[tools] Improve gcmole part II

Prepare gcmole.cc for the next update:
- Print possible GC locations when discovering stale/dead variables
- Make error messages less confusing for the modern V8 engineer
- Prepare gcmole to read suspects.allowlist instead of .whitelist
- Use more readable variable names
- Only log non-found types with --verbose
- Change the currently unusued gccauses format in gcmole.py and
  support loading it back in gcmole.cc
- Implemented first basic gc call-chain printing (disabled by default)

GCmole packaging:
- Add debug mode to bootstrap.sh build script
- Update gcmole.py run instructions in bootstrap.sh and package.sh

Bug: v8:10009
Change-Id: I369d48baa2980455d2e8f57e7a803d0384fe83f1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3480095Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79357}

src/wasm/c-api.cc

@@ -2293,12 +2293,20 @@ struct borrowed_vec {
 
 // Vectors
 
+#ifdef V8_GC_MOLE
+#define ASSERT_VEC_BASE_SIZE(name, Name, vec, ptr_or_none)
+
+#else
+#define ASSERT_VEC_BASE_SIZE(name, Name, vec, ptr_or_none)                 \
+  static_assert(sizeof(wasm_##name##_vec_t) == sizeof(vec<Name>),          \
+                "C/C++ incompatibility");                                  \
+  static_assert(                                                           \
+      sizeof(wasm_##name##_t ptr_or_none) == sizeof(vec<Name>::elem_type), \
+      "C/C++ incompatibility");
+#endif
+
 #define WASM_DEFINE_VEC_BASE(name, Name, vec, ptr_or_none)                     \
-  static_assert(sizeof(wasm_##name##_vec_t) == sizeof(vec<Name>),              \
-                "C/C++ incompatibility");                                      \
-  static_assert(                                                               \
-      sizeof(wasm_##name##_t ptr_or_none) == sizeof(vec<Name>::elem_type),     \
-      "C/C++ incompatibility");                                                \
+  ASSERT_VEC_BASE_SIZE(name, Name, vec, ptr_or_none)                           \
   extern "C++" inline auto hide_##name##_vec(vec<Name>& v)                     \
       ->wasm_##name##_vec_t* {                                                 \
     return reinterpret_cast<wasm_##name##_vec_t*>(&v);                         \

src/wasm/wasm-code-manager.h

@@ -495,7 +495,9 @@ class V8_EXPORT_PRIVATE WasmCode final {
 // often for rather small functions.
 // Increase the limit if needed, but first check if the size increase is
 // justified.
+#ifndef V8_GC_MOLE
 STATIC_ASSERT(sizeof(WasmCode) <= 88);
+#endif
 
 WasmCode::Kind GetCodeKind(const WasmCompilationResult& result);
 

tools/gcmole/Makefile

@@ -32,11 +32,18 @@ LLVM_BUILD_INCLUDE:=$(BUILD_ROOT)/include
 CLANG_SRC_INCLUDE:=$(CLANG_SRC_ROOT)/include
 CLANG_BUILD_INCLUDE:=$(BUILD_ROOT)/tools/clang/include
 
+CXXFLAGS = -O3 -g3
+all: libgcmole.so
+Release: libgcmole.so
+
+Debug: CXXFLAGS = -O1 -DDEBUG -g
+Debug: libgcmole.so
+
 libgcmole.so: gcmole.cc
 	$(CXX) -I$(LLVM_BUILD_INCLUDE) -I$(LLVM_SRC_INCLUDE)                  \
-	-I$(CLANG_BUILD_INCLUDE) -I$(CLANG_SRC_INCLUDE) -I. -D_DEBUG          \
+	-I$(CLANG_BUILD_INCLUDE) -I$(CLANG_SRC_INCLUDE) -I. ${CXXFLAGS}          \
 	-D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS         \
-	-D__STDC_LIMIT_MACROS -O3 -fomit-frame-pointer -fno-exceptions        \
+	-D__STDC_LIMIT_MACROS -fomit-frame-pointer -fno-exceptions        \
 	-fno-rtti -fPIC -Woverloaded-virtual -Wcast-qual -fno-strict-aliasing \
 	-pedantic -Wno-long-long -Wall -W -Wno-unused-parameter               \
 	-Wwrite-strings -static-libstdc++ -std=c++0x -shared -o libgcmole.so  \

tools/gcmole/README

@@ -109,7 +109,7 @@ script "bootstrap.sh" mentioned above).
 
