[Qemu-devel] [PATCH] vhost build fix for i386

[Wolfgang Mauerer]

vhost.c uses __sync_fetch_and_and(), which is only
available for -march=i486 and above (see
https://bugzilla.redhat.com/show_bug.cgi?id=624279).

Signed-off-by: Wolfgang Mauerer <address@hidden>
---
 configure |   23 +++++++++++++++++++++++
 1 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/configure b/configure
index 88159ac..3b6facb 100755
--- a/configure
+++ b/configure
@@ -2464,6 +2464,29 @@ if test "$trace_backend" = "dtrace"; then
 fi
 
 ##########################################
+# __sync_fetch_and_and requires at least -march=i486. Many toolchains
+# use i686 as default anyway, but for those that don't, an explicit
+# specification is necessary
+if test $vhost_net = "yes" && test $cpu = "i386"; then
+  cat > $TMPC << EOF
+int sfaa(unsigned *ptr)
+{
+  return __sync_fetch_and_and(ptr, 0);
+}
+
+int main(int argc, char **argv)
+{
+  int val = 42;
+  sfaa(&val);
+  return val;
+}
+EOF
+  if ! compile_prog "" "" ; then
+    CFLAGS+="-march=i486"
+  fi
+fi
+
+##########################################
 # End of CC checks
 # After here, no more $cc or $ld runs
 
-- 
1.6.4