cppgc: Fix cppgc build

The CPPGC_BUILD_IN_V8 define (used for tracing) isn't propagated from
v8_base_without_compiler to cppgc_base, which breaks build with
perfetto. Instead use a gn args to specify standalone builds (defaulted
to false) and use that to choose the right tracing implementation.

Bug: chromium:1056170
Change-Id: I70bce819d45fb133b6f932a50a5d027e39f3e5b9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2555007
Auto-Submit: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71356}

BUILD.gn

@@ -460,6 +460,10 @@ config("libbase_config") {
   }
 }
 
+# Standalone cppgc cannot be built within chrome or with perfetto.
+assert(!cppgc_is_standalone || !build_with_chromium)
+assert(!cppgc_is_standalone || !v8_use_perfetto)
+
 # This config should be applied to code using the cppgc_base.
 config("cppgc_base_config") {
   defines = []
@@ -472,6 +476,9 @@ config("cppgc_base_config") {
   if (cppgc_enable_young_generation) {
     defines += [ "CPPGC_YOUNG_GENERATION" ]
   }
+  if (!cppgc_is_standalone) {
+    defines += [ "CPPGC_BUILD_IN_V8" ]
+  }
 }
 
 # This config should be applied to code using the libsampler.
@@ -3825,8 +3832,6 @@ v8_source_set("v8_base_without_compiler") {
     ":cppgc_base_config",
   ]
 
-  defines = [ "CPPGC_BUILD_IN_V8" ]
-
   deps = [
     ":cppgc_base",
     ":torque_generated_definitions",
@@ -4427,7 +4432,6 @@ v8_source_set("cppgc_base") {
   visibility = [ ":*" ]
 
   sources = [
-    "//base/trace_event/common/trace_event_common.h",
     "include/cppgc/allocation.h",
     "include/cppgc/common.h",
     "include/cppgc/custom-space.h",
@@ -4531,6 +4535,10 @@ v8_source_set("cppgc_base") {
     "src/heap/cppgc/write-barrier.cc",
   ]
 
+  if (cppgc_is_standalone) {
+    sources += [ "//base/trace_event/common/trace_event_common.h" ]
+  }
+
   if (cppgc_enable_caged_heap) {
     sources += [
       "include/cppgc/internal/caged-heap-local-data.h",
@@ -4905,9 +4913,14 @@ if (is_component_build) {
 
     configs = [ ":internal_config" ]
 
+    if (!cppgc_is_standalone) {
+      deps = [ ":v8" ]
+    }
+
     public_configs = [ ":external_config" ]
   }
 
+  if (cppgc_is_standalone) {
     v8_component("cppgc_for_testing") {
       testonly = true
 
@@ -4916,6 +4929,7 @@ if (is_component_build) {
       configs = [ ":internal_config" ]
       public_configs = [ ":external_config" ]
     }
+  }
 
   v8_component("v8_cppgc_shared_for_testing") {
     testonly = true
@@ -4952,9 +4966,14 @@ if (is_component_build) {
   group("cppgc") {
     public_deps = [ ":cppgc_base" ]
 
+    if (!cppgc_is_standalone) {
+      deps = [ ":v8" ]
+    }
+
     public_configs = [ ":external_config" ]
   }
 
+  if (cppgc_is_standalone) {
     group("cppgc_for_testing") {
       testonly = true
 
@@ -4962,6 +4981,7 @@ if (is_component_build) {
 
       public_configs = [ ":external_config" ]
     }
+  }
 
   group("v8_cppgc_shared_for_testing") {
     testonly = true
@@ -5082,8 +5102,9 @@ if (want_v8_shell) {
   }
 }
 
-v8_executable("cppgc_for_v8_embedders") {
-  sources = [ "samples/cppgc/cppgc-for-v8-embedders.cc" ]
+if (cppgc_is_standalone) {
+  v8_executable("cppgc_standalone") {
+    sources = [ "samples/cppgc/cppgc-standalone.cc" ]
 
     configs = [
       # Note: don't use :internal_config here because this target will get
@@ -5092,15 +5113,11 @@ v8_executable("cppgc_for_v8_embedders") {
       ":internal_config_base",
     ]
 