 TROUBLESHOOTING ---------------------------------------------------------------
 
-gcmole is tighly coupled with the AST structure that Clang produces. Therefore
+gcmole is tightly coupled with the AST structure that Clang produces. Therefore
 when upgrading to a newer Clang version, it might start producing bogus output
 or completely stop outputting warnings. In such occasion, one might start the
 debugging process by checking weather a new AST node type is introduced which

tools/gcmole/bootstrap.sh

@@ -35,6 +35,8 @@
 
 LLVM_RELEASE=9.0.1
 
+BUILD_TYPE="Release"
+# BUILD_TYPE="Debug"
 THIS_DIR="$(readlink -f "$(dirname "${0}")")"
 LLVM_PROJECT_DIR="${THIS_DIR}/bootstrap/llvm"
 BUILD_DIR="${THIS_DIR}/bootstrap/build"
@@ -99,29 +101,35 @@ if [ ! -e "${BUILD_DIR}" ]; then
 fi
 cd "${BUILD_DIR}"
 cmake -GNinja -DCMAKE_CXX_FLAGS="-static-libstdc++" -DLLVM_ENABLE_TERMINFO=OFF \
-    -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS=clang \
+    -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DLLVM_ENABLE_PROJECTS=clang \
     -DLLVM_ENABLE_Z3_SOLVER=OFF "${LLVM_PROJECT_DIR}/llvm"
-MACOSX_DEPLOYMENT_TARGET=10.5 ninja -j"${NUM_JOBS}"
-
-# Strip the clang binary.
-STRIP_FLAGS=
-if [ "${OS}" = "Darwin" ]; then
-  # See http://crbug.com/256342
-  STRIP_FLAGS=-x
+MACOSX_DEPLOYMENT_TARGET=10.5 ninja -j"${NUM_JOBS}" clang
+
+if [[ "${BUILD_TYPE}" = "Release" ]]; then
+  # Strip the clang binary.
+  STRIP_FLAGS=
+  if [ "${OS}" = "Darwin" ]; then
+    # See http://crbug.com/256342
+    STRIP_FLAGS=-x
+  fi
+  strip ${STRIP_FLAGS} bin/clang
 fi
-strip ${STRIP_FLAGS} bin/clang
 cd -
 
 # Build libgcmole.so
 make -C "${THIS_DIR}" clean
 make -C "${THIS_DIR}" LLVM_SRC_ROOT="${LLVM_PROJECT_DIR}/llvm" \
     CLANG_SRC_ROOT="${LLVM_PROJECT_DIR}/clang" \
-    BUILD_ROOT="${BUILD_DIR}" libgcmole.so
+    BUILD_ROOT="${BUILD_DIR}" $BUILD_TYPE
 
 set +x
 
-echo
-echo You can now run gcmole using this command:
-echo
-echo CLANG_BIN=\"tools/gcmole/gcmole-tools/bin\" python tools/gcmole/gcmole.py
+echo '#########################################################################'
+echo 'Congratulations you compiled clang and libgcmole.so'
+echo 
+echo '# You can now run gcmole:'
+echo 'tools/gcmole/gcmole.py \'
+echo '   --clang-bin-dir="tools/gcmole/bootstrap/build/bin" \'
+echo '   --clang-plugins-dir="tools/gcmole" \'
+echo '   --v8-target-cpu=$CPU'
 echo

tools/gcmole/gcmole.cc

@@ -48,6 +48,8 @@ namespace {
 
 bool g_tracing_enabled = false;
 bool g_dead_vars_analysis = false;
+bool g_verbose = false;
+bool g_print_gc_call_chain = false;
 
 #define TRACE(str)                   \
   do {                               \
@@ -80,16 +82,13 @@ typedef std::map<MangledName, MangledName> CalleesMap;
 static bool GetMangledName(clang::MangleContext* ctx,
                            const clang::NamedDecl* decl,
                            MangledName* result) {
-  if (!llvm::isa<clang::CXXConstructorDecl>(decl) &&
-      !llvm::isa<clang::CXXDestructorDecl>(decl)) {
-    llvm::SmallVector<char, 512> output;
-    llvm::raw_svector_ostream out(output);
-    ctx->mangleName(decl, out);
-    *result = out.str().str();
-    return true;
-  }
-
-  return false;
+  if (llvm::isa<clang::CXXConstructorDecl>(decl)) return false;
+  if (llvm::isa<clang::CXXDestructorDecl>(decl)) return false;
+  llvm::SmallVector<char, 512> output;
+  llvm::raw_svector_ostream out(output);
+  ctx->mangleName(decl, out);
+  *result = out.str().str();
+  return true;
 }
 
