Rework QgsDebugMsgLevel to avoid construction of strings which

won't be logged at the current debug level Instead of always constructing debug strings, and then potentially ignoring them if they fall outside the current debug level, we instead rework the QgsDebugMsgLevel macro so that strings are only ever constructed when they WILL be logged. This avoids the (often very expensive) string construction for debug messages whenever the results won't be used. It allows low level (i.e. level 3 or 4) debug messages to be safely used without incurring huge slowdowns in debug builds. TODO: ensure we only ever use QgsDebugMsg() for ERROR reporting, and move all other debugging calls to QgsDebugMsgLevel instead. Credit for original idea goes to @wonder-sk!
qgis · Nov 25, 2019 · 65ad06d · 65ad06d
1 parent 529aea6
commit 65ad06d
Showing 1 changed file with 7 additions and 2 deletions.
diff --git a/src/core/qgslogger.h b/src/core/qgslogger.h
@@ -31,7 +31,7 @@ class QFile;
 
 #ifdef QGISDEBUG
 #define QgsDebugMsg(str) QgsLogger::debug(QString(str), 1, __FILE__, __FUNCTION__, __LINE__)
-#define QgsDebugMsgLevel(str, level) QgsLogger::debug(QString(str), (level), __FILE__, __FUNCTION__, __LINE__)
+#define QgsDebugMsgLevel(str, level) if ( level <= QgsLogger::debugLevel() ) { QgsLogger::debug(QString(str), (level), __FILE__, __FUNCTION__, __LINE__); }(void)(0)
 #define QgsDebugCall QgsScopeLogger _qgsScopeLogger(__FILE__, __FUNCTION__, __LINE__)
 #else
 #define QgsDebugCall
@@ -102,7 +102,12 @@ class CORE_EXPORT QgsLogger
     /**
      * Reads the environment variable QGIS_DEBUG and converts it to int. If QGIS_DEBUG is not set,
      the function returns 1 if QGISDEBUG is defined and 0 if not*/
-    static int debugLevel() { init(); return sDebugLevel; }
+    static int debugLevel()
+    {
+      if ( sDebugLevel == -999 )
+        init();
+      return sDebugLevel;
+    }
 
     //! Logs the message passed in to the logfile defined in QGIS_LOG_FILE if any. *
     static void logMessageToFile( const QString &message );