diff options
Diffstat (limited to 'm4/00gnulib.m4')
| -rw-r--r-- | m4/00gnulib.m4 | 79 |
1 files changed, 75 insertions, 4 deletions
diff --git a/m4/00gnulib.m4 b/m4/00gnulib.m4 index 1a1a1d74f7e..06eff4f3863 100644 --- a/m4/00gnulib.m4 +++ b/m4/00gnulib.m4 @@ -1,13 +1,14 @@ -# 00gnulib.m4 serial 3 +# 00gnulib.m4 serial 7 dnl Copyright (C) 2009-2020 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 such time as we can -dnl assume Autoconf 2.64, with its improved AC_DEFUN_ONCE and -dnl m4_divert semantics. +dnl gnulib-provided .m4 files. The first part is needed until such time +dnl as we can assume Autoconf 2.64, with its improved AC_DEFUN_ONCE and +dnl m4_divert semantics. The second part is needed until the clang fix +dnl has been included in Autoconf. # Until autoconf 2.63, handling of the diversion stack required m4_init # to be called first; but this does not happen with aclocal. Wrapping @@ -39,6 +40,76 @@ m4_version_prereq([2.63.263], [], [m4_indir([_gl_DEFUN_ONCE([$1])])])])]dnl [AC][_DEFUN([_gl_DEFUN_ONCE([$1])], [$2])])]) +# 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 |