From c0f075bdee5edabf8f19b68e0880fbd249a89653 Mon Sep 17 00:00:00 2001 From: Thomas Petazzoni Date: Sat, 3 Jan 2015 15:09:59 +0100 Subject: [PATCH] Add test for -Wunused-but-set-variable The -Wunused-but-set-variable option does not exist in some old gcc versions (gcc 4.5.x), so using it unconditionally breaks the build with such compilers. This commit introduces the AX_CHECK_COMPILE_FLAG m4 macro taken from the autoconf-archive (http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_check_compile_flag.m4), and uses it to detect if the -Wunused-but-set-variable option is supported, and only uses it in this case. Signed-off-by: Thomas Petazzoni --- Makefile.am | 2 +- configure.ac | 3 ++ m4/ax_check_compile_flag.m4 | 74 +++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 78 insertions(+), 1 deletion(-) create mode 100644 m4/ax_check_compile_flag.m4 diff --git a/Makefile.am b/Makefile.am index 5d23e0b..0f51f6a 100644 --- a/Makefile.am +++ b/Makefile.am @@ -6,7 +6,7 @@ AM_CFLAGS = \ -Wnested-externs -Wstrict-prototypes -Wunsafe-loop-optimizations \ -Wwrite-strings -Wno-missing-field-initializers -Wno-unused-parameter \ -Wcast-align -Wformat-nonliteral -Wformat-security -Wswitch-default \ - -Wmissing-include-dirs -Waggregate-return -Wunused-but-set-variable \ + -Wmissing-include-dirs -Waggregate-return @GCC_WARN_UNUSED_BUT_SET@ \ -Warray-bounds -Wold-style-definition -Wsign-compare -Wlarger-than=65537 AM_CFLAGS += -Wno-undef # sophiasip is not -Wundef--safe AM_CFLAGS += -Wredundant-decls # sophiasip also contains redundant declarations diff --git a/configure.ac b/configure.ac index 17870a7..f9bb1e4 100644 --- a/configure.ac +++ b/configure.ac @@ -7,6 +7,9 @@ AM_SILENT_RULES([yes]) AC_GNU_SOURCE AC_PROG_CC +AX_CHECK_COMPILE_FLAG([-Wunused-but-set-variable], + [GCC_WARN_UNUSED_BUT_SET=-Wunused-but-set-variable]) +AC_SUBST(GCC_WARN_UNUSED_BUT_SET) LT_PREREQ([2.2]) LT_INIT diff --git a/m4/ax_check_compile_flag.m4 b/m4/ax_check_compile_flag.m4 new file mode 100644 index 0000000..51df0c0 --- /dev/null +++ b/m4/ax_check_compile_flag.m4 @@ -0,0 +1,74 @@ +# =========================================================================== +# http://www.gnu.org/software/autoconf-archive/ax_check_compile_flag.html +# =========================================================================== +# +# SYNOPSIS +# +# AX_CHECK_COMPILE_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS], [INPUT]) +# +# DESCRIPTION +# +# Check whether the given FLAG works with the current language's compiler +# or gives an error. (Warnings, however, are ignored) +# +# ACTION-SUCCESS/ACTION-FAILURE are shell commands to execute on +# success/failure. +# +# If EXTRA-FLAGS is defined, it is added to the current language's default +# flags (e.g. CFLAGS) when the check is done. The check is thus made with +# the flags: "CFLAGS EXTRA-FLAGS FLAG". This can for example be used to +# force the compiler to issue an error when a bad flag is given. +# +# INPUT gives an alternative input source to AC_COMPILE_IFELSE. +# +# NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this +# macro in sync with AX_CHECK_{PREPROC,LINK}_FLAG. +# +# LICENSE +# +# Copyright (c) 2008 Guido U. Draheim +# Copyright (c) 2011 Maarten Bosmans +# +# 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. +# +# You should have received a copy of the GNU General Public License along +# with this program. If not, see . +# +# As a special exception, the respective Autoconf Macro's copyright owner +# gives unlimited permission to copy, distribute and modify the configure +# scripts that are the output of Autoconf when processing the Macro. You +# need not follow the terms of the GNU General Public License when using +# or distributing such scripts, even though portions of the text of the +# Macro appear in them. The GNU General Public License (GPL) does govern +# all other use of the material that constitutes the Autoconf Macro. +# +# This special exception to the GPL applies to versions of the Autoconf +# Macro released by the Autoconf Archive. When you make and distribute a +# modified version of the Autoconf Macro, you may extend this special +# exception to the GPL to apply to your modified version as well. + +#serial 3 + +AC_DEFUN([AX_CHECK_COMPILE_FLAG], +[AC_PREREQ(2.59)dnl for _AC_LANG_PREFIX +AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_[]_AC_LANG_ABBREV[]flags_$4_$1])dnl +AC_CACHE_CHECK([whether _AC_LANG compiler accepts $1], CACHEVAR, [ + ax_check_save_flags=$[]_AC_LANG_PREFIX[]FLAGS + _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $4 $1" + AC_COMPILE_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])], + [AS_VAR_SET(CACHEVAR,[yes])], + [AS_VAR_SET(CACHEVAR,[no])]) + _AC_LANG_PREFIX[]FLAGS=$ax_check_save_flags]) +AS_IF([test x"AS_VAR_GET(CACHEVAR)" = xyes], + [m4_default([$2], :)], + [m4_default([$3], :)]) +AS_VAR_POPDEF([CACHEVAR])dnl +])dnl AX_CHECK_COMPILE_FLAGS -- 2.1.0