[lsan] Ignore code comments

Code comments are heap-allocated and never freed. We don't want to
attach them to the code object via a finalizer, since that could change
gc timing and heap layout when you enable code comments. They are used
to testing only anyway, so leaking is acceptable here.

R=bmeurer@chromium.org, jarin@chromium.org

Bug: v8:7738
Change-Id: I27b0f95db1d66b57f4f113c154f23edb84e6700d
Reviewed-on: https://chromium-review.googlesource.com/1051241
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53107}

BUILD.gn

@@ -2040,6 +2040,7 @@ v8_source_set("v8_base") {
     "src/lookup-cache.h",
     "src/lookup.cc",
     "src/lookup.h",
+    "src/lsan.h",
     "src/machine-type.cc",
     "src/machine-type.h",
     "src/macro-assembler-inl.h",

src/compiler/code-assembler.cc

@@ -18,6 +18,7 @@
 #include "src/frames.h"
 #include "src/interface-descriptors.h"
 #include "src/interpreter/bytecodes.h"
+#include "src/lsan.h"
 #include "src/machine-type.h"
 #include "src/macro-assembler.h"
 #include "src/objects-inl.h"
@@ -500,6 +501,7 @@ void CodeAssembler::Comment(const char* format, ...) {
   const int prefix_len = 2;
   int length = builder.position() + 1;
   char* copy = reinterpret_cast<char*>(malloc(length + prefix_len));
+  LSAN_IGNORE_OBJECT(copy);
   MemCopy(copy + prefix_len, builder.Finalize(), length);
   copy[0] = ';';
   copy[1] = ' ';

src/compiler/code-generator.cc

@@ -13,6 +13,7 @@
 #include "src/compiler/wasm-compiler.h"
 #include "src/eh-frame.h"
 #include "src/frames.h"
+#include "src/lsan.h"
 #include "src/macro-assembler-inl.h"
 #include "src/optimized-compilation-info.h"
 
@@ -210,9 +211,9 @@ void CodeGenerator::AssembleCode() {
       current_block_ = block->rpo_number();
       unwinding_info_writer_.BeginInstructionBlock(tasm()->pc_offset(), block);
       if (FLAG_code_comments) {
-        // TODO(titzer): these code comments are a giant memory leak.
         Vector<char> buffer = Vector<char>::New(200);
         char* buffer_start = buffer.start();
+        LSAN_IGNORE_OBJECT(buffer_start);
 
         int next = SNPrintF(
             buffer, "-- B%d start%s%s%s%s", block->rpo_number().ToInt(),
@@ -712,7 +713,9 @@ void CodeGenerator::AssembleSourcePosition(SourcePosition source_position) {
       buffer << source_position.InliningStack(info);
     }
     buffer << " --";
-    tasm()->RecordComment(StrDup(buffer.str().c_str()));
+    char* str = StrDup(buffer.str().c_str());
+    LSAN_IGNORE_OBJECT(str);
+    tasm()->RecordComment(str);
   }
 }
 

src/lsan.h

@@ -0,0 +1,30 @@
+// Copyright 2018 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// LeakSanitizer support.
+
+#ifndef V8_LSAN_H_
+#define V8_LSAN_H_
+
+#include "src/base/macros.h"
+#include "src/globals.h"
+
+// There is no compile time flag for LSan, to enable this whenever ASan is
+// enabled. Note that LSan can be used as part of ASan with 'detect_leaks=1'.
+#ifdef V8_USE_ADDRESS_SANITIZER
+
+#include <sanitizer/lsan_interface.h>
+
+#define LSAN_IGNORE_OBJECT(ptr) __lsan_ignore_object(ptr)
+
+#else  // !V8_USE_ADDRESS_SANITIZER
+
+#define LSAN_IGNORE_OBJECT(ptr)                                                \
+  static_assert(std::is_pointer<decltype(ptr)>::value ||                       \
+                    std::is_same<v8::internal::Address, decltype(ptr)>::value, \
+                "static type violation")
+
+#endif  // V8_USE_ADDRESS_SANITIZER
+
+#endif  // V8_LSAN_H_

test/mjsunit/mjsunit.status

@@ -418,10 +418,6 @@
   # https://bugs.chromium.org/p/v8/issues/detail?id=7102
   # Flaky due to huge string allocation.
   'regress/regress-748069': [SKIP],
-
-  # https://crbug.com/v8/7738
-  # Code comments currently leak memory.
-  'code-comments': [SKIP],
 }],  # 'asan == True'
 
 ##############################################################################