crashtesting: threaded scaling crash on re-export of ooo24840-1.sxw to odt

#13 0x00007f1cb843752a in o3tl::cow_wrapper<ImplBitmapPalette, o3tl::UnsafeRefCountingPolicy>::operator->() (this=0x5596086d5968) at include/o3tl/cow_wrapper.hxx:329
__PRETTY_FUNCTION__ = "BitmapColor& BitmapPalette::operator[](sal_uInt16)"
#14 0x00007f1cb843752a in BitmapPalette::operator[](unsigned short) (this=0x5596086d5968, nIndex=nIndex@entry=0) at vcl/source/bitmap/bitmappalette.cxx:139
__PRETTY_FUNCTION__ = "BitmapColor& BitmapPalette::operator[](sal_uInt16)"
#15 0x00007f1cb849f5f5 in BitmapInfoAccess::GetPaletteColor(unsigned short) const (nColor=0, this=0x5596085989f0) at include/vcl/BitmapInfoAccess.hxx:114
__PRETTY_FUNCTION__ = "const BitmapColor& BitmapInfoAccess::GetPaletteColor(sal_uInt16) const"

the mpBuffer member of BitmapInfoAccess is

BitmapBuffer* mpBuffer;

not

const BitmapBuffer* mpBuffer;

so mpBuffer->maPalette.foo() calls non-const variants of foo(),
(BitmapPalette::operator[](unsigned short) in this case), which
is presumably non the expected outcome, as the copy-on-write mpImpl of
BitmapPalette unsafely creates a new copy its internals on the first
dereference of mpImpl in a non-const method.

Change-Id: I1ebb3c67386a9028e5b8bab4b2d1cc5862700aa1
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/121917
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>

2 files changed, 27 insertions, 12 deletions

diff --git a/include/vcl/bitmapaccess.hxx b/include/vcl/bitmapaccess.hxx
index 12304d96ff86..559b5c7a3c02 100644
--- a/include/vcl/bitmapaccess.hxx
+++ b/include/vcl/bitmapaccess.hxx
@@ -96,31 +96,39 @@ public:
 
     bool HasPalette() const
     {
-        assert(mpBuffer && "Access is not valid!");
+        const BitmapBuffer* pBuffer = mpBuffer;
+
+        assert(pBuffer && "Access is not valid!");
 
-        return mpBuffer && !!mpBuffer->maPalette;
+        return pBuffer && !!pBuffer->maPalette;
     }
 
     const BitmapPalette& GetPalette() const
     {
-        assert(mpBuffer && "Access is not valid!");
+        const BitmapBuffer* pBuffer = mpBuffer;
 
-        return mpBuffer->maPalette;
+        assert(pBuffer && "Access is not valid!");
+
+        return pBuffer->maPalette;
     }
 
     sal_uInt16 GetPaletteEntryCount() const
     {
+        const BitmapBuffer* pBuffer = mpBuffer;
+
         assert(HasPalette() && "Bitmap has no palette!");
 
-        return HasPalette() ? mpBuffer->maPalette.GetEntryCount() : 0;
+        return HasPalette() ? pBuffer->maPalette.GetEntryCount() : 0;
     }
 
     const BitmapColor& GetPaletteColor( sal_uInt16 nColor ) const
     {
-        assert(mpBuffer && "Access is not valid!");
+        const BitmapBuffer* pBuffer = mpBuffer;
+
+        assert(pBuffer && "Access is not valid!");
         assert(HasPalette() && "Bitmap has no palette!");
 
-        return mpBuffer->maPalette[nColor];
+        return pBuffer->maPalette[nColor];
     }
 
     const BitmapColor& GetBestPaletteColor(const BitmapColor& rBitmapColor) const
@@ -130,11 +138,13 @@ public:
 
     sal_uInt16 GetBestPaletteIndex(const BitmapColor& rBitmapColor) const;
 
-    ColorMask& GetColorMask() const
+    const ColorMask& GetColorMask() const
     {
-        assert(mpBuffer && "Access is not valid!");
+        const BitmapBuffer* pBuffer = mpBuffer;
+
+        assert(pBuffer && "Access is not valid!");
 
-        return mpBuffer->maColorMask;
+        return pBuffer->maColorMask;
     }
 
 private:
@@ -207,7 +217,10 @@ public:
     BitmapColor GetColor(tools::Long nY, tools::Long nX) const
     {
         if (HasPalette())
-            return mpBuffer->maPalette[GetPixelIndex(nY, nX)];
+        {
+            const BitmapBuffer* pBuffer = mpBuffer;
+            return pBuffer->maPalette[GetPixelIndex(nY, nX)];
+        }
         else
             return GetPixel(nY, nX);
     }
diff --git a/vcl/source/gdi/bmpacc.cxx b/vcl/source/gdi/bmpacc.cxx
index 18c5769678c5..9c418a374e33 100644
--- a/vcl/source/gdi/bmpacc.cxx
+++ b/vcl/source/gdi/bmpacc.cxx
@@ -79,7 +79,9 @@ BitmapInfoAccess::~BitmapInfoAccess()
 
 sal_uInt16 BitmapInfoAccess::GetBestPaletteIndex( const BitmapColor& rBitmapColor ) const
 {
-    return( HasPalette() ? mpBuffer->maPalette.GetBestIndex( rBitmapColor ) : 0 );
+    const BitmapBuffer* pBuffer = mpBuffer;
+
+    return( HasPalette() ? pBuffer->maPalette.GetBestIndex( rBitmapColor ) : 0 );
 }
 
 BitmapReadAccess::BitmapReadAccess( Bitmap& rBitmap, BitmapAccessMode nMode ) :