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[Qemu-devel] [PULL 31/38] configure: Add workaround for ccache and clang
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PULL 31/38] configure: Add workaround for ccache and clang |
Date: |
Fri, 22 May 2015 10:02:03 +0100 |
From: John Snow <address@hidden>
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 <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
Message-id: address@hidden
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
configure | 34 +++++++++++++++++++++++++++++++++-
1 file changed, 33 insertions(+), 1 deletion(-)
diff --git a/configure b/configure
index 24d7ecc..f758f32 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() {
@@ -4209,6 +4210,33 @@ 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 $ld runs
@@ -5502,6 +5530,10 @@ if test "$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"
--
2.1.0
- [Qemu-devel] [PULL 21/38] iotests, parallels: check for incorrectly closed image in tests, (continued)
- [Qemu-devel] [PULL 21/38] iotests, parallels: check for incorrectly closed image in tests, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 24/38] block/parallels: delay writing to BAT till bdrv_co_flush_to_os, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 22/38] block/parallels: improve image reading performance, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 23/38] block/parallels: create bat_entry_off helper, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 26/38] block/parallels: optimize linear image expansion, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 28/38] configure: handle clang -nopie argument warning, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 27/38] block/parallels: improve image writing performance further, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 29/38] configure: factor out supported flag check, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 25/38] block/parallels: add prealloc-mode and prealloc-size open paramemets, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 30/38] configure: silence glib unknown attribute __alloc_size__, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 31/38] configure: Add workaround for ccache and clang,
Stefan Hajnoczi <=
- [Qemu-devel] [PULL 33/38] block: minimal bounce buffer alignment, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 34/38] block: align bounce buffers to page, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 35/38] Revert "block: Fix unaligned zero write", Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 32/38] block: return EPERM on writes or discards to read-only devices, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 38/38] block: get_block_status: use "else" when testing the opposite condition, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 37/38] qemu-iotests: Test unaligned sub-block zero write, Stefan Hajnoczi, 2015/05/22
- [Qemu-devel] [PULL 36/38] block: Fix NULL deference for unaligned write if qiov is NULL, Stefan Hajnoczi, 2015/05/22
- Re: [Qemu-devel] [PULL 00/38] Block patches, Peter Maydell, 2015/05/22