diff --git a/mozilla/layout/mathml/base/src/nsMathMLFrame.cpp b/mozilla/layout/mathml/base/src/nsMathMLFrame.cpp
index 08b5f527659..9e0fb0a9655 100644
--- a/mozilla/layout/mathml/base/src/nsMathMLFrame.cpp
+++ b/mozilla/layout/mathml/base/src/nsMathMLFrame.cpp
@@ -468,7 +468,7 @@ nsMathMLFrame::ParseNamedSpaceValue(nsIFrame*   aMathMLmstyleFrame,
 
   // See if it is one of the 'namedspace' (ranging 1/18em...7/18em)
   PRInt32 i = 0;
-  nsIAtom* namedspaceAtom;
+  nsIAtom* namedspaceAtom = nsnull;
   if (aString.Equals(NS_LITERAL_STRING("veryverythinmathspace"))) {
     i = 1;
     namedspaceAtom = nsMathMLAtoms::veryverythinmathspace_;
diff --git a/mozilla/layout/mathml/base/src/nsMathMLmfencedFrame.cpp b/mozilla/layout/mathml/base/src/nsMathMLmfencedFrame.cpp
index eb835400a93..09d34c6a17a 100644
--- a/mozilla/layout/mathml/base/src/nsMathMLmfencedFrame.cpp
+++ b/mozilla/layout/mathml/base/src/nsMathMLmfencedFrame.cpp
@@ -129,7 +129,7 @@ nsMathMLmfencedFrame::CreateFencesAndSeparators(nsIPresContext* aPresContext)
 {
   nsresult rv;
   nsAutoString value, data;
-  PRBool isMutable;
+  PRBool isMutable = PR_FALSE;
 
   //////////////  
   // see if the opening fence is there ...
@@ -142,7 +142,7 @@ nsMathMLmfencedFrame::CreateFencesAndSeparators(nsIPresContext* aPresContext)
   else if (NS_CONTENT_ATTR_NOT_THERE == rv)
     data = PRUnichar('('); // default as per the MathML REC
   else
-    data = nsAutoString();
+    data.Truncate();
 
   if (0 < data.Length()) {
     mOpenChar = new nsMathMLChar;
@@ -163,7 +163,7 @@ nsMathMLmfencedFrame::CreateFencesAndSeparators(nsIPresContext* aPresContext)
   else if (NS_CONTENT_ATTR_NOT_THERE == rv)
     data = PRUnichar(')'); // default as per the MathML REC
   else
-    data = nsAutoString();
+    data.Truncate();
 
   if (0 < data.Length()) {
     mCloseChar = new nsMathMLChar;
@@ -184,16 +184,11 @@ nsMathMLmfencedFrame::CreateFencesAndSeparators(nsIPresContext* aPresContext)
   else if (NS_CONTENT_ATTR_NOT_THERE == rv)
     data = PRUnichar(','); // default as per the MathML REC
   else
-    data = nsAutoString();
+    data.Truncate();
 
   mSeparatorsCount = data.Length();
   if (0 < mSeparatorsCount) {
-    PRInt32 sepCount = -1;
-    nsIFrame* childFrame = mFrames.FirstChild();
-    while (childFrame) {
-      sepCount++;
-      childFrame->GetNextSibling(&childFrame);
-    }
+    PRInt32 sepCount = mFrames.GetLength() - 1;
     if (0 < sepCount) {
       mSeparatorsChar = new nsMathMLChar[sepCount];
       if (!mSeparatorsChar) return NS_ERROR_OUT_OF_MEMORY;
diff --git a/mozilla/layout/mathml/base/src/nsMathMLmpaddedFrame.cpp b/mozilla/layout/mathml/base/src/nsMathMLmpaddedFrame.cpp
index 5a75ee12376..9e5adc7a616 100644
--- a/mozilla/layout/mathml/base/src/nsMathMLmpaddedFrame.cpp
+++ b/mozilla/layout/mathml/base/src/nsMathMLmpaddedFrame.cpp
@@ -294,7 +294,7 @@ nsMathMLmpaddedFrame::UpdateValue(nsIPresContext*      aPresContext,
   nsCSSUnit unit = aCSSValue.GetUnit();
   if (NS_MATHML_SIGN_INVALID != aSign && eCSSUnit_Null != unit) 
   {
-    nscoord scaler, amount;
+    nscoord scaler = 0, amount = 0;
 
     if (eCSSUnit_Percent == unit || eCSSUnit_Number == unit) 
     {