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Diffstat (limited to 'config/check_decls.m4')
| -rw-r--r-- | config/check_decls.m4 | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/config/check_decls.m4 b/config/check_decls.m4 new file mode 100644 index 0000000000..2712daaedf --- /dev/null +++ b/config/check_decls.m4 @@ -0,0 +1,112 @@ +# config/check_decls.m4 + +# This file redefines the standard Autoconf macro AC_CHECK_DECL, +# and adds a supporting function _AC_UNDECLARED_WARNING, to make +# AC_CHECK_DECLS behave correctly when checking for built-in library +# functions with clang. + +# This is based on commit 82ef7805faffa151e724aa76c245ec590d174580 +# in the Autoconf git repository, adapted to work with Autoconf 2.63. +# It's still mostly their code, so +# it's distributed under Autoconf's license: + +# This file is part of Autoconf. This program is free +# software; you can redistribute it and/or modify it under the +# terms of the GNU General Public License as published by the +# Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# Under Section 7 of GPL version 3, you are granted additional +# permissions described in the Autoconf Configure Script Exception, +# version 3.0, as published by the Free Software Foundation. +# +# You should have received a copy of the GNU General Public License +# and a copy of the Autoconf Configure Script Exception along with +# this program; see the files COPYINGv3 and COPYING.EXCEPTION +# respectively. If not, see <http://www.gnu.org/licenses/>. + +# Written by David MacKenzie, with help from +# Franc,ois Pinard, Karl Berry, Richard Pixley, Ian Lance Taylor, +# Roland McGrath, Noah Friedman, david d zuhn, and many others. + + +# _AC_UNDECLARED_WARNING +# ---------------------- +# Set ac_[]_AC_LANG_ABBREV[]_decl_warn_flag=yes if the compiler uses a warning, +# not a more-customary error, to report some undeclared identifiers. Fail when +# an affected compiler warns also on valid input. _AC_PROG_PREPROC_WORKS_IFELSE +# solves a related problem. +AC_DEFUN([_AC_UNDECLARED_WARNING], +[# The Clang compiler raises a warning for an undeclared identifier that matches +# a compiler builtin function. All extant Clang versions are affected, as of +# Clang 3.6.0. Test a builtin known to every version. This problem affects the +# C and Objective C languages, but Clang does report an error under C++ and +# Objective C++. +# +# Passing -fno-builtin to the compiler would suppress this problem. That +# strategy would have the advantage of being insensitive to stray warnings, but +# it would make tests less realistic. +AC_CACHE_CHECK([how $CC reports undeclared, standard C functions], +[ac_cv_[]_AC_LANG_ABBREV[]_decl_report], +[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [(void) strchr;])], + [AS_IF([test -s conftest.err], [dnl + # For AC_CHECK_DECL to react to warnings, the compiler must be silent on + # valid AC_CHECK_DECL input. No library function is consistently available + # on freestanding implementations, so test against a dummy declaration. + # Include always-available headers on the off chance that they somehow + # elicit warnings. + AC_COMPILE_IFELSE([AC_LANG_PROGRAM([dnl +#include <float.h> +#include <limits.h> +#include <stdarg.h> +#include <stddef.h> +extern void ac_decl (int, char *);], +[@%:@ifdef __cplusplus + (void) ac_decl ((int) 0, (char *) 0); + (void) ac_decl; +@%:@else + (void) ac_decl; +@%:@endif +])], + [AS_IF([test -s conftest.err], + [AC_MSG_FAILURE([cannot detect from compiler exit status or warnings])], + [ac_cv_[]_AC_LANG_ABBREV[]_decl_report=warning])], + [AC_MSG_FAILURE([cannot compile a simple declaration test])])], + [AC_MSG_FAILURE([compiler does not report undeclared identifiers])])], + [ac_cv_[]_AC_LANG_ABBREV[]_decl_report=error])]) + +case $ac_cv_[]_AC_LANG_ABBREV[]_decl_report in + warning) ac_[]_AC_LANG_ABBREV[]_decl_warn_flag=yes ;; + *) ac_[]_AC_LANG_ABBREV[]_decl_warn_flag= ;; +esac +])# _AC_UNDECLARED_WARNING + +# AC_CHECK_DECL +# ------------- +# Replace Autoconf 2.63's standard definition of AC_CHECK_DECL, +# setting it up to treat warnings as errors if necessary. +m4_define([AC_CHECK_DECL], +[dnl Initialize each $ac_[]_AC_LANG_ABBREV[]_decl_warn_flag once. +AC_DEFUN([_AC_UNDECLARED_WARNING_]_AC_LANG_ABBREV, + [_AC_UNDECLARED_WARNING])dnl +AC_REQUIRE([_AC_UNDECLARED_WARNING_]_AC_LANG_ABBREV)dnl +AS_VAR_PUSHDEF([ac_Symbol], [ac_cv_have_decl_$1])dnl +AC_CACHE_CHECK([whether $1 is declared], [ac_Symbol], +[ac_save_werror_flag=$ac_[]_AC_LANG_ABBREV[]_werror_flag +ac_[]_AC_LANG_ABBREV[]_werror_flag="$ac_[]_AC_LANG_ABBREV[]_decl_warn_flag$ac_[]_AC_LANG_ABBREV[]_werror_flag" +AC_COMPILE_IFELSE([AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT([$4])], +[#ifndef $1 + (void) $1; +#endif +])], + [AS_VAR_SET([ac_Symbol], [yes])], + [AS_VAR_SET([ac_Symbol], [no])]) +ac_[]_AC_LANG_ABBREV[]_werror_flag=$ac_save_werror_flag]) +AS_VAR_IF([ac_Symbol], [yes], [$2], [$3])[]dnl +AS_VAR_POPDEF([ac_Symbol])dnl +])# AC_CHECK_DECL |