1# 00gnulib.m4 serial 7 2dnl Copyright (C) 2009-2020 Free Software Foundation, Inc. 3dnl This file is free software; the Free Software Foundation 4dnl gives unlimited permission to copy and/or distribute it, 5dnl with or without modifications, as long as this notice is preserved. 6 7dnl This file must be named something that sorts before all other 8dnl gnulib-provided .m4 files. The first part is needed until such time 9dnl as we can assume Autoconf 2.64, with its improved AC_DEFUN_ONCE and 10dnl m4_divert semantics. The second part is needed until the clang fix 11dnl has been included in Autoconf. 12 13# Until autoconf 2.63, handling of the diversion stack required m4_init 14# to be called first; but this does not happen with aclocal. Wrapping 15# the entire execution in another layer of the diversion stack fixes this. 16# Worse, prior to autoconf 2.62, m4_wrap depended on the underlying m4 17# for whether it was FIFO or LIFO; in order to properly balance with 18# m4_init, we need to undo our push just before anything wrapped within 19# the m4_init body. The way to ensure this is to wrap both sides of 20# m4_init with a one-shot macro that does the pop at the right time. 21m4_ifndef([_m4_divert_diversion], 22[m4_divert_push([KILL]) 23m4_define([gl_divert_fixup], [m4_divert_pop()m4_define([$0])]) 24m4_define([m4_init], 25 [gl_divert_fixup()]m4_defn([m4_init])[gl_divert_fixup()])]) 26 27 28# AC_DEFUN_ONCE([NAME], VALUE) 29# ---------------------------- 30# Define NAME to expand to VALUE on the first use (whether by direct 31# expansion, or by AC_REQUIRE), and to nothing on all subsequent uses. 32# Avoid bugs in AC_REQUIRE in Autoconf 2.63 and earlier. This 33# definition is slower than the version in Autoconf 2.64, because it 34# can only use interfaces that existed since 2.59; but it achieves the 35# same effect. Quoting is necessary to avoid confusing Automake. 36m4_version_prereq([2.63.263], [], 37[m4_define([AC][_DEFUN_ONCE], 38 [AC][_DEFUN([$1], 39 [AC_REQUIRE([_gl_DEFUN_ONCE([$1])], 40 [m4_indir([_gl_DEFUN_ONCE([$1])])])])]dnl 41[AC][_DEFUN([_gl_DEFUN_ONCE([$1])], [$2])])]) 42 43# The following definitions arrange to use a compiler option 44# -Werror=implicit-function-declaration in AC_CHECK_DECL, when the 45# compiler is clang. Without it, clang implicitly declares "known" 46# library functions in C mode, but not in C++ mode, which would cause 47# Gnulib to omit a declaration and thus later produce an error in C++ 48# mode. As of clang 9.0, these "known" functions are identified through 49# LIBBUILTIN invocations in the LLVM source file 50# llvm/tools/clang/include/clang/Basic/Builtins.def. 51# It's not possible to AC_REQUIRE the extra tests from AC_CHECK_DECL, 52# because AC_CHECK_DECL, like other Autoconf built-ins, is not supposed 53# to AC_REQUIRE anything: some configure.ac files have their first 54# AC_CHECK_DECL executed conditionally. Therefore append the extra tests 55# to AC_PROG_CC. 56AC_DEFUN([gl_COMPILER_CLANG], 57[ 58dnl AC_REQUIRE([AC_PROG_CC]) 59 AC_CACHE_CHECK([whether the compiler is clang], 60 [gl_cv_compiler_clang], 61 [dnl Use _AC_COMPILE_IFELSE instead of AC_EGREP_CPP, to avoid error 62 dnl "circular dependency of AC_LANG_COMPILER(C)" if AC_PROG_CC has 63 dnl not yet been invoked. 64 _AC_COMPILE_IFELSE( 65 [AC_LANG_PROGRAM([[ 66 #ifdef __clang__ 67 barfbarf 68 #endif 69 ]],[[]]) 70 ], 71 [gl_cv_compiler_clang=no], 72 [gl_cv_compiler_clang=yes]) 73 ]) 74]) 75AC_DEFUN([gl_COMPILER_PREPARE_CHECK_DECL], 76[ 77dnl AC_REQUIRE([AC_PROG_CC]) 78dnl AC_REQUIRE([gl_COMPILER_CLANG]) 79 AC_CACHE_CHECK([for compiler option needed when checking for declarations], 80 [gl_cv_compiler_check_decl_option], 81 [if test $gl_cv_compiler_clang = yes; then 82 dnl Test whether the compiler supports the option 83 dnl '-Werror=implicit-function-declaration'. 84 save_ac_compile="$ac_compile" 85 ac_compile="$ac_compile -Werror=implicit-function-declaration" 86 dnl Use _AC_COMPILE_IFELSE instead of AC_COMPILE_IFELSE, to avoid a 87 dnl warning "AC_COMPILE_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS". 88 _AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]],[[]])], 89 [gl_cv_compiler_check_decl_option='-Werror=implicit-function-declaration'], 90 [gl_cv_compiler_check_decl_option=none]) 91 ac_compile="$save_ac_compile" 92 else 93 gl_cv_compiler_check_decl_option=none 94 fi 95 ]) 96 if test "x$gl_cv_compiler_check_decl_option" != xnone; then 97 ac_compile_for_check_decl="$ac_compile $gl_cv_compiler_check_decl_option" 98 else 99 ac_compile_for_check_decl="$ac_compile" 100 fi 101]) 102dnl Redefine _AC_CHECK_DECL_BODY so that it references ac_compile_for_check_decl 103dnl instead of ac_compile. If, for whatever reason, the override of AC_PROG_CC 104dnl in zzgnulib.m4 is inactive, use the original ac_compile. 105m4_define([_AC_CHECK_DECL_BODY], 106[ ac_save_ac_compile="$ac_compile" 107 if test -n "$ac_compile_for_check_decl"; then 108 ac_compile="$ac_compile_for_check_decl" 109 fi] 110m4_defn([_AC_CHECK_DECL_BODY])[ ac_compile="$ac_save_ac_compile" 111]) 112 113# gl_00GNULIB 114# ----------- 115# Witness macro that this file has been included. Needed to force 116# Automake to include this file prior to all other gnulib .m4 files. 117AC_DEFUN([gl_00GNULIB]) 118