Have all trace points emit to ETW.

base/debug/trace_event_win.h

Index: base/debug/trace_event_win.h
diff --git a/base/debug/trace_event_win.h b/base/debug/trace_event_win.h
index 2a900bb4314f055b67a24bfea4bcdc766a569424..725a8216e1c767f9cec0c5c54b0465f0554bb9dc 100644
--- a/base/debug/trace_event_win.h
+++ b/base/debug/trace_event_win.h
@@ -10,6 +10,7 @@
 
 #include "base/base_export.h"
 #include "base/debug/trace_event.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/win/event_trace_provider.h"
 
 // Fwd.
@@ -58,6 +59,27 @@ class BASE_EXPORT TraceEventETWProvider : public base::win::EtwTraceProvider {
     return Trace(name, -1, type, id, extra, -1);
   }
 
+  // Emit a trace. The event is defined by |category_group|, |name| and |type|.

[chrisha, 2013/09/09 16:41:12]

Emit a trace event.

[fdoray, 2013/09/09 19:38:59]

Done.

+  // |id| helps to identify related events.
+  // |thread_name| is the name of the thread that produced the event.
+  // |num_args| indicates the number of custom arguments to add to the trace.
+  // It must be <= |kTraceMaxNumArgs|. The names of the arguments are specified
+  // in |arg_names|. |arg_types| indicates how to interpret the value of
+  // each argument. Finally, the value of an argument is obtained from
+  // |convertable_values| if its type is TRACE_VALUE_TYPE_CONVERTABLE,
+  // from |arg_values| otherwise.
+  static void TraceWithArgs(
+      const char* category_group,
+      const char* name,
+      char type,
+      unsigned long long id,
+      const std::string& thread_name,
+      int num_args,
+      const char** arg_names,
+      const unsigned char* arg_types,
+      const unsigned long long* arg_values,
+      scoped_ptr<ConvertableToTraceFormat> convertable_values[]);
+
   // Retrieves the singleton.
   // Note that this may return NULL post-AtExit processing.
   static TraceEventETWProvider* GetInstance();
@@ -67,18 +89,6 @@ class BASE_EXPORT TraceEventETWProvider : public base::win::EtwTraceProvider {
     return enable_level() >= TRACE_LEVEL_INFORMATION;
   }
 
-  // Emit a trace of type |type| containing |name|, |id|, and |extra|.
-  // Note: |name| and |extra| must be NULL, or a zero-terminated string of
-  //    length |name_len| or |extra_len| respectively.
-  // Note: if name_len or extra_len are -1, the length of the corresponding
-  //    string will be used.
-  void TraceEvent(const char* name,
-                  size_t name_len,
-                  char type,
-                  const void* id,
-                  const char* extra,
-                  size_t extra_len);
-
   // Exposed for unittesting only, allows resurrecting our
   // singleton instance post-AtExit processing.
   static void Resurrect();
@@ -88,6 +98,36 @@ class BASE_EXPORT TraceEventETWProvider : public base::win::EtwTraceProvider {
   friend struct StaticMemorySingletonTraits<TraceEventETWProvider>;
   TraceEventETWProvider();
 
+  // Emit a trace.

[chrisha, 2013/09/09 16:41:12]

Emit a trace event.

[fdoray, 2013/09/09 19:38:59]

Done.

+  // It's possible to add up to |kTraceMaxNumArgs| custom arguments to
+  // the trace. |arg_values| and |arg_names| are arrays of |num_args| strings
+  // that indicate the names and values of the custom arguments.
+  // The payload of the produced trace follows this format:
+  // - Name (string)
+  // - Id (unsigned long long)
+  // - Category (string)
+  // - Thread name (string)
+  // - Name of parameter 1, or '\0' (string)
+  // - Value of parameter 1, or '\0' (string)
+  // - Name of parameter 2, or '\0' (string)
+  // - Value of parameter 2, or '\0' (string)
+  // If stack capture is enabled for the trace session:
+  // - Stack size (DWORD)
+  // - Stack pointers (stack size * void*)
+  // Strings are null-terminated and have a variable size.
+  //
+  // Note: |name| and |category_group| must be NULL, or a zero-terminated
+  //       string. The length of |name| must be specified by |name_len|.

[chrisha, 2013/09/09 16:41:12]

Why do we need to specify a name_len and not a category_goup len? Or
arg_names_lens? Curious about the inconsistency of the API.

[fdoray, 2013/09/09 19:38:59]

Done.

I initially kept the |name_len| parameter from the existing code. It allowed to
use the size() method instead of strlen() when a std::string was provided to the
ETW macros. Since ETW macros are going to disappear and are not used a lot in
the code, it's not necessary to keep this optimization. Macros from
trace_event.h don't accept std::string for the event name.

|thread_name| and |arg_values| are available as std::string in the caller, so I
use this type for the parameters to avoid a call to strlen(). The drawback of
this optimization is that the interface is not consistent (char* and
std::string). This method is not used directly by users of the tracing macros,
so I think it's OK. What do you think?

On 2013/09/09 16:41:12, chrisha wrote:

+  void TraceEvent(const char* category_group,
+                  const char* name,
+                  size_t name_len,
+                  char type,
+                  unsigned long long id,
+                  const std::string& thread_name,
+                  int num_args,
+                  const char** arg_names,
+                  std::string* arg_values);
+
   DISALLOW_COPY_AND_ASSIGN(TraceEventETWProvider);
 };