-  deps = [
-    ":cppgc",
-    ":v8_libplatform",
-    "//build/win:default_exe_manifest",
-  ]
-}
-
-v8_executable("cppgc_standalone") {
-  sources = [ "samples/cppgc/cppgc-standalone.cc" ]
+    deps = [ ":cppgc" ]
+  }
+} else {
+  v8_executable("cppgc_for_v8_embedders") {
+    sources = [ "samples/cppgc/cppgc-for-v8-embedders.cc" ]
 
     configs = [
       # Note: don't use :internal_config here because this target will get
@@ -5109,7 +5126,12 @@ v8_executable("cppgc_standalone") {
       ":internal_config_base",
     ]
 
-  deps = [ ":cppgc" ]
+    deps = [
+      ":v8",
+      ":v8_libplatform",
+      "//build/win:default_exe_manifest",
+    ]
+  }
 }
 
 template("v8_fuzzer") {

gni/v8.gni

@@ -71,6 +71,8 @@ declare_args() {
   v8_enable_conservative_stack_scanning = false
 
   v8_enable_google_benchmark = checkout_google_benchmark
+
+  cppgc_is_standalone = false
 }
 
 if (v8_use_external_startup_data == "") {

src/heap/cppgc/trace-event.h

@@ -7,6 +7,7 @@
 
 #if CPPGC_BUILD_IN_V8
 #include "src/tracing/trace-event.h"
+using ConvertableToTraceFormat = v8::ConvertableToTraceFormat;
 #else
 // This is a subset of stc/tracing/trace-event.h required to support
 // tracing in the cppgc standalone library using TracingController.

test/benchmarks/cpp/cppgc/BUILD.gn

@@ -28,10 +28,12 @@ if (v8_enable_google_benchmark) {
       "../../../../test/unittests/heap/cppgc/test-platform.h",
       "utils.h",
     ]
-    deps = [
-      "../../../..:cppgc_for_testing",
-      "//third_party/google_benchmark:benchmark_main",
-    ]
+    deps = [ "//third_party/google_benchmark:benchmark_main" ]
+    if (cppgc_is_standalone) {
+      deps += [ "../../../..:cppgc_for_testing" ]
+    } else {
+      deps += [ "../../../..:v8_for_testing" ]
+    }
   }
 
   v8_executable("cppgc_basic_benchmarks") {
@@ -48,8 +50,12 @@ if (v8_enable_google_benchmark) {
     ]
     deps = [
       ":cppgc_benchmark_support",
-      "../../../..:cppgc_for_testing",
       "//third_party/google_benchmark:benchmark_main",
     ]
+    if (cppgc_is_standalone) {
+      deps += [ "../../../..:cppgc_for_testing" ]
+    } else {
+      deps += [ "../../../..:v8_for_testing" ]
+    }
   }
 }

test/unittests/BUILD.gn

@@ -57,7 +57,8 @@ v8_source_set("v8_cppgc_shared_unittests_sources") {
 # Stand-alone target for C++ GC unittests. This is used to ensure that it
 # builds without V8 as well. They are also included in the regular unittests
 # target for simplicity.
-v8_executable("cppgc_unittests") {
+if (cppgc_is_standalone) {
+  v8_executable("cppgc_unittests") {
     testonly = true
 
     configs = [
@@ -74,6 +75,7 @@ v8_executable("cppgc_unittests") {
       "//testing/gmock",
       "//testing/gtest",
     ]
+  }
 }
 
 v8_source_set("cppgc_unittests_sources") {
@@ -142,7 +144,6 @@ v8_executable("unittests") {
   #}],
 
   deps = [
-    ":cppgc_unittests_sources",
     ":unittests_sources",
     ":v8_cppgc_shared_unittests_sources",
     "../..:v8_for_testing",
@@ -153,6 +154,10 @@ v8_executable("unittests") {
     "//testing/gtest",
   ]
 
+  if (!cppgc_is_standalone) {
+    deps += [ ":cppgc_unittests_sources" ]
+  }
+
   data_deps = [ "../../tools:v8_testrunner" ]
 
   data = [

test/unittests/heap/cppgc/stats-collector-scopes-unittest.cc

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#if !CPPGC_BUILD_IN_V8
+
 #include "src/heap/cppgc/stats-collector.h"
 #include "test/unittests/heap/cppgc/tests.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -300,3 +302,5 @@ TEST_F(CppgcTracingScopesTest, TestIndividualConcurrentScopes) {
 
 }  // namespace internal
 }  // namespace cppgc
+
+#endif  // !CPPGC_BUILD_IN_V8