 
@@ -217,8 +216,7 @@ struct Resolver {
 
 class CalleesPrinter : public clang::RecursiveASTVisitor<CalleesPrinter> {
  public:
-  explicit CalleesPrinter(clang::MangleContext* ctx) : ctx_(ctx) {
-  }
+  explicit CalleesPrinter(clang::MangleContext* ctx) : ctx_(ctx) {}
 
   virtual bool VisitCallExpr(clang::CallExpr* expr) {
     const clang::FunctionDecl* callee = expr->getDirectCallee();
@@ -236,17 +234,17 @@ class CalleesPrinter : public clang::RecursiveASTVisitor<CalleesPrinter> {
   }
 
   void AnalyzeFunction(const clang::FunctionDecl* f) {
+    if (!InV8Namespace(f)) return;
     MangledName name;
-    if (InV8Namespace(f) && GetMangledName(ctx_, f, &name)) {
-      const std::string& function = f->getNameAsString();
-      AddCallee(name, function);
-
-      const clang::FunctionDecl* body = NULL;
-      if (f->hasBody(body) && !Analyzed(name)) {
-        EnterScope(name);
-        TraverseStmt(body->getBody());
-        LeaveScope();
-      }
+    if (!GetMangledName(ctx_, f, &name)) return;
+    const std::string& function = f->getNameAsString();
+    AddCallee(name, function);
+
+    const clang::FunctionDecl* body = NULL;
+    if (f->hasBody(body) && !Analyzed(name)) {
+      EnterScope(name);
+      TraverseStmt(body->getBody());
+      LeaveScope();
     }
   }
 
@@ -303,17 +301,18 @@ class FunctionDeclarationFinder
     : public clang::ASTConsumer,
       public clang::RecursiveASTVisitor<FunctionDeclarationFinder> {
  public:
-  explicit FunctionDeclarationFinder(clang::DiagnosticsEngine& d,
-                                     clang::SourceManager& sm,
-                                     const std::vector<std::string>& args)
-      : d_(d), sm_(sm) {}
+  explicit FunctionDeclarationFinder(
+      clang::DiagnosticsEngine& diagnostics_engine,
+      clang::SourceManager& source_manager,
+      const std::vector<std::string>& args)
+      : diagnostics_engine_(diagnostics_engine),
+        source_manager_(source_manager) {}
 
   virtual void HandleTranslationUnit(clang::ASTContext &ctx) {
-    mangle_context_ = clang::ItaniumMangleContext::create(ctx, d_);
+    mangle_context_ =
+        clang::ItaniumMangleContext::create(ctx, diagnostics_engine_);
     callees_printer_ = new CalleesPrinter(mangle_context_);
-
     TraverseDecl(ctx.getTranslationUnitDecl());
-
     callees_printer_->PrintCallGraph();
   }
 
@@ -323,8 +322,8 @@ class FunctionDeclarationFinder
   }
 
  private:
-  clang::DiagnosticsEngine& d_;
-  clang::SourceManager& sm_;
+  clang::DiagnosticsEngine& diagnostics_engine_;
+  clang::SourceManager& source_manager_;
   clang::MangleContext* mangle_context_;
 
   CalleesPrinter* callees_printer_;
@@ -333,8 +332,39 @@ class FunctionDeclarationFinder
 static bool gc_suspects_loaded = false;
 static CalleesSet gc_suspects;
 static CalleesSet gc_functions;
-static bool whitelist_loaded = false;
-static CalleesSet suspects_whitelist;
+
+static bool allowlist_loaded = false;
+static CalleesSet suspects_allowlist;
+
+static bool gc_causes_loaded = false;
+static std::map<MangledName, std::vector<MangledName>> gc_causes;
+
+static void LoadGCCauses() {
+  if (gc_causes_loaded) return;
+  std::ifstream fin("gccauses");
+  std::string mangled, function;
+  while (!fin.eof()) {
+    std::getline(fin, mangled, ',');
+    std::getline(fin, function);
+    if (mangled.empty()) break;
+    std::string parent = mangled;
+    // start,nested
+    std::getline(fin, mangled, ',');
+    assert(mangled.compare("start") == 0);
+    std::getline(fin, function);
+    assert(function.compare("nested") == 0);
+    while (true) {
+      std::getline(fin, mangled, ',');
+      std::getline(fin, function);
+      if (mangled.compare("end") == 0) {
+        assert(function.compare("nested") == 0);
+        break;
+      }
+      gc_causes[parent].push_back(mangled);
+    }
+  }
+  gc_causes_loaded = true;
+}
 
 static void LoadGCSuspects() {
   if (gc_suspects_loaded) return;
@@ -352,55 +382,51 @@ static void LoadGCSuspects() {
   gc_suspects_loaded = true;
 }
 
