Non-US OS region generates invalid trace JSON.

base/debug/trace_event_impl.cc

 // Copyright (c) 2012 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.
 
 #include "base/debug/trace_event_impl.h"
 
 #include <algorithm>
 
 #include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/leak_annotations.h"
 #include "base/debug/trace_event.h"
 #include "base/format_macros.h"
 #include "base/lazy_instance.h"
 #include "base/memory/singleton.h"
 #include "base/message_loop/message_loop.h"
 #include "base/process/process_metrics.h"
 #include "base/stl_util.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_tokenizer.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/synchronization/cancellation_flag.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/sys_info.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
 #include "base/threading/platform_thread.h"
@@ skipping 472 matching lines @@
   switch (type) {
     case TRACE_VALUE_TYPE_BOOL:
       *out += value.as_bool ? "true" : "false";
       break;
     case TRACE_VALUE_TYPE_UINT:
       StringAppendF(out, "%" PRIu64, static_cast<uint64>(value.as_uint));
       break;
     case TRACE_VALUE_TYPE_INT:
       StringAppendF(out, "%" PRId64, static_cast<int64>(value.as_int));
       break;
-    case TRACE_VALUE_TYPE_DOUBLE:
-      StringAppendF(out, "%f", value.as_double);
+    case TRACE_VALUE_TYPE_DOUBLE: {
+      std::string real = DoubleToString(value.as_double);

[dsinclair, 2013/10/07 14:26:51]

Can we add a TODO in here since this is the same as the code in
base/json/json_writer.cc to make a common method?

[Erik Dahlström (inactive), 2013/10/07 15:00:52]

Done.

+      // Ensure that the number has a .0 if there's no decimal or 'e'.  This
+      // makes sure that when we read the JSON back, it's interpreted as a
+      // real rather than an int.
+      if (real.find('.') == std::string::npos &&
+          real.find('e') == std::string::npos &&
+          real.find('E') == std::string::npos) {
+        real.append(".0");
+      }
+      // The JSON spec requires that non-integer values in the range (-1,1)
+      // have a zero before the decimal point - ".52" is not valid, "0.52" is.
+      if (real[0] == '.') {
+        real.insert(0, "0");
+      } else if (real.length() > 1 && real[0] == '-' && real[1] == '.') {
+        // "-.1" bad "-0.1" good
+        real.insert(1, "0");
+      }
+
+      StringAppendF(out, "%s", real.c_str());
       break;
+    }
     case TRACE_VALUE_TYPE_POINTER:
       // JSON only supports double and int numbers.
       // So as not to lose bits from a 64-bit pointer, output as a hex string.
       StringAppendF(out, "\"0x%" PRIx64 "\"", static_cast<uint64>(
                                      reinterpret_cast<intptr_t>(
                                      value.as_pointer)));
       break;
     case TRACE_VALUE_TYPE_STRING:
     case TRACE_VALUE_TYPE_COPY_STRING:
       *out += "\"";
@@ skipping 1545 matching lines @@
         0,                       // num_args
         NULL,                    // arg_names
         NULL,                    // arg_types
         NULL,                    // arg_values
         NULL,                    // convertable values
         TRACE_EVENT_FLAG_NONE);  // flags
   }
 }
 
 }  // namespace trace_event_internal