pw_fuzzer: Add asan_default_options

This CL adds a means to specify ASAN_OPTIONS in order to avoid false
positives introduced by fuzz tests which are only partially
instrumented. In fuzz tests, the engine is excluded from instrumentation
to avoid polluting the sanitizer coverage with code paths not related to
the target being fuzzed.

Change-Id: I642668026eeaa9e6c051fe64050512f3cbb32ff1
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/234452
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Reviewed-by: Taylor Cramer <cramertj@google.com>
Commit-Queue: Aaron Green <aarongreen@google.com>

pw_fuzzer/BUILD.gn

@@ -71,6 +71,10 @@ pw_test_group("tests") {
  ]
 }
 
+pw_source_set("asan_default_options") {
+ sources = [ "asan_default_options.c" ]
+}
+
 ################################################################################
 # FuzzTest support
 #
@@ -182,7 +186,10 @@ if (dir_pw_third_party_fuzztest == "") {
  if (pw_toolchain_OSS_FUZZ_ENABLED) {
  deps = [ "$dir_pw_unit_test:simple_printing_main" ]
  } else {
- deps = [ "$dir_pw_third_party/fuzztest/fuzztest:fuzztest_gtest_main" ]
+ deps = [
+ ":asan_default_options",
+ "$dir_pw_third_party/fuzztest/fuzztest:fuzztest_gtest_main",
+ ]
  }
  }
 }

pw_fuzzer/asan_default_options.c

@@ -0,0 +1,28 @@
+// Copyright 2024 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+#include <sanitizer/asan_interface.h>
+
+// Sets the default options for AddressSanitizer.
+//
+// See https://github.com/google/sanitizers/wiki/AddressSanitizerFlags for
+// more details.
+const char* __asan_default_options(void) {
+ return
+ // FuzzTest is not instrumented to avoid polluting the code coverage used
+ // to guide fuzzing. It also uses STL containers such as vectors, leading
+ // to false positives such as those described in
+ // github.com/google/sanitizers/wiki/AddressSanitizerContainerOverflow
+ "detect_container_overflow=0";
+}