-static void LoadSuspectsWhitelist() {
-  if (whitelist_loaded) return;
+static void LoadSuspectsAllowList() {
+  if (allowlist_loaded) return;
 
-  std::ifstream fin("tools/gcmole/suspects.whitelist");
+  // TODO(cbruni): clean up once fully migrated
+  std::ifstream fin("tools/gcmole/suspects.allowlist");
+  if (!fin.is_open()) {
+    fin = std::ifstream("tools/gcmole/suspects.whitelist");
+  }
   std::string s;
 
-  while (fin >> s) suspects_whitelist.insert(s);
+  while (fin >> s) suspects_allowlist.insert(s);
 
-  whitelist_loaded = true;
+  allowlist_loaded = true;
 }
 
 // Looks for exact match of the mangled name.
-static bool KnownToCauseGC(clang::MangleContext* ctx,
-                           const clang::FunctionDecl* decl) {
+static bool IsKnownToCauseGC(clang::MangleContext* ctx,
+                             const clang::FunctionDecl* decl) {
   LoadGCSuspects();
-
   if (!InV8Namespace(decl)) return false;
-
-  if (suspects_whitelist.find(decl->getNameAsString()) !=
-      suspects_whitelist.end()) {
+  if (suspects_allowlist.find(decl->getNameAsString()) !=
+      suspects_allowlist.end()) {
     return false;
   }
-
   MangledName name;
   if (GetMangledName(ctx, decl, &name)) {
     return gc_suspects.find(name) != gc_suspects.end();
   }
-
   return false;
 }
 
 // Looks for partial match of only the function name.
-static bool SuspectedToCauseGC(clang::MangleContext* ctx,
-                               const clang::FunctionDecl* decl) {
+static bool IsSuspectedToCauseGC(clang::MangleContext* ctx,
+                                 const clang::FunctionDecl* decl) {
   LoadGCSuspects();
-
   if (!InV8Namespace(decl)) return false;
-
-  LoadSuspectsWhitelist();
-  if (suspects_whitelist.find(decl->getNameAsString()) !=
-      suspects_whitelist.end()) {
+  LoadSuspectsAllowList();
+  if (suspects_allowlist.find(decl->getNameAsString()) !=
+      suspects_allowlist.end()) {
     return false;
   }
-
   if (gc_functions.find(decl->getNameAsString()) != gc_functions.end()) {
     TRACE_LLVM_DECL("Suspected by ", decl);
     return true;
   }
-
   return false;
 }
 
@@ -449,10 +475,9 @@ class ExprEffect {
   intptr_t effect_;
 };
 
-
-const std::string BAD_EXPR_MSG("Possible problem with evaluation order.");
-const std::string DEAD_VAR_MSG("Possibly dead variable.");
-
+const std::string BAD_EXPR_MSG(
+    "Possible problem with evaluation order with interleaved GCs.");
+const std::string DEAD_VAR_MSG("Possibly stale variable due to GCs.");
 
 class Environment {
  public:
@@ -612,22 +637,16 @@ class CallProps {
 
   ExprEffect ComputeCumulativeEffect(bool result_is_raw) {
     ExprEffect out = ExprEffect::NoneWithEnv(env_);
-    if (gc_.any()) {
-      out.setGC();
-    }
+    if (gc_.any()) out.setGC();
     if (raw_use_.any()) out.setRawUse();
     if (result_is_raw) out.setRawDef();
     return out;
   }
 
