Added a simple benchmark of wxLogDebug() and wxLogTrace().

Measure time taken by these calls when the debug/trace messages are not
enabled.

See #11829.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70434 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/benchmarks/log.cpp

@@ -0,0 +1,109 @@
+/////////////////////////////////////////////////////////////////////////////
+// Name:        tests/benchmarks/log.cpp
+// Purpose:     Log-related benchmarks
+// Author:      Vadim Zeitlin
+// Created:     2012-01-21
+// RCS-ID:      $Id$
+// Copyright:   (c) 2011 Vadim Zeitlin <vadim@wxwidgets.org>
+// Licence:     wxWindows licence
+/////////////////////////////////////////////////////////////////////////////
+
+#include "bench.h"
+
+#include "wx/log.h"
+
+// This class is used to check that the arguments of log functions are not
+// evaluated.
+struct NotCreated
+{
+    NotCreated() { wxAbort(); }
+
+    const char* AsStr() const { return "unreachable"; }
+};
+
+// Temporarily change the log level to the given one.
+class LogLevelSetter
+{
+public:
+    LogLevelSetter(wxLogLevel levelNew)
+        : m_levelOld(wxLog::GetLogLevel())
+    {
+        wxLog::SetLogLevel(levelNew);
+    }
+
+    ~LogLevelSetter()
+    {
+        wxLog::SetLogLevel(m_levelOld);
+    }
+
+private:
+    const wxLogLevel m_levelOld;
+
+    wxDECLARE_NO_COPY_CLASS(LogLevelSetter);
+};
+
+BENCHMARK_FUNC(LogDebugDisabled)
+{
+    LogLevelSetter level(wxLOG_Info);
+
+    wxLogDebug("Ignored debug message: %s", NotCreated().AsStr());
+
+    return true;
+}
+
+BENCHMARK_FUNC(LogTraceDisabled)
+{
+    LogLevelSetter level(wxLOG_Info);
+
+    wxLogTrace("", NotCreated().AsStr());
+
+    return true;
+}
+
+BENCHMARK_FUNC(LogTraceActive)
+{
+    static bool s_added = false;
+    if ( !s_added )
+    {
+        s_added = true;
+        wxLog::AddTraceMask("logbench");
+    }
+
+    // Remove the actual logging overhead by simply throwing away the log
+    // messages.
+    class NulLog : public wxLog
+    {
+    public:
+        NulLog()
+            : m_logOld(wxLog::SetActiveTarget(this))
+        {
+        }
+
+        virtual ~NulLog()
+        {
+            wxLog::SetActiveTarget(m_logOld);
+        }
+
+    protected:
+        virtual void DoLogRecord(wxLogLevel,
+                                 const wxString&,
+                                 const wxLogRecordInfo&)
+        {
+        }
+
+        wxLog* m_logOld;
+    };
+
+    NulLog nulLog;
+
+    wxLogTrace("logbench", "Trace message");
+
+    return true;
+}
+
+BENCHMARK_FUNC(LogTraceInactive)
+{
+    wxLogTrace("bloordyblop", "Trace message");
+
+    return true;
+}