Suppress clang ubsan shift warnings rather than filtering them out

Now I've moved to a system with clang 3.8, we can suppress
clang ubsan's warnings about shift behaviour using a compiler option
rather than having to filter them out in the greplogs script.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 6 insertions, 8 deletions

diff --git a/greplogs b/greplogs
index fc13076..23690f0 100755
--- a/greplogs
+++ b/greplogs
@@ -40,17 +40,12 @@ while read f; do
     # (1) linker complaints about using getpwuid_r etc in statically linked
     # applications (which happen because of a glib awkwardness where it puts
     # those functions in the same .o as functions we use)
-    # (2) clang sanitizer runtime errors about left shifts
-    # [TODO these can probably be better suppressed with a ubsan flag
-    # now we're using a newer clang build]
-    # (3) a complaint about null_auth being an overridden common between
+    # (2) a complaint about null_auth being an overridden common between
     # libnfs and libc when statically linking
-    # (4) OSX's ancient texinfo doesn't know about UTF-8
+    # (3) OSX's ancient texinfo doesn't know about UTF-8
     egrep -i '(error:|warning:|OK DONE|assert)' < "$f" | \
       grep -v 'warning: unrecognized encoding name `UTF-8' | \
       grep -v 'statically linked applications' | \
-      grep -v 'runtime error:.*left shift.*cannot be represented' | \
-      grep -v 'runtime error:.*left shift of negative value' | \
       grep -v 'rpc_common.o.*definition of.*null_auth.*overriding common' | \
       grep -v 'libnfs.a(libnfs_la-libnfs-zdr.o): warning: common is here'
 done
diff --git a/remake-merge-builds b/remake-merge-builds
index a30c7fd..da9b101 100755
--- a/remake-merge-builds
+++ b/remake-merge-builds
@@ -24,7 +24,10 @@ do_conf() {
 do_conf all-linux-static '--cc=ccache gcc' '--enable-debug' '--static' '--disable-system'
 do_conf all '--cc=ccache gcc'
 do_conf alldbg '--cc=ccache gcc' '--enable-debug'
-do_conf clang '--cc=clang' '--cxx=clang++' '--enable-gtk' '--extra-cflags=-fsanitize=undefined -Werror'
+# We have to disable shift-base sanitizer warnings because older
+# versions of clang don't realize that -fwrapv means shifts into the sign bit, etc are
+# defined behaviour. https://bugs.llvm.org/show_bug.cgi?id=25552
+do_conf clang '--cc=clang' '--cxx=clang++' '--enable-gtk' '--extra-cflags=-fsanitize=undefined  -fno-sanitize=shift-base -Werror'
 
 # -Wno-unused-local-typedefs is working around a problem with the glib version this
 # toolchain is using where newer gcc gave a warning about its assert macro. Fixed