   bool IsSafe() {
-    if (!gc_.any()) {
-      return true;
-    }
+    if (!gc_.any()) return true;
     std::bitset<kMaxNumberOfArguments> raw = (raw_def_ | raw_use_);
-    if (!raw.any()) {
-      return true;
-    }
+    if (!raw.any()) return true;
     bool result = gc_.count() == 1 && !((raw ^ gc_).any());
     return result;
   }
@@ -950,13 +969,10 @@ class FunctionAnalyzer {
   ExprEffect Parallel(clang::Expr* parent, int n, clang::Expr** exprs,
                       const Environment& env) {
     CallProps props;
-
     for (int i = 0; i < n; ++i) {
       props.SetEffect(i, VisitExpr(exprs[i], env));
     }
-
     if (!props.IsSafe()) ReportUnsafe(parent, BAD_EXPR_MSG);
-
     return props.ComputeCumulativeEffect(
         RepresentsRawPointerType(parent->getType()));
   }
@@ -984,27 +1000,24 @@ class FunctionAnalyzer {
                  const clang::QualType& var_type,
                  const std::string& var_name,
                  const Environment& env) {
-    if (RepresentsRawPointerType(var_type)) {
-      // We currently care only about our internal pointer types and not about
-      // raw C++ pointers, because normally special care is taken when storing
-      // raw pointers to the managed heap. Furthermore, checking for raw
-      // pointers produces too many false positives in the dead variable
-      // analysis.
-      if (IsInternalPointerType(var_type) && !env.IsAlive(var_name) &&
-          !HasActiveGuard() && g_dead_vars_analysis) {
-        ReportUnsafe(parent, DEAD_VAR_MSG);
-      }
-      return ExprEffect::RawUse();
-    }
-    return ExprEffect::None();
+    if (!g_dead_vars_analysis) return ExprEffect::None();
+    if (!RepresentsRawPointerType(var_type)) return ExprEffect::None();
+    // We currently care only about our internal pointer types and not about
+    // raw C++ pointers, because normally special care is taken when storing
+    // raw pointers to the managed heap. Furthermore, checking for raw
+    // pointers produces too many false positives in the dead variable
+    // analysis.
+    if (!IsInternalPointerType(var_type)) return ExprEffect::None();
+    if (env.IsAlive(var_name)) return ExprEffect::None();
+    if (HasActiveGuard()) return ExprEffect::None();
+    ReportUnsafe(parent, DEAD_VAR_MSG);
+    return ExprEffect::RawUse();
   }
 
   ExprEffect Use(const clang::Expr* parent,
                  const clang::ValueDecl* var,
                  const Environment& env) {
-    if (IsExternalVMState(var)) {
-      return ExprEffect::GC();
-    }
+    if (IsExternalVMState(var)) return ExprEffect::GC();
     return Use(parent, var->getType(), var->getNameAsString(), env);
   }
 
@@ -1062,43 +1075,40 @@ class FunctionAnalyzer {
         RepresentsRawPointerType(call->getType()));
 
     clang::FunctionDecl* callee = call->getDirectCallee();
-    if (callee != NULL) {
-      if (KnownToCauseGC(ctx_, callee)) {
+    if (callee == NULL) return out;
+
+    if (IsKnownToCauseGC(ctx_, callee)) {
+      out.setGC();
+      scopes_.back().SetGCCauseLocation(
+          clang::FullSourceLoc(call->getExprLoc(), sm_), callee);
+    }
+
+    // Support for virtual methods that might be GC suspects.
+    if (memcall == NULL) return out;
+    clang::CXXMethodDecl* method =
+        llvm::dyn_cast_or_null<clang::CXXMethodDecl>(callee);
+    if (method == NULL) return out;
+    if (!method->isVirtual()) return out;
+
+    clang::CXXMethodDecl* target = method->getDevirtualizedMethod(
+        memcall->getImplicitObjectArgument(), false);
+    if (target != NULL) {
+      if (IsKnownToCauseGC(ctx_, target)) {
         out.setGC();
         scopes_.back().SetGCCauseLocation(
-            clang::FullSourceLoc(call->getExprLoc(), sm_));
+            clang::FullSourceLoc(call->getExprLoc(), sm_), target);
       }
-
-      // Support for virtual methods that might be GC suspects.
-      clang::CXXMethodDecl* method =
-          llvm::dyn_cast_or_null<clang::CXXMethodDecl>(callee);
-      if (method != NULL && method->isVirtual()) {
-        clang::CXXMemberCallExpr* memcall =
-            llvm::dyn_cast_or_null<clang::CXXMemberCallExpr>(call);
-        if (memcall != NULL) {
-          clang::CXXMethodDecl* target = method->getDevirtualizedMethod(
-              memcall->getImplicitObjectArgument(), false);
-          if (target != NULL) {
-            if (KnownToCauseGC(ctx_, target)) {
-              out.setGC();
-              scopes_.back().SetGCCauseLocation(
-                  clang::FullSourceLoc(call->getExprLoc(), sm_));
-            }
-          } else {
-            // According to the documentation, {getDevirtualizedMethod} might
-            // return NULL, in which case we still want to use the partial
-            // match of the {method}'s name against the GC suspects in order
-            // to increase coverage.
-            if (SuspectedToCauseGC(ctx_, method)) {
-              out.setGC();
-              scopes_.back().SetGCCauseLocation(
-                  clang::FullSourceLoc(call->getExprLoc(), sm_));
-            }
-          }
-        }
+    } else {
+      // According to the documentation, {getDevirtualizedMethod} might
+      // return NULL, in which case we still want to use the partial
+      // match of the {method}'s name against the GC suspects in order
+      // to increase coverage.
+      if (IsSuspectedToCauseGC(ctx_, method)) {
+        out.setGC();
+        scopes_.back().SetGCCauseLocation(
+            clang::FullSourceLoc(call->getExprLoc(), sm_), method);
       }
     }
-
     return out;
   }
 
