[Mesa-dev] [PATCH 1/2] scons: Allow building with Address Sanitizer.

[Jose Fonseca]

On 13/04/16 14:41, Emil Velikov wrote:
> Hi Jose,
>
> On 12 April 2016 at 17:03, Jose Fonseca <jfonseca at vmware.com> wrote:
>> libasan is never linked to shared objects (which doesn't go well with
>> -z,defs).  It must either be linked to the main executable, or (more
>> practically for OpenGL drivers) be pre-loaded via LD_PRELOAD.
>>
>> Otherwise works.
>>
>> I didn't find anything with llvmpipe.  I suspect the fact that the
>> JIT compiled code isn't instrumented means there are lots of errors it
>> can't catch.
>>
>> But for non-JIT drivers, the Address/Leak Sanitizers seem like a faster
>> alternative to Valgrind.
>>
>> Usage (Ubuntu 15.10):
>>
>>     scons asan=1 libgl-xlib
>>     export LD_LIBRARY_PATH=$PWD/build/linux-x86_64-debug/gallium/targets/libgl-xlib
>>     LD_PRELOAD=libasan.so.2 any-opengl-application
>
> Just a bit of more info for anyone unfamiliar/interested. Not meant to
> stir the waters.
>
> Traditionally, the sanitizers were static libraries that one used for
> link in each binary. As of recently one can opt for the shared library
> libasan.so. Imho should opt against using the shared lib pro temp. as
> it has multiple drawbacks (experimental, unsupported, has worse
> performance ...) [1].
>
> -Emil
>
> [1] https://github.com/google/sanitizers/wiki/AddressSanitizerAsDso

I managed to link asan statically, but it doesn't work.

This is because we often need to free() things from other libraries 
(Xlib) and vice-versa, and it will crash as soon as that happens.

For the record, my patch for statically linking asan was something like:

+    if env['asan']:
+        if gcc_compat:
+            env.Append(CCFLAGS = [
+                '-fsanitize=address',
+            ])
+            env.Append(LINKFLAGS = [
+                '-fsanitize=address',
+                '-static-libasan',
+            ])
+            env['_LIBFLAGS'] = env['_LIBFLAGS'] + ' -Wl,-Bstatic -lasan 
-Wl,-Bdynamic'
+            env.Append(LIBS = ['asan'])
+

Maybe statically linking the asan is better, but only when talking about 
the main program.  But in mesa we build the drivers, not the main program.


Jose