fix for MAINT-2147: crash in LLTextureCache::writeToFastCache on OSX

indra/llimage/llimage.cpp

@@ -666,8 +666,17 @@ void LLImageRaw::fill( const LLColor4U& color )
 	}
 }
 
+LLPointer<LLImageRaw> LLImageRaw::duplicate()
+{
+	if(getNumRefs() < 2)
+	{
+		return this; //nobody else refences to this image, no need to duplicate.
+	}
 
-
+	//make a duplicate
+	LLPointer<LLImageRaw> dup = new LLImageRaw(getData(), getWidth(), getHeight(), getComponents());
+	return dup; 
+}
 
 // Src and dst can be any size.  Src and dst can each have 3 or 4 components.
 void LLImageRaw::copy(LLImageRaw* src)

indra/llimage/llimage.h

@@ -30,6 +30,7 @@
 #include "lluuid.h"
 #include "llstring.h"
 #include "llthread.h"
+#include "llpointer.h"
 
 const S32 MIN_IMAGE_MIP =  2; // 4x4, only used for expand/contract power of 2
 const S32 MAX_IMAGE_MIP = 11; // 2048x2048
@@ -214,6 +215,9 @@ public:
 
 	// Copy operations
 	
+	//duplicate this raw image if refCount > 1.
+	LLPointer<LLImageRaw> duplicate();
+
 	// Src and dst can be any size.  Src and dst can each have 3 or 4 components.
 	void copy( LLImageRaw* src );
 

indra/newview/lltexturecache.cpp

@@ -1912,10 +1912,10 @@ bool LLTextureCache::writeToFastCache(S32 id, LLPointer<LLImageRaw> raw, S32 dis
 		h >>= i;
 		if(w * h *c > 0) //valid
 		{
-			LLPointer<LLImageRaw> newraw = new LLImageRaw(raw->getData(), raw->getWidth(), raw->getHeight(), raw->getComponents());
-			newraw->scale(w, h) ;
-			raw = newraw;
-
+			//make a duplicate to keep the original raw image untouched.
+			raw = raw->duplicate();
+			raw->scale(w, h) ;
+			
 			discardlevel += i ;
 		}
 	}

indra/newview/llviewertexture.cpp

@@ -1531,7 +1531,12 @@ void LLViewerFetchedTexture::addToCreateTexture()
 							destroyRawImage();
 							return ;
 						}
-						mRawImage->scale(w >> i, h >> i) ;					
+
+						{
+							//make a duplicate in case somebody else is using this raw image
+							mRawImage = mRawImage->duplicate(); 
+							mRawImage->scale(w >> i, h >> i) ;					
+						}
 					}
 				}
 			}
@@ -2899,7 +2904,11 @@ void LLViewerFetchedTexture::setCachedRawImage()
 				--i ;
 			}
 			
-			mRawImage->scale(w >> i, h >> i) ;
+			{
+				//make a duplicate in case somebody else is using this raw image
+				mRawImage = mRawImage->duplicate(); 
+				mRawImage->scale(w >> i, h >> i) ;
+			}
 		}
 		mCachedRawImage = mRawImage ;
 		mRawDiscardLevel += i ;