@@ -1185,11 +1195,9 @@ class FunctionAnalyzer {
     }
 
     bool changed() {
-      if (changed_) {
-        changed_ = false;
-        return true;
-      }
-      return false;
+      if (!changed_) return false;
+      changed_ = false;
+      return true;
     }
 
     const Environment& in() {
@@ -1455,7 +1463,7 @@ class FunctionAnalyzer {
   }
 
   bool HasActiveGuard() {
-    for (auto s : scopes_) {
+    for (const auto s : scopes_) {
       if (s.IsBeforeGCCause()) return true;
     }
     return false;
@@ -1466,6 +1474,36 @@ class FunctionAnalyzer {
     d_.Report(clang::FullSourceLoc(expr->getExprLoc(), sm_),
               d_.getCustomDiagID(clang::DiagnosticsEngine::Warning, "%0"))
         << msg;
+    if (scopes_.empty()) return;
+    GCScope scope = scopes_[0];
+    if (!scope.gccause_location.isValid()) return;
+    d_.Report(scope.gccause_location,
+              d_.getCustomDiagID(clang::DiagnosticsEngine::Note,
+                                 "Call might cause unexpected GC."));
+    clang::FunctionDecl* gccause_decl = scope.gccause_decl;
+    d_.Report(
+        clang::FullSourceLoc(gccause_decl->getBeginLoc(), sm_),
+        d_.getCustomDiagID(clang::DiagnosticsEngine::Note, "GC call here."));
+
+    if (!g_print_gc_call_chain) return;
+    // TODO(cbruni, v8::10009): print call-chain to gc with proper source
+    // positions.
+    LoadGCCauses();
+    MangledName name;
+    if (!GetMangledName(ctx_, gccause_decl, &name)) return;
+    std::cout << "Potential GC call chain:\n";
+    std::set<MangledName> stack;
+    while (true) {
+      if (!stack.insert(name).second) break;
+      std::cout << "\t" << name << "\n";
+      auto next = gc_causes.find(name);
+      if (next == gc_causes.end()) break;
+      std::vector<MangledName> calls = next->second;
+      for (MangledName call : calls) {
+        name = call;
+        if (stack.find(call) != stack.end()) break;
+      }
+    }
   }
 
 
@@ -1484,10 +1522,11 @@ class FunctionAnalyzer {
   struct GCScope {
     clang::FullSourceLoc guard_location;
     clang::FullSourceLoc gccause_location;
+    clang::FunctionDecl* gccause_decl;
 
     // We're only interested in guards that are declared before any further GC
     // causing calls (see TestGuardedDeadVarAnalysisMidFunction for example).
-    bool IsBeforeGCCause() {
+    bool IsBeforeGCCause() const {
       if (!guard_location.isValid()) return false;
       if (!gccause_location.isValid()) return true;
       return guard_location.isBeforeInTranslationUnitThan(gccause_location);
@@ -1495,9 +1534,11 @@ class FunctionAnalyzer {
 
     // After we set the first GC cause in the scope, we don't need the later
     // ones.
-    void SetGCCauseLocation(clang::FullSourceLoc gccause_location_) {
+    void SetGCCauseLocation(clang::FullSourceLoc gccause_location_,
+                            clang::FunctionDecl* decl) {
       if (gccause_location.isValid()) return;
       gccause_location = gccause_location_;
+      gccause_decl = decl;
     }
   };
   std::vector<GCScope> scopes_;
@@ -1513,9 +1554,8 @@ class ProblemsFinder : public clang::ASTConsumer,
       if (args[i] == "--dead-vars") {
         g_dead_vars_analysis = true;
       }
-      if (args[i] == "--verbose") {
-        g_tracing_enabled = true;
-      }
+      if (args[i] == "--verbose-trace") g_tracing_enabled = true;
+      if (args[i] == "--verbose") g_verbose = true;
     }
   }
 
