[Tracing] Minor bugs fix.

1. The third parameter of strncpy should be the length of source string.
2. Value contains " should be valid.

BUG=v8:4561

Review-Url: https://codereview.chromium.org/2232683002
Cr-Commit-Position: refs/heads/master@{#38563}

src/libplatform/tracing/trace-object.cc

@@ -21,12 +21,12 @@ V8_INLINE static size_t GetAllocLength(const char* str) {
 // Copies |*member| into |*buffer|, sets |*member| to point to this new
 // location, and then advances |*buffer| by the amount written.
 V8_INLINE static void CopyTraceObjectParameter(char** buffer,
-                                               const char** member,
-                                               const char* end) {
+                                               const char** member) {
   if (*member) {
-    strncpy(*buffer, *member, end - *buffer);
+    size_t length = strlen(*member) + 1;
+    strncpy(*buffer, *member, length);
     *member = *buffer;
-    *buffer += strlen(*member) + 1;
+    *buffer += length;
   }
 }
 
@@ -81,17 +81,16 @@ void TraceObject::Initialize(char phase, const uint8_t* category_enabled_flag,
     // to free old memory.
     delete[] parameter_copy_storage_;
     char* ptr = parameter_copy_storage_ = new char[alloc_size];
-    const char* end = ptr + alloc_size;
     if (copy) {
-      CopyTraceObjectParameter(&ptr, &name_, end);
-      CopyTraceObjectParameter(&ptr, &scope_, end);
+      CopyTraceObjectParameter(&ptr, &name_);
+      CopyTraceObjectParameter(&ptr, &scope_);
       for (int i = 0; i < num_args_; ++i) {
-        CopyTraceObjectParameter(&ptr, &arg_names_[i], end);
+        CopyTraceObjectParameter(&ptr, &arg_names_[i]);
       }
     }
     for (int i = 0; i < num_args_; ++i) {
       if (arg_is_copy[i]) {
-        CopyTraceObjectParameter(&ptr, &arg_values_[i].as_string, end);
+        CopyTraceObjectParameter(&ptr, &arg_values_[i].as_string);
       }
     }
   }

src/libplatform/tracing/trace-writer.cc

@@ -15,11 +15,11 @@ namespace tracing {
 
 // Currently we do not support JSON-escaping strings in trace arguments.
 // Thus we perform an IsJSONString() check before writing any string argument.
-// In particular, this means strings cannot have control characters or " or \.
+// In particular, this means strings cannot have control characters or \.
 V8_INLINE static bool IsJSONString(const char* str) {
   size_t len = strlen(str);
   for (size_t i = 0; i < len; ++i) {
-    if (iscntrl(str[i]) || str[i] == '\"' || str[i] == '\\') {
+    if (iscntrl(str[i]) || str[i] == '\\') {
       return false;
     }
   }
@@ -74,8 +74,8 @@ void JSONTraceWriter::AppendArgValue(uint8_t type,
     case TRACE_VALUE_TYPE_COPY_STRING:
       // Strings are currently not JSON-escaped, so we need to perform a check
       // to see if they are valid JSON strings.
-      CHECK(value.as_string == nullptr || IsJSONString(value.as_string));
-      stream_ << "\"" << (value.as_string ? value.as_string : "NULL") << "\"";
+      CHECK(value.as_string != nullptr && IsJSONString(value.as_string));
+      stream_ << (value.as_string ? value.as_string : "NULL");
       break;
     default:
       UNREACHABLE();

test/cctest/libplatform/test-tracing.cc

@@ -217,8 +217,9 @@ TEST(TestTracingControllerMultipleArgsAndCopy) {
   double jj4 = std::numeric_limits<double>::infinity();
   double jj5 = -std::numeric_limits<double>::infinity();
   void* kk = &aa;
-  const char* ll = "100";
+  const char* ll = "\"100\"";
   std::string mm = "INIT";
+  std::string mmm = "\"INIT\"";
 
   // Create a scope for the tracing controller to terminate the trace writer.
   {
@@ -250,19 +251,20 @@ TEST(TestTracingControllerMultipleArgsAndCopy) {
     TRACE_EVENT1("v8", "v8.Test.jj5", "jj5", jj5);
     TRACE_EVENT1("v8", "v8.Test.kk", "kk", kk);
     TRACE_EVENT1("v8", "v8.Test.ll", "ll", ll);
-    TRACE_EVENT1("v8", "v8.Test.mm", "mm", TRACE_STR_COPY(mm.c_str()));
+    TRACE_EVENT1("v8", "v8.Test.mm", "mm", TRACE_STR_COPY(mmm.c_str()));
 
     TRACE_EVENT2("v8", "v8.Test2.1", "aa", aa, "ll", ll);
-    TRACE_EVENT2("v8", "v8.Test2.2", "mm1", TRACE_STR_COPY(mm.c_str()), "mm2",
-                 TRACE_STR_COPY(mm.c_str()));
+    TRACE_EVENT2("v8", "v8.Test2.2", "mm1", TRACE_STR_COPY(mmm.c_str()), "mm2",
+                 TRACE_STR_COPY(mmm.c_str()));
 
     // Check copies are correct.
     TRACE_EVENT_COPY_INSTANT0("v8", mm.c_str(), TRACE_EVENT_SCOPE_THREAD);
     TRACE_EVENT_COPY_INSTANT1("v8", mm.c_str(), TRACE_EVENT_SCOPE_THREAD,
-                              mm.c_str(), mm.c_str());
+                              mm.c_str(), mmm.c_str());
     TRACE_EVENT_COPY_INSTANT2("v8", mm.c_str(), TRACE_EVENT_SCOPE_THREAD,
-                              mm.c_str(), mm.c_str(), mm.c_str(), mm.c_str());
+                              mm.c_str(), mmm.c_str(), mm.c_str(), mmm.c_str());
     mm = "CHANGED";
+    mmm = "CHANGED";
 
     tracing_controller.StopTracing();
   }