Don't do floating point assignment from uninitialized data, since it can crash. b=422011 r+sr=bzbarsky a=damon

layout/style/nsCSSValue.cpp

@@ -127,11 +127,17 @@ nsCSSValue::nsCSSValue(nsCSSValue::Image* aValue)
 nsCSSValue::nsCSSValue(const nsCSSValue& aCopy)
   : mUnit(aCopy.mUnit)
 {
-  if ((eCSSUnit_String <= mUnit) && (mUnit <= eCSSUnit_Attr)) {
+  if (mUnit <= eCSSUnit_Dummy) {
+    // nothing to do, but put this important case first
+  }
+  else if (eCSSUnit_Percent <= mUnit) {
+    mValue.mFloat = aCopy.mValue.mFloat;
+  }
+  else if (eCSSUnit_String <= mUnit && mUnit <= eCSSUnit_Attr) {
     mValue.mString = aCopy.mValue.mString;
     mValue.mString->AddRef();
   }
-  else if ((eCSSUnit_Integer <= mUnit) && (mUnit <= eCSSUnit_EnumColor)) {
+  else if (eCSSUnit_Integer <= mUnit && mUnit <= eCSSUnit_EnumColor) {
     mValue.mInt = aCopy.mValue.mInt;
   }
   else if (eCSSUnit_Color == mUnit) {
@@ -150,7 +156,7 @@ nsCSSValue::nsCSSValue(const nsCSSValue& aCopy)
     mValue.mImage->AddRef();
   }
   else {
-    mValue.mFloat = aCopy.mValue.mFloat;
+    NS_NOTREACHED("unknown unit");
   }
 }
 
@@ -166,7 +172,7 @@ nsCSSValue& nsCSSValue::operator=(const nsCSSValue& aCopy)
 PRBool nsCSSValue::operator==(const nsCSSValue& aOther) const
 {
   if (mUnit == aOther.mUnit) {
-    if (mUnit <= eCSSUnit_System_Font) {
+    if (mUnit <= eCSSUnit_Dummy) {
       return PR_TRUE;
     }
     else if ((eCSSUnit_String <= mUnit) && (mUnit <= eCSSUnit_Attr)) {

layout/style/nsCSSValue.h

@@ -138,7 +138,7 @@ public:
   explicit nsCSSValue(nsCSSUnit aUnit = eCSSUnit_Null)
     : mUnit(aUnit)
   {
-    NS_ASSERTION(aUnit <= eCSSUnit_System_Font, "not a valueless unit");
+    NS_ASSERTION(aUnit <= eCSSUnit_Dummy, "not a valueless unit");
   }
 
   nsCSSValue(PRInt32 aValue, nsCSSUnit aUnit) NS_HIDDEN;