@@ -1571,7 +1611,7 @@ class ProblemsFinder : public clang::ASTConsumer,
           clang::ItaniumMangleContext::create(ctx, d_), object_decl,
           maybe_object_decl, smi_decl, no_gc_mole_decl, d_, sm_);
       TraverseDecl(ctx.getTranslationUnitDecl());
-    } else {
+    } else if (g_verbose) {
       if (object_decl == NULL) {
         llvm::errs() << "Failed to resolve v8::internal::Object\n";
       }
@@ -1609,7 +1649,6 @@ class ProblemsFinder : public clang::ASTConsumer,
   FunctionAnalyzer* function_analyzer_;
 };
 
-
 template<typename ConsumerType>
 class Action : public clang::PluginASTAction {
  protected:

tools/gcmole/gcmole.py

@@ -6,7 +6,6 @@
 # This is main driver for gcmole tool. See README for more details.
 # Usage: CLANG_BIN=clang-bin-dir python tools/gcmole/gcmole.py [arm|arm64|ia32|x64]
 
-
 # for py2/py3 compatibility
 from __future__ import print_function
 
@@ -14,13 +13,13 @@ from multiprocessing import cpu_count
 
 import collections
 import difflib
+import json
 import optparse
 import os
 import re
 import subprocess
 import sys
 import threading
-import json
 
 if sys.version_info.major > 2:
   from pathlib import Path
@@ -82,6 +81,15 @@ else:
 ArchCfg = collections.namedtuple(
     "ArchCfg", ["name", "cpu", "triple", "arch_define", "arch_options"])
 
+# TODO(cbruni): use gn desc by default for platform-specific settings
+OPTIONS_64BIT = [
+    "-DV8_COMPRESS_POINTERS",
+    "-DV8_COMPRESS_POINTERS_IN_SHARED_CAGE",
+    "-DV8_EXTERNAL_CODE_SPACE",
+    "-DV8_SHORT_BUILTIN_CALLS",
+    "-DV8_SHARED_RO_HEAP",
+]
+
 ARCHITECTURES = {
     "ia32":
         ArchCfg(
@@ -99,14 +107,15 @@ ARCHITECTURES = {
             arch_define="V8_TARGET_ARCH_ARM",
             arch_options=["-m32"],
         ),
+    # TODO(cbruni): Use detailed settings:
+    #   arch_options = OPTIONS_64BIT + [ "-DV8_WIN64_UNWINDING_INFO" ]
     "x64":
         ArchCfg(
             name="x64",
             cpu="x64",
             triple="x86_64-unknown-linux",
             arch_define="V8_TARGET_ARCH_X64",
-            arch_options=[],
-        ),
+            arch_options=[]),
     "arm64":
         ArchCfg(
             name="arm64",
@@ -148,7 +157,7 @@ def make_clang_command_line(plugin, plugin_args, options):
   icu_src_dir = options.v8_root_dir / 'third_party/icu/source'
   return ([
       options.clang_bin_dir / "clang++",
-      "-std=c++14",
+      "-std=c++17",
       "-c",
       "-Xclang",
       "-load",
@@ -164,11 +173,13 @@ def make_clang_command_line(plugin, plugin_args, options):
       "-Xclang",
       arch_cfg.triple,
       "-fno-exceptions",
+      "-Wno-everything",
       "-D",
       arch_cfg.arch_define,
       "-DENABLE_DEBUGGER_SUPPORT",
-      "-DV8_INTL_SUPPORT",
       "-DV8_ENABLE_WEBASSEMBLY",
+      "-DV8_GC_MOLE",
+      "-DV8_INTL_SUPPORT",
       "-I{}".format(options.v8_root_dir),
       "-I{}".format(options.v8_root_dir / 'include'),
       "-I{}".format(options.v8_build_dir / 'gen'),
@@ -253,7 +264,7 @@ def invoke_clang_plugin_for_each_file(filenames, plugin, plugin_args, options):
           else:
             break
         filename, returncode, stdout, stderr = output
-        log(filename, level=1)
+        log(filename, level=2)
         if returncode != 0:
           sys.stderr.write(stderr)
           sys.exit(returncode)
@@ -439,25 +450,44 @@ def generate_gc_suspects(files, options):
     collector.parse(stdout.splitlines())
   collector.propagate()
   # TODO(cbruni): remove once gcmole.cc is migrated
-  write_gc_suspects(collector, options.v8_root_dir)
-  write_gc_suspects(collector, options.out_dir)
-  log("GCSuspects generated for {}", options.v8_target_cpu)
-
-
-def write_gc_suspects(collector, dst):
+  write_gcmole_results(collector, options, options.v8_root_dir)
+  write_gcmole_results(collector, options, options.out_dir)
+
+
+def write_gcmole_results(collector, options, dst):
+  # gcsuspects contains a list("mangled_full_name,name") of all functions that
+  # could cause a gc (directly or indirectly).
+  #
+  # EXAMPLE
+  # _ZN2v88internal4Heap16CreateApiObjectsEv,CreateApiObjects
+  # _ZN2v88internal4Heap17CreateInitialMapsEv,CreateInitialMaps
+  # ...
   with open(dst / "gcsuspects", "w") as out:
-    for name, value in collector.gc.items():
+    for name, value in list(collector.gc.items()):
       if value:
         out.write(name + "\n")
-
+  # gccauses contains a map["mangled_full_name,name"] => list(inner gcsuspects)
+  # Where the inner gcsuspects are functions directly called in the outer
+  # function that can cause a gc. The format is encoded for simplified
+  # deserialization in gcmole.cc.
+  #
+  # EXAMPLE:
+  # _ZN2v88internal4Heap17CreateHeapObjectsEv,CreateHeapObjects
+  # start,nested
+  # _ZN2v88internal4Heap16CreateApiObjectsEv,CreateApiObjects
+  # _ZN2v88internal4Heap17CreateInitialMapsEv,CreateInitialMaps
+  # ...
+  # end,nested
+  # ...
   with open(dst / "gccauses", "w") as out:
-    out.write("GC = {\n")
-    for name, causes in collector.gc_caused.items():
-      out.write("  '{}': [\n".format(name))
+    for name, causes in list(collector.gc_caused.items()):
+      out.write("{}\n".format(name))
+      out.write("start,nested\n")
       for cause in causes:
-        out.write("    '{}',\n".format(cause))
-      out.write("  ],\n")
-    out.write("}\n")
+        out.write("{}\n".format(cause))
+      out.write("end,nested\n")
+  log("GCSuspects and gccauses generated for {} in '{}'", options.v8_target_cpu,
+      dst)
 
