Replace qAllocMore with a pair of more useful functions

The first is "exact", not "more": qCalculateBlockSize. It ensures that
there's no overflow in multiplying, adding the header size or when
converting back to an int.

The second is the replacement for qAllocMore: it calculates the block
size like the first, but increases the block size to accommodate future
appends. The number of elements that fit in the block is also returned.

Task-number: QTBUG-41230
Change-Id: I52dd43c12685407bb9a6ffff13f5da09f816e667
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 3 insertions, 6 deletions

diff --git a/src/gui/text/qfragmentmap_p.h b/src/gui/text/qfragmentmap_p.h
index 4cf17aadc7..b54d7261d0 100644
--- a/src/gui/text/qfragmentmap_p.h
+++ b/src/gui/text/qfragmentmap_p.h
@@ -255,14 +255,11 @@ uint QFragmentMapData<Fragment>::createFragment()
     uint freePos = head->freelist;
     if (freePos == head->allocated) {
         // need to create some free space
-        if (freePos >= uint(MaxAllocSize) / fragmentSize)
-            qBadAlloc();
-        uint needed = qAllocMore((freePos+1)*fragmentSize, 0);
-        Q_ASSERT(needed/fragmentSize > head->allocated);
-        Fragment *newFragments = (Fragment *)realloc(fragments, needed);
+        auto blockInfo = qCalculateGrowingBlockSize(freePos + 1, fragmentSize);
+        Fragment *newFragments = (Fragment *)realloc(fragments, blockInfo.size);
         Q_CHECK_PTR(newFragments);
         fragments = newFragments;
-        head->allocated = needed/fragmentSize;
+        head->allocated = quint32(blockInfo.elementCount);
         F(freePos).right = 0;
     }