From patchwork Wed Mar 25 22:57:39 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Snow X-Patchwork-Id: 454814 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 7AE8A1400D5 for ; Thu, 26 Mar 2015 09:58:32 +1100 (AEDT) Received: from localhost ([::1]:41696 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YauFq-0003wW-E3 for incoming@patchwork.ozlabs.org; Wed, 25 Mar 2015 18:58:30 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47178) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YauFF-0002tj-UO for qemu-devel@nongnu.org; Wed, 25 Mar 2015 18:57:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YauF9-00083o-11 for qemu-devel@nongnu.org; Wed, 25 Mar 2015 18:57:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57537) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YauF8-00083g-OX for qemu-devel@nongnu.org; Wed, 25 Mar 2015 18:57:46 -0400 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t2PMvjZZ019452 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 25 Mar 2015 18:57:45 -0400 Received: from scv.usersys.redhat.com (dhcp-17-29.bos.redhat.com [10.18.17.29]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t2PMvfUI017716; Wed, 25 Mar 2015 18:57:44 -0400 From: John Snow To: qemu-devel@nongnu.org Date: Wed, 25 Mar 2015 18:57:39 -0400 Message-Id: <1427324259-1481-5-git-send-email-jsnow@redhat.com> In-Reply-To: <1427324259-1481-1-git-send-email-jsnow@redhat.com> References: <1427324259-1481-1-git-send-email-jsnow@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: peter.maydell@linaro.org, John Snow , stefanha@redhat.com Subject: [Qemu-devel] [PATCH v5 4/4] configure: Add workaround for ccache and clang X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Test if ccache is interfering with semantic analysis of macros, disable its habit of trying to compile already pre-processed versions of code if so. ccache attempts to save time by compiling pre-processed versions of code, but this disturbs clang's static analysis enough to produce false positives. ccache allows us to disable this feature, opting instead to compile the original version instead of its preprocessed version. This makes ccache much slower for cache misses, but at least it becomes usable with QEMU/clang. This workaround only activates for users using ccache AND clang, and only if their configuration is observed to be producing warnings. You may need to clear your ccache for builds started without -Werror, as those may continue to produce warnings from the cache. Thanks to Peter Eisentraut for his writeup on the issue: http://peter.eisentraut.org/blog/2014/12/01/ccache-and-clang-part-3/ Signed-off-by: John Snow --- configure | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) diff --git a/configure b/configure index c02a26b..dfd23ad 100755 --- a/configure +++ b/configure @@ -103,7 +103,8 @@ update_cxxflags() { } compile_object() { - do_cc $QEMU_CFLAGS -c -o $TMPO $TMPC + local_cflags="$1" + do_cc $QEMU_CFLAGS $local_cflags -c -o $TMPO $TMPC } compile_prog() { @@ -4169,6 +4170,33 @@ if compile_prog "" "" ; then getauxval=yes fi +######################################## +# check if ccache is interfering with +# semantic analysis of macros + +ccache_cpp2=no +cat > $TMPC << EOF +static const int Z = 1; +#define fn() ({ Z; }) +#define TAUT(X) ((X) == Z) +#define PAREN(X, Y) (X == Y) +#define ID(X) (X) +int main(int argc, char *argv[]) +{ + int x = 0, y = 0; + x = ID(x); + x = fn(); + fn(); + if (PAREN(x, y)) return 0; + if (TAUT(Z)) return 0; + return 0; +} +EOF + +if ! compile_object "-Werror"; then + ccache_cpp2=yes +fi + ########################################## # End of CC checks # After here, no more $cc or $ld runs @@ -5461,6 +5489,10 @@ if test "$numa" = "yes"; then echo "CONFIG_NUMA=y" >> $config_host_mak fi +if test "$ccache_cpp2" = "yes"; then + echo "export CCACHE_CPP2=y" >> $config_host_mak +fi + # build tree in object directory in case the source is not in the current directory DIRS="tests tests/tcg tests/tcg/cris tests/tcg/lm32 tests/libqos tests/qapi-schema tests/tcg/xtensa tests/qemu-iotests" DIRS="$DIRS fsdev"