1From c0f075bdee5edabf8f19b68e0880fbd249a89653 Mon Sep 17 00:00:00 2001 2From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> 3Date: Sat, 3 Jan 2015 15:09:59 +0100 4Subject: [PATCH] Add test for -Wunused-but-set-variable 5 6The -Wunused-but-set-variable option does not exist in some old gcc 7versions (gcc 4.5.x), so using it unconditionally breaks the build 8with such compilers. 9 10This commit introduces the AX_CHECK_COMPILE_FLAG m4 macro taken from 11the autoconf-archive 12(http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_check_compile_flag.m4), 13and uses it to detect if the -Wunused-but-set-variable option is 14supported, and only uses it in this case. 15 16Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> 17(rebased against v0.1.0) 18Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de> 19(rebased against v0.6.3) 20Signed-off-by: Adam Duskett <Aduskett@gmail.com> 21--- 22 Makefile.am | 1 + 23 configure.ac | 6 ++- 24 m4/ax_check_compile_flag.m4 | 74 +++++++++++++++++++++++++++++++++++++ 25 3 files changed, 79 insertions(+), 2 deletions(-) 26 create mode 100644 m4/ax_check_compile_flag.m4 27 28diff --git a/Makefile.am b/Makefile.am 29index f961fdb..3ddbe59 100644 30--- a/Makefile.am 31+++ b/Makefile.am 32@@ -151,6 +151,7 @@ janus_CFLAGS = \ 33 -DEVENTDIR=\"$(eventdir)\" \ 34 -DLOGGERDIR=\"$(loggerdir)\" \ 35 -DCONFDIR=\"$(confdir)\" \ 36+ @GCC_WARN_UNUSED_BUT_SET@ \ 37 $(BORINGSSL_CFLAGS) \ 38 $(NULL) 39 40diff --git a/configure.ac b/configure.ac 41index ca17a29..beef91a 100644 42--- a/configure.ac 43+++ b/configure.ac 44@@ -13,6 +13,9 @@ AM_SILENT_RULES([yes]) 45 AC_USE_SYSTEM_EXTENSIONS 46 47 AC_PROG_CC 48+AX_CHECK_COMPILE_FLAG([-Wunused-but-set-variable], 49+ [GCC_WARN_UNUSED_BUT_SET=-Wunused-but-set-variable]) 50+AC_SUBST(GCC_WARN_UNUSED_BUT_SET) 51 52 LT_PREREQ([2.2]) 53 LT_INIT 54@@ -64,8 +67,7 @@ clang*) 55 CFLAGS="$CFLAGS \ 56 -Wcast-align \ 57 -Wno-override-init \ 58- -Wunsafe-loop-optimizations \ 59- -Wunused-but-set-variable" 60+ -Wunsafe-loop-optimizations" 61 esac 62 63 JANUS_VERSION=103 64diff --git a/m4/ax_check_compile_flag.m4 b/m4/ax_check_compile_flag.m4 65new file mode 100644 66index 0000000..51df0c0 67--- /dev/null 68+++ b/m4/ax_check_compile_flag.m4 69@@ -0,0 +1,74 @@ 70+# =========================================================================== 71+# http://www.gnu.org/software/autoconf-archive/ax_check_compile_flag.html 72+# =========================================================================== 73+# 74+# SYNOPSIS 75+# 76+# AX_CHECK_COMPILE_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS], [INPUT]) 77+# 78+# DESCRIPTION 79+# 80+# Check whether the given FLAG works with the current language's compiler 81+# or gives an error. (Warnings, however, are ignored) 82+# 83+# ACTION-SUCCESS/ACTION-FAILURE are shell commands to execute on 84+# success/failure. 85+# 86+# If EXTRA-FLAGS is defined, it is added to the current language's default 87+# flags (e.g. CFLAGS) when the check is done. The check is thus made with 88+# the flags: "CFLAGS EXTRA-FLAGS FLAG". This can for example be used to 89+# force the compiler to issue an error when a bad flag is given. 90+# 91+# INPUT gives an alternative input source to AC_COMPILE_IFELSE. 92+# 93+# NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this 94+# macro in sync with AX_CHECK_{PREPROC,LINK}_FLAG. 95+# 96+# LICENSE 97+# 98+# Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de> 99+# Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com> 100+# 101+# This program is free software: you can redistribute it and/or modify it 102+# under the terms of the GNU General Public License as published by the 103+# Free Software Foundation, either version 3 of the License, or (at your 104+# option) any later version. 105+# 106+# This program is distributed in the hope that it will be useful, but 107+# WITHOUT ANY WARRANTY; without even the implied warranty of 108+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General 109+# Public License for more details. 110+# 111+# You should have received a copy of the GNU General Public License along 112+# with this program. If not, see <http://www.gnu.org/licenses/>. 113+# 114+# As a special exception, the respective Autoconf Macro's copyright owner 115+# gives unlimited permission to copy, distribute and modify the configure 116+# scripts that are the output of Autoconf when processing the Macro. You 117+# need not follow the terms of the GNU General Public License when using 118+# or distributing such scripts, even though portions of the text of the 119+# Macro appear in them. The GNU General Public License (GPL) does govern 120+# all other use of the material that constitutes the Autoconf Macro. 121+# 122+# This special exception to the GPL applies to versions of the Autoconf 123+# Macro released by the Autoconf Archive. When you make and distribute a 124+# modified version of the Autoconf Macro, you may extend this special 125+# exception to the GPL to apply to your modified version as well. 126+ 127+#serial 3 128+ 129+AC_DEFUN([AX_CHECK_COMPILE_FLAG], 130+[AC_PREREQ(2.59)dnl for _AC_LANG_PREFIX 131+AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_[]_AC_LANG_ABBREV[]flags_$4_$1])dnl 132+AC_CACHE_CHECK([whether _AC_LANG compiler accepts $1], CACHEVAR, [ 133+ ax_check_save_flags=$[]_AC_LANG_PREFIX[]FLAGS 134+ _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $4 $1" 135+ AC_COMPILE_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])], 136+ [AS_VAR_SET(CACHEVAR,[yes])], 137+ [AS_VAR_SET(CACHEVAR,[no])]) 138+ _AC_LANG_PREFIX[]FLAGS=$ax_check_save_flags]) 139+AS_IF([test x"AS_VAR_GET(CACHEVAR)" = xyes], 140+ [m4_default([$2], :)], 141+ [m4_default([$3], :)]) 142+AS_VAR_POPDEF([CACHEVAR])dnl 143+])dnl AX_CHECK_COMPILE_FLAGS 144-- 1452.20.1 146 147