been included. Needed to force +# Automake to include this file prior to all other gnulib .m4 files. +AC_DEFUN([gl_00GNULIB]) |