Add C++ Trace Event support to PPAPI/NaCl SDK

ppapi/cpp/dev/trace_event_dev.h

+// Copyright (c) 2013 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.
+
+#ifndef PPAPI_CPP_DEV_TRACE_EVENT_DEV_H_
+#define PPAPI_CPP_DEV_TRACE_EVENT_DEV_H_
+
+/// @file
+/// This file defines the API for Pepper plugins to add trace events.  Only
+/// <code>SetThreadName</code> is meant to be called directly by a developer,
+/// the other functions are only used by the macros in trace_event_internal.h.
+/// For details on how to instrument code, see:
+/// http://www.chromium.org/developers/how-tos/trace-event-profiling-tool/tracing-event-instrumentation
+namespace pp {

[brettw, 2013/02/15 19:21:59]

Blank line before this.

[elijahtaylor1, 2013/02/20 01:09:51]

Done.

+namespace trace_events {

[brettw, 2013/02/15 19:21:59]

In other places, we've had a C++ class following the C naming convention (so
this would be Trace_Events) with static classes inside it, rather than a nested
namespace.

Also, the interface in C should be PPB_TraceEvent_Dev (no underscore between
Trace and Event). We don't have to fix it in this patch, it but might be nice.

[elijahtaylor1, 2013/02/20 01:09:51]

Done.  Will roll a separate CL to rename Trace_Event -> TraceEvent for C and C++

+
+/// Sets the current thread's name.  This name will show up in trace captures in
+/// chrome://tracing
+void SetThreadName(const char* name);
+
+/// This function returns a pointer to a variable indicated if a particular
+/// category is enabled. See comments in trace_event_internal.h for more
+/// details.
+const unsigned char* GetCategoryEnabled(const char* category_name);
+
+/// Add a trace event entry.  See comments in trace_event_internal.h for more
+/// details.
+void AddTraceEvent(char phase,
+                   const unsigned char* category_enabled,
+                   const char* name,
+                   unsigned long long id,

[brettw, 2013/02/15 19:21:59]

This should match the type on the C interface (uint64_t). Same below.

[elijahtaylor1, 2013/02/20 01:09:51]

Done.  I kept the references below the same because they represent the interface
that the TRACE_EVENT macros expect (though I removed the "threshold" arguments
which don't exist anymore).

+                   int num_args,
+                   const char** arg_names,
+                   const unsigned char* arg_types,
+                   const unsigned long long* arg_values,
+                   unsigned char flags);
+
+}  // namespace trace_events
+}  // namespace pp
+
+// This header is modified from Chromium's base/debug/trace_event.h to provide
+// tracing through the PPB_Trace_Event_Dev interface.
+
+#define TRACE_EVENT_API_GET_CATEGORY_ENABLED \
+    pp::trace_events::GetCategoryEnabled
+
+// void TRACE_EVENT_API_ADD_TRACE_EVENT(
+//                    char phase,
+//                    const unsigned char* category_enabled,
+//                    const char* name,
+//                    unsigned long long id,
+//                    int num_args,
+//                    const char** arg_names,
+//                    const unsigned char* arg_types,
+//                    const unsigned long long* arg_values,
+//                    int threshold_begin_id,
+//                    long long threshold,
+//                    unsigned char flags)
+#define TRACE_EVENT_API_ADD_TRACE_EVENT pp::trace_events::AddTraceEvent
+
+// Defines atomic operations used internally by the tracing system.
+// Per comments in trace_event_internal.h these require no memory barrier,
+// and the Chromium gcc versions are defined as plain int load/store.
+#define TRACE_EVENT_API_ATOMIC_WORD intptr_t
+#define TRACE_EVENT_API_ATOMIC_LOAD(var) (var)
+#define TRACE_EVENT_API_ATOMIC_STORE(var, value) ((var) = (value))
+
+// Defines visibility for classes in trace_event_internal.h.
+#define TRACE_EVENT_API_CLASS_EXPORT
+
+#include "base/debug/trace_event_internal.h"
+
+#endif  // PPAPI_CPP_DEV_TRACE_EVENT_DEV_H_