Index: Zend/Log/Formatter/Simple.php
===================================================================
--- Zend/Log/Formatter/Simple.php	(revision 10903)
+++ Zend/Log/Formatter/Simple.php	(working copy)
@@ -69,7 +69,12 @@
     {
         $output = $this->_format;
         foreach ($event as $name => $value) {
-            $output = str_replace("%$name%", $value, $output);
+            $placeholder = "%$name%";
+            // Don't try to cast values to strings unless a placeholder
+            // shows the data is expected.
+            if(strpos($output,$placeholder) !== false){
+                $output = str_replace($placeholder, $value, $output);
+            }
         }
         return $output;
     }
Index: Zend/Log/Formatter/Tracer.php
===================================================================
--- Zend/Log/Formatter/Tracer.php	(revision 0)
+++ Zend/Log/Formatter/Tracer.php	(revision 0)
@@ -0,0 +1,119 @@
+<?php
+/**
+ * Zend Framework
+ *
+ * LICENSE
+ *
+ * This source file is subject to the new BSD license that is bundled
+ * with this package in the file LICENSE.txt.
+ * It is also available through the world-wide-web at this URL:
+ * http://framework.zend.com/license/new-bsd
+ * If you did not receive a copy of the license and are unable to
+ * obtain it through the world-wide-web, please send an email
+ * to license@zend.com so we can send you a copy immediately.
+ *
+ * @category   Zend
+ * @package    Zend_Log
+ * @subpackage Formatter
+ * @copyright  Copyright (c) 2005-2008 Zend Technologies USA Inc. (http://www.zend.com)
+ * @license    http://framework.zend.com/license/new-bsd     New BSD License
+ * @version    $Id:$
+ */
+
+/** Zend_Log_Formatter_Interface */
+require_once 'Zend/Log/Formatter/Interface.php';
+
+/**
+ * @category   Zend
+ * @package    Zend_Log
+ * @subpackage Formatter
+ * @copyright  Copyright (c) 2005-2008 Zend Technologies USA Inc. (http://www.zend.com)
+ * @license    http://framework.zend.com/license/new-bsd     New BSD License
+ * @version    $Id$
+ */
+class Zend_Log_Formatter_Tracer implements Zend_Log_Formatter_Interface{
+	
+    const DEFAULT_FORMAT = '%timestamp% %priorityName% (%priority%): %message%';
+    const DEFAULT_FORMAT_TRACE =  ">%index%\t%file%:%line%\t(%class%::%function%)";       
+	/**
+     * Class constructor
+     *
+     * @param  null|string  $format  Format specifier for log messages
+     * @throws Zend_Log_Exception
+     */
+    public function __construct($format = null, $traceFormat = null)
+    {
+        if ($format === null) {
+            $format = self::DEFAULT_FORMAT . PHP_EOL;
+        }
+        if ($traceFormat === null) {
+            $traceFormat = self::DEFAULT_FORMAT_TRACE . PHP_EOL;
+        }
+
+        
+        if (! is_string($format)) {
+            throw new Zend_Log_Exception('Format must be a string');
+        }
+        if (! is_string($traceFormat)) {
+            throw new Zend_Log_Exception('Trace format must be a string');
+        }
+
+        $this->_format = $format;
+        $this->_traceFormat = $traceFormat;
+    }
+    
+    protected function formatBacktrace($trace){        
+        $text = '';        
+        // Avoid 'object', 'args', etc.
+        $names = array('index','file','line','class','function');        
+        
+        foreach($trace as $index => $level){
+            $level['index'] = $index;
+            $line = $this->_traceFormat;
+            foreach($names as $name){
+                $line = str_replace("%$name%", trim($level[$name]), $line);
+            }
+            $text .= $line;
+        }
+        return($text);        
+    }
+
+    protected function stringify($value){
+        if(is_array($value) || is_object($value)){                
+                ob_start();
+                print_r($value);
+                $rep = ob_get_clean();
+                return($rep);
+        }else{
+            return((string)$value);
+        }                
+    }
+
+    /**
+     * Formats data into a single line to be written by the writer.
+     *
+     * @param  array    $event    event data
+     * @return string             formatted line to write to the log
+     */
+    public function format($event)
+    {        
+        $output = $this->_format;
+        foreach ($event as $name => $value) {
+            $placeholder = "%$name%";            
+            // Don't try to cast values to strings unless a placeholder
+            // shows the data is expected.
+            if(strpos($output,$placeholder) !== false){               
+                $output = str_replace($placeholder, $this->stringify($value), $output);
+            }
+        }
+        
+        // Finally, treat the trace (if present) specially
+        if(array_key_exists('trace',$event)){
+            $trace = $this->formatBacktrace($event['trace']);
+            // $trace = preg_replace('/^/m',"\t",$trace); // Pad it out with tabs   
+            $output .= $trace.PHP_EOL;
+        }
+        return $output;
+    }
+    
+}
Index: Zend/Log.php
===================================================================
--- Zend/Log.php	(revision 10903)
+++ Zend/Log.php	(working copy)
@@ -62,6 +62,16 @@
     protected $_extras = array();
 
