[libcxx] Allow sanitizing libcxx with ASan+UBSan simultaneously

[kubamracek]

Summary

Allow building with LLVM_USE_SANITIZER=“Address;Undefined” (and “Undefined;Address”).

[filcab]

test/libcxx/test/config.py

628

Why don't you sanitize those?

IIRC, vptr needs stuff from libc++abi, not libc++. Is there a problem with this sanitizer on libcxx tests?
function is not available on OS X, so no need to include it. (SanitizerMask Darwin::getSupportedSanitizers() const in Driver/ToolChains.cpp)
Why remove float-divide-by-zero?

Please add a comment explaining these (also, remove any -fno-sanitize=... that you can :-) )

[kubamracek]

test/libcxx/test/config.py

628

It’s the same flags that are used for UBSan-only builds, see a few lines below. I don’t know why exactly we’re using that and it’s not the point of this patch to change them.

We can take a look at which flags should be enabled/disabled and document that, but that should happen in a separate revision.

[kubamracek]

Factoring out the UBSan flags so they’re not duplicated.

Shouldn't this be '-fsanitize="undefined;address"'?

We’re appending to the flags (with +=), so this should work as well (having -fsanitize=address -fsanitize=undefined).

[filcab]

LGTM too. We should check if those -fno-sanitize flags are actually needed, later.

lib/CMakeLists.txt

49

Please add these to line 40, above (easy to miss on Duncan's message).

[kubamracek]

Duncan sent some more comments in mail:

It'd be nice to factor this out more somehow. Can't UBSan be combined with all the others?

Yes, UBSan can be used at least with TSan and MSan, not sure about the other sanitizers and -fsanitize options. However, LLVM currently only allows some very specific options in LLVM_USE_SANITIZER (see llvm/cmake/modules/HandleLLVMOptions.cmake), and currently it only allows ASan+UBSan together. Let’s leave generalizing this for later, when someone’s actually interested in running a different sanitizer combination.

lib/CMakeLists.txt

 
 if (APPLE AND LLVM_USE_SANITIZER)
   if ("${LLVM_USE_SANITIZER}" STREQUAL "Address")
     set(LIBFILE "libclang_rt.asan_osx_dynamic.dylib")
   elseif("${LLVM_USE_SANITIZER}" STREQUAL "Undefined")
     set(LIBFILE "libclang_rt.ubsan_osx_dynamic.dylib")
   elseif("${LLVM_USE_SANITIZER}" STREQUAL "Thread")
     set(LIBFILE "libclang_rt.tsan_osx_dynamic.dylib")
+  elseif(("${LLVM_USE_SANITIZER}" STREQUAL "Address;Undefined") OR
+         ("${LLVM_USE_SANITIZER}" STREQUAL "Undefined;Address"))
+    set(LIBFILE "libclang_rt.asan_osx_dynamic.dylib")
   else()
     message(WARNING "LLVM_USE_SANITIZER=${LLVM_USE_SANITIZER} is not supported on OS X")
   endif()
   if (LIBFILE)
     execute_process(COMMAND ${CMAKE_CXX_COMPILER} -print-file-name=lib OUTPUT_VARIABLE LIBDIR RESULT_VARIABLE Result)
     if (NOT ${Result} EQUAL "0")
       message(FATAL "Failed to find library resource directory")
     endif()

test/libcxx/test/config.py

def configure_sanitizer(self):
             if cxx_path is not None:
                 symbolizer_search_paths = (
                     os.path.dirname(cxx_path) +
                     os.pathsep + symbolizer_search_paths)
             llvm_symbolizer = lit.util.which('llvm-symbolizer',
                                              symbolizer_search_paths)
             # Setup the sanitizer compile flags
             self.cxx.flags += ['-g', '-fno-omit-frame-pointer']
-            if san == 'Address':
+            if san == 'Address' or san == 'Address;Undefined' or san == 'Undefined;Address':
                 self.cxx.flags += ['-fsanitize=address']
                 if llvm_symbolizer is not None:
                     self.env['ASAN_SYMBOLIZER_PATH'] = llvm_symbolizer
                 # FIXME: Turn ODR violation back on after PR28391 is resolved
                 # https://llvm.org/bugs/show_bug.cgi?id=28391
                 self.env['ASAN_OPTIONS'] = 'detect_odr_violation=0'
                 self.config.available_features.add('asan')
                 self.config.available_features.add('sanitizer-new-delete')
                 self.cxx.compile_flags += ['-O1']
+
+                if san == 'Address;Undefined' or san == 'Undefined;Address':
+                    self.cxx.flags += ['-fsanitize=undefined',
+                                       '-fno-sanitize=vptr,function,float-divide-by-zero',
+                                       '-fno-sanitize-recover=all']
+                    self.env['UBSAN_OPTIONS'] = 'print_stacktrace=1'
+                    self.config.available_features.add('ubsan')
             elif san == 'Memory' or san == 'MemoryWithOrigins':
                 self.cxx.flags += ['-fsanitize=memory']
                 if san == 'MemoryWithOrigins':
                     self.cxx.compile_flags += [
                         '-fsanitize-memory-track-origins']
                 if llvm_symbolizer is not None:
                     self.env['MSAN_SYMBOLIZER_PATH'] = llvm_symbolizer
                 self.config.available_features.add('msan')