Rewrite libfuzzer buildfile for GN.

third_party/libFuzzer/BUILD.gn

@@ -1,41 +1,28 @@
-# Copyright 2016 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
+# Copyright 2022 The GPGMM 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
+#
+# 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.
 
 import("///build/config/sanitizers/sanitizers.gni")
 
-config("warnings") {
+config("libfuzzer_flags") {
   if (is_clang) {
     cflags = [
       "-Wno-shadow",
-
-      # See crbug.com/932188, libFuzzer does not check the result of write()
-      # when it does raw printing.
       "-Wno-unused-result",
     ]
   }
 }
 
-# Engine should be compiled without coverage (infinite loop in trace_cmp).
-fuzzing_engine_remove_configs = [
-  "//build/config/coverage:default_coverage",
-  "//build/config/sanitizers:default_sanitizer_flags",
-]
-
-# Add any sanitizer flags back. In MSAN builds, instrumenting libfuzzer with
-# MSAN is necessary since all parts of the binary need to be instrumented for it
-# to work. ASAN builds are more subtle: libfuzzer depends on features from the
-# C++ STL. If it were not instrumented, templates would be insantiated without
-# ASAN from libfuzzer and with ASAN in other TUs. The linker might merge
-# instrumented template instantiations with non-instrumented ones (which could
-# have a different ABI) in the final binary, which is problematic for TUs
-# expecting one particular ABI (https://crbug.com/915422). The other sanitizers
-# are added back for the same reason.
-fuzzing_engine_add_configs = [
-  "//build/config/sanitizers:default_sanitizer_flags_but_coverage",
-  ":warnings",
-]
-
 source_set("libfuzzer") {
   sources = [
     "src/FuzzerCrossOver.cpp",
@@ -50,6 +37,7 @@ source_set("libfuzzer") {
     "src/FuzzerIOPosix.cpp",
     "src/FuzzerIOWindows.cpp",
     "src/FuzzerLoop.cpp",
+    "src/FuzzerMain.cpp",
     "src/FuzzerMerge.cpp",
     "src/FuzzerMutate.cpp",
     "src/FuzzerSHA1.cpp",
@@ -62,24 +50,13 @@ source_set("libfuzzer") {
     "src/FuzzerUtilWindows.cpp",
   ]
 
-  if (!is_ios) {
-    sources += [ "src/FuzzerMain.cpp" ]
-  }
-
-  configs -= fuzzing_engine_remove_configs
-  configs += fuzzing_engine_add_configs
-
-  deps = []
-  if (is_fuchsia) {
-    deps += [ "//third_party/fuchsia-sdk/sdk:fdio" ]
-  }
-}
-
-if (use_afl) {
-  source_set("afl_driver") {
-    sources = [ "src/afl/afl_driver.cpp" ]
+  configs -= [
+    "//build/config/coverage:default_coverage",
+    "//build/config/sanitizers:default_sanitizer_flags",
+  ]
 
-    configs -= fuzzing_engine_remove_configs
-    configs += fuzzing_engine_add_configs
-  }
+  configs += [
+    "//build/config/sanitizers:default_sanitizer_flags_but_coverage",
+    ":libfuzzer_flags",
+  ]
 }