     /**
+     * A list of priorities where automatic backtracing is done for
+     * debugging purposes. A priority not in this list is by default
+     * assumed to be non-traced.
+     *
+     * @var array of priorities, keys are priority numbers, values
+     * are booleans.
+     */
+    protected $_tracedPriorities = array();
+
+    /**
      * Class constructor.  Create a new logger
      *
      * @param Zend_Log_Writer_Abstract|null  $writer  default writer
@@ -134,12 +144,16 @@
             throw new Zend_Log_Exception('Bad log priority');
         }
 
+        $traceData = $this->getBacktrace($priority);
+        
         // pack into event required by filters and writers
         $event = array_merge(array('timestamp'    => date('c'),
                                     'message'      => $message,
                                     'priority'     => $priority,
                                     'priorityName' => $this->_priorities[$priority]),
-                              $this->_extras);
+                              $traceData,
+                              $this->_extras
+        );
 
         // abort if rejected by the global filters
         foreach ($this->_filters as $filter) {
@@ -154,12 +168,55 @@
         }
     }
 
+    protected function getBacktrace($priority){
+        if(!(array_key_exists($priority,$this->_tracedPriorities) && ($this->_tracedPriorities[$priority]))){
+            // Not enabled for this priority
+            return(array());
+        }
+
+        $traceData = array();
+        // Get trace data
+        $fulltrace = debug_backtrace();
+
+        // Create a truncated copy that avoids Zend_Log* classes,  
+        $level = 0;
+        foreach ($fulltrace as $level => $details) {                      
+            if (!isset($details['class']) || (!preg_match('/^Zend_Log/',$details['class']))) {
+                break;
+            }
+        }
+        $num = max(0,($level-1));
+        $trace = array_slice($fulltrace,$num);
+            
+        // Find the file and line from the short copy
+        $line = $trace[0]['line'];
+        $file = $trace[0]['file'];
+            
+        // Find the calling info if there is a caller, otherwise current
+        $nextLevel = min(1,sizeof($trace));
+        $class    = $trace[$nextLevel]['class'];
+        $function = $trace[$nextLevel]['function'];
+
+            
+        // Note: Can not use setEventItem() or $_extras because
+        // those are persistent across events.
+            
+        $traceData['line'] = $line;
+        $traceData['file'] = $file;
+        $traceData['function'] = $function;
+        $traceData['class'] = $class;
+        $traceData['trace'] = $trace;
+        
+        return($traceData);
+
+    }
+
     /**
      * Add a custom priority
      *
      * @param  string   $name      Name of priority
      * @param  integer  $priority  Numeric priority
-     * @throws Zend_Log_InvalidArgumentException
+     * @throws Zend_Log_Exception
      */
     public function addPriority($name, $priority)
     {
@@ -177,6 +234,49 @@
     }
 
     /**
+     * Enables or disabled additional debug trace information for
+     * a given priority.
+     *
+     * @param integer $priority    Numeric priority
+     * @param boolean $enabled        True to enable extra tracing, false otherwise
+     */
+    public function setTracing($priority, $enabled){
+        if (! isset($this->_priorities[$priority])) {
+            /** @see Zend_Log_Exception */
+            require_once 'Zend/Log/Exception.php';
+            throw new Zend_Log_Exception('Bad log priority');
+        }
+        $this->_tracedPriorities[$priority] = $enabled;
+    }
+
+    /**
+     * Find out whether tracing is enabled or disabled for the given
+     * priority.
+     *
+     * @param integer $priority    Numeric priority
+     * @return boolean True if tracing is enabled, false otherwise.
+     */
+    public function getTracing($priority){
+        if (! isset($this->_priorities[$priority])) {
+            /** @see Zend_Log_Exception */
+            require_once 'Zend/Log/Exception.php';
+            throw new Zend_Log_Exception('Bad log priority');
+        }
+        if(array_key_exists($priority,$this->_tracedPriorities)){
+            return($this->_tracedPriorities[$priority]);
+        }else{
+            return(false);
+        }
+    }
+
+    /**
+     * Resets all tracing settings to off.
+     */
+    public function resetTracing(){
+        $this->_tracedPriorities = array();
+    }
+
+    /**
      * Add a filter that will be applied before all log writers.
      * Before a message will be received by any of the writers, it
      * must be accepted by all filters added with this method.