Adds fuzz testing for demangle

CMakeLists.txt

@@ -47,6 +47,9 @@ option (WITH_UNWIND "Enable libunwind support" ON)
 
 cmake_dependent_option (WITH_GMOCK "Use Google Mock" ON WITH_GTEST OFF)
 
+set (WITH_FUZZING none CACHE STRING "Fuzzing engine")
+set_property (CACHE WITH_FUZZING PROPERTY STRINGS none libfuzzer ossfuzz)
+
 if (NOT WITH_UNWIND)
   set (CMAKE_DISABLE_FIND_PACKAGE_Unwind ON)
 endif (NOT WITH_UNWIND)
@@ -748,6 +751,22 @@ endif (WITH_PKGCONFIG)
 
 # Unit testing
 
+if (NOT WITH_FUZZING STREQUAL "none")
+  add_executable (fuzz_demangle
+    src/fuzz_demangle.cc
+  )
+
+  if (WITH_FUZZING STREQUAL "ossfuzz")
+    set (LIB_FUZZING_ENGINE $ENV{LIB_FUZZING_ENGINE})
+    target_link_libraries (fuzz_demangle PRIVATE glog ${LIB_FUZZING_ENGINE})
+  elseif (WITH_FUZZING STREQUAL "libfuzzer")
+    target_compile_options (fuzz_demangle PRIVATE -fsanitize=fuzzer)
+    target_link_libraries (fuzz_demangle PRIVATE glog)
+  else (WITH_FUZZING STREQUAL "libfuzzer")
+    message (FATAL_ERROR "Unsupported fuzzing engine ${WITH_FUZZING}")
+  endif (WITH_FUZZING STREQUAL "ossfuzz")
+endif (NOT WITH_FUZZING STREQUAL "none")
+
 if (BUILD_TESTING)
   add_library (glogtest STATIC
     $<TARGET_OBJECTS:glog_internal>

src/fuzz_demangle.cc

@@ -0,0 +1,32 @@
+// Copyright 2023 Google LLC
+//
+// 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
+//
+//     http://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 <cstring>
+
+#include "demangle.h"
+
+extern "C" int LLVMFuzzerTestOneInput(const unsigned char *Data,
+                                      unsigned Size) {
+  if (Size >= 4095) {
+    return 0;
+  }
+  char Buffer[Size + 1];
+  std::memcpy(Buffer, Data, Size);
+  Buffer[Size] = 0;
+  char demangled[4096];
+  google::Demangle(Buffer, demangled, Size);
+  return 0;
+}