From c0f075bdee5edabf8f19b68e0880fbd249a89653 Mon Sep 17 00:00:00 2001
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From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
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Date: Sat, 3 Jan 2015 15:09:59 +0100
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Subject: [PATCH] Add test for -Wunused-but-set-variable
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The -Wunused-but-set-variable option does not exist in some old gcc
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versions (gcc 4.5.x), so using it unconditionally breaks the build
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with such compilers.
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This commit introduces the AX_CHECK_COMPILE_FLAG m4 macro taken from
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the autoconf-archive
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(http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_check_compile_flag.m4),
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and uses it to detect if the -Wunused-but-set-variable option is
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supported, and only uses it in this case.
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Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
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(rebased against v0.1.0)
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Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
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(rebased against v0.6.3)
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Signed-off-by: Adam Duskett <Aduskett@gmail.com>
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---
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Makefile.am | 1 +
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configure.ac | 6 ++-
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m4/ax_check_compile_flag.m4 | 74 +++++++++++++++++++++++++++++++++++++
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3 files changed, 79 insertions(+), 2 deletions(-)
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create mode 100644 m4/ax_check_compile_flag.m4
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diff --git a/Makefile.am b/Makefile.am
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index f961fdb..3ddbe59 100644
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--- a/Makefile.am
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+++ b/Makefile.am
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@@ -151,6 +151,7 @@ janus_CFLAGS = \
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-DEVENTDIR=\"$(eventdir)\" \
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-DLOGGERDIR=\"$(loggerdir)\" \
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-DCONFDIR=\"$(confdir)\" \
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+ @GCC_WARN_UNUSED_BUT_SET@ \
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$(BORINGSSL_CFLAGS) \
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$(NULL)
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diff --git a/configure.ac b/configure.ac
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index ca17a29..beef91a 100644
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--- a/configure.ac
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+++ b/configure.ac
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@@ -13,6 +13,9 @@ AM_SILENT_RULES([yes])
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AC_USE_SYSTEM_EXTENSIONS
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AC_PROG_CC
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+AX_CHECK_COMPILE_FLAG([-Wunused-but-set-variable],
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+ [GCC_WARN_UNUSED_BUT_SET=-Wunused-but-set-variable])
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+AC_SUBST(GCC_WARN_UNUSED_BUT_SET)
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LT_PREREQ([2.2])
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LT_INIT
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@@ -64,8 +67,7 @@ clang*)
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CFLAGS="$CFLAGS \
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-Wcast-align \
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-Wno-override-init \
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- -Wunsafe-loop-optimizations \
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- -Wunused-but-set-variable"
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+ -Wunsafe-loop-optimizations"
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esac
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JANUS_VERSION=103
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diff --git a/m4/ax_check_compile_flag.m4 b/m4/ax_check_compile_flag.m4
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new file mode 100644
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index 0000000..51df0c0
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--- /dev/null
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+++ b/m4/ax_check_compile_flag.m4
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@@ -0,0 +1,74 @@
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+# ===========================================================================
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+# http://www.gnu.org/software/autoconf-archive/ax_check_compile_flag.html
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+# ===========================================================================
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+#
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+# SYNOPSIS
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+#
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+# AX_CHECK_COMPILE_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS], [INPUT])
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+#
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+# DESCRIPTION
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+#
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+# Check whether the given FLAG works with the current language's compiler
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+# or gives an error. (Warnings, however, are ignored)
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+#
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+# ACTION-SUCCESS/ACTION-FAILURE are shell commands to execute on
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+# success/failure.
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+#
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+# If EXTRA-FLAGS is defined, it is added to the current language's default
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+# flags (e.g. CFLAGS) when the check is done. The check is thus made with
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+# the flags: "CFLAGS EXTRA-FLAGS FLAG". This can for example be used to
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+# force the compiler to issue an error when a bad flag is given.
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+#
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+# INPUT gives an alternative input source to AC_COMPILE_IFELSE.
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+#
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+# NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this
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+# macro in sync with AX_CHECK_{PREPROC,LINK}_FLAG.
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+#
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+# LICENSE
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+#
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+# Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
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+# Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com>
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+#
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+# This program is free software: you can redistribute it and/or modify it
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+# under the terms of the GNU General Public License as published by the
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+# Free Software Foundation, either version 3 of the License, or (at your
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+# option) any later version.
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+#
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+# This program is distributed in the hope that it will be useful, but
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+# WITHOUT ANY WARRANTY; without even the implied warranty of
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+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
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+# Public License for more details.
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+#
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+# You should have received a copy of the GNU General Public License along
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+# with this program. If not, see <http://www.gnu.org/licenses/>.
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+#
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+# As a special exception, the respective Autoconf Macro's copyright owner
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+# gives unlimited permission to copy, distribute and modify the configure
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+# scripts that are the output of Autoconf when processing the Macro. You
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+# need not follow the terms of the GNU General Public License when using
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+# or distributing such scripts, even though portions of the text of the
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+# Macro appear in them. The GNU General Public License (GPL) does govern
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+# all other use of the material that constitutes the Autoconf Macro.
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+#
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+# This special exception to the GPL applies to versions of the Autoconf
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+# Macro released by the Autoconf Archive. When you make and distribute a
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+# modified version of the Autoconf Macro, you may extend this special
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+# exception to the GPL to apply to your modified version as well.
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+
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+#serial 3
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+
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+AC_DEFUN([AX_CHECK_COMPILE_FLAG],
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+[AC_PREREQ(2.59)dnl for _AC_LANG_PREFIX
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+AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_[]_AC_LANG_ABBREV[]flags_$4_$1])dnl
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+AC_CACHE_CHECK([whether _AC_LANG compiler accepts $1], CACHEVAR, [
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+ ax_check_save_flags=$[]_AC_LANG_PREFIX[]FLAGS
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+ _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $4 $1"
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+ AC_COMPILE_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])],
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+ [AS_VAR_SET(CACHEVAR,[yes])],
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+ [AS_VAR_SET(CACHEVAR,[no])])
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+ _AC_LANG_PREFIX[]FLAGS=$ax_check_save_flags])
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+AS_IF([test x"AS_VAR_GET(CACHEVAR)" = xyes],
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+ [m4_default([$2], :)],
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+ [m4_default([$3], :)])
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+AS_VAR_POPDEF([CACHEVAR])dnl
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+])dnl AX_CHECK_COMPILE_FLAGS
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--
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2.20.1
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