Make calling wxLog::IsAllowedTraceMask() safe during static init time.

Although using wxLog during statics initialization is not recommended, it may
still happen, possibly indirectly so make it work correctly by using an
accessor function for the array of trace masks which ensures that this array
is always correctly initialized before being used.

Closes #11592.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@63063 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/log.h

@@ -453,7 +453,7 @@ public:
 
     // get string trace masks: note that this is MT-unsafe if other threads can
     // call AddTraceMask() concurrently
-    static const wxArrayString& GetTraceMasks() { return ms_aTraceMasks; }
+    static const wxArrayString& GetTraceMasks();
 
     // sets the time stamp string format: this is used as strftime() format
     // string for the log targets which add time stamps to the messages; set
@@ -644,9 +644,6 @@ private:
 #if WXWIN_COMPATIBILITY_2_8
     static wxTraceMask ms_ulTraceMask;   // controls wxLogTrace behaviour
 #endif // WXWIN_COMPATIBILITY_2_8
-
-    // currently enabled trace masks
-    static wxArrayString ms_aTraceMasks;
 };
 
 // ----------------------------------------------------------------------------

src/common/log.cpp

@@ -106,7 +106,7 @@ wxLogRecords gs_bufferedLogRecords;
 // than main, i.e. it protects all accesses to gs_bufferedLogRecords above
 WX_DEFINE_LOG_CS(BackgroundLog);
 
-// this one is used for protecting ms_aTraceMasks from concurrent access
+// this one is used for protecting TraceMasks() from concurrent access
 WX_DEFINE_LOG_CS(TraceMask);
 
 // and this one is used for GetComponentLevels()
@@ -598,36 +598,67 @@ wxLogLevel wxLog::GetComponentLevel(wxString component)
 // wxLog trace masks
 // ----------------------------------------------------------------------------
 
+namespace
+{
+
+// because IsAllowedTraceMask() may be called during static initialization
+// (this is not recommended but it may still happen, see #11592) we can't use a
+// simple static variable which might be not initialized itself just yet to
+// store the trace masks, but need this accessor function which will ensure
+// that the variable is always correctly initialized before being accessed
+//
+// notice that this doesn't make accessing it MT-safe, of course, you need to
+// serialize accesses to it using GetTraceMaskCS() for this
+wxArrayString& TraceMasks()
+{
+    static wxArrayString s_traceMasks;
+
+    return s_traceMasks;
+}
+
+} // anonymous namespace
+
+/* static */ const wxArrayString& wxLog::GetTraceMasks()
+{
+    // because of this function signature (it returns a reference, not the
+    // object), it is inherently MT-unsafe so there is no need to acquire the
+    // lock here anyhow
+
+    return TraceMasks();
+}
+
 void wxLog::AddTraceMask(const wxString& str)
 {
     wxCRIT_SECT_LOCKER(lock, GetTraceMaskCS());
 
-    ms_aTraceMasks.push_back(str);
+    TraceMasks().push_back(str);
 }
 
 void wxLog::RemoveTraceMask(const wxString& str)
 {
     wxCRIT_SECT_LOCKER(lock, GetTraceMaskCS());
 
-    int index = ms_aTraceMasks.Index(str);
+    int index = TraceMasks().Index(str);
     if ( index != wxNOT_FOUND )
-        ms_aTraceMasks.RemoveAt((size_t)index);
+        TraceMasks().RemoveAt((size_t)index);
 }
 
 void wxLog::ClearTraceMasks()
 {
     wxCRIT_SECT_LOCKER(lock, GetTraceMaskCS());
 
-    ms_aTraceMasks.Clear();
+    TraceMasks().Clear();
 }
 
 /*static*/ bool wxLog::IsAllowedTraceMask(const wxString& mask)
 {
     wxCRIT_SECT_LOCKER(lock, GetTraceMaskCS());
 
-    for ( wxArrayString::iterator it = ms_aTraceMasks.begin(),
+    const wxArrayString& masks = GetTraceMasks();
-                                  en = ms_aTraceMasks.end();
+    for ( wxArrayString::const_iterator it = masks.begin(),
-         it != en; ++it )
+                                        en = masks.end();
+          it != en;
+          ++it )
     {
         if ( *it == mask)
             return true;
@@ -918,8 +949,6 @@ wxString        wxLog::ms_timestamp(wxS("%X"));  // time only, no date
 wxTraceMask     wxLog::ms_ulTraceMask  = (wxTraceMask)0;
 #endif // wxDEBUG_LEVEL
 
-wxArrayString   wxLog::ms_aTraceMasks;
-
 // ----------------------------------------------------------------------------
 // stdout error logging helper
 // ----------------------------------------------------------------------------