 
 # ------------------------------------------------------------------------------
@@ -498,7 +528,7 @@ def check_correctness_for_arch(options, for_test):
       sys.stdout.write(stderr)
 
   log("Done processing {} files.", processed_files)
-  log("Errors found" if errors_found else "## No errors found")
+  log("Errors found" if errors_found else "No errors found")
 
   return errors_found, output
 
@@ -598,7 +628,7 @@ def main(args):
   parser.add_option(
       "--out-dir",
       metavar="DIR",
-      help="Output location for gcsuspect and gcauses file."
+      help="Output location for the gcsuspect and gcauses file."
       "Default: BUILD_DIR/gen/tools/gcmole")
   parser.add_option(
       "--is-bot",
@@ -639,9 +669,9 @@ def main(args):
       action="store_true",
       default=True,
       dest="allowlist",
-      help="""When building gcsuspects allowlist certain functions as if they can be
-  causing GC. Currently used to reduce number of false positives in dead
-  variables analysis. See TODO for ALLOWLIST in gcmole.py""")
+      help="When building gcsuspects allowlist certain functions as if they can be "
+      "causing GC. Currently used to reduce number of false positives in dead "
+      "variables analysis. See TODO for ALLOWLIST in gcmole.py")
   group.add_option(
       "--test-run",
       action="store_true",

tools/gcmole/package.sh

@@ -14,6 +14,7 @@ PACKAGE_DIR="${THIS_DIR}/gcmole-tools"
 PACKAGE_FILE="${THIS_DIR}/gcmole-tools.tar.gz"
 PACKAGE_SUM="${THIS_DIR}/gcmole-tools.tar.gz.sha1"
 BUILD_DIR="${THIS_DIR}/bootstrap/build"
+V8_ROOT_DIR= `realpath "${THIS_DIR}/../.."`
 
 # Echo all commands
 set -x
@@ -72,5 +73,8 @@ echo "sudo chroot \$CHROOT_DIR bash -c 'PATH=/docs/depot_tools:\$PATH; /docs/v8/
 echo
 echo You can now run gcmole using this command:
 echo
-echo CLANG_BIN=\"tools/gcmole/gcmole-tools/bin\" python tools/gcmole/gcmole.py
+echo 'tools/gcmole/gcmole.py \'
+echo '   --clang-bin-dir="tools/gcmole/gcmole-tools/bin" \'
+echo '   --clang-plugins-dir="tools/gcmole/gcmole-tools" \'
+echo '   --v8-target-cpu=$CPU'
 echo