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  1. Qt
  2. QTBUG-22942

Qt can crash after exporting a PDF file with QPrinter due to deleted QFontEngines remaining in the QFontCache

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Details

    • Bug
    • Resolution: Done
    • P2: Important
    • 4.8.7
    • 4.7.4, 4.8.0
    • None
    • Windows
    • 8960f7356796948b161159cff404a9ebd1624c5f

    Description

      Our application sometimes crashes when using cached fonts after exporting a PDF, because a font engine that is in the cache has been deleted. I tried to reproduce this in a smaller test case, but unfortunately couldn't - however we have a 100% reproducible case in our application.

      Exporting a PDF (or EPS) file with QPrinter uses a QFontSubset when embedding fonts. The destructor of this class deletes its QFontEngine if the reference count is zero, but it doesn't check the cache count. I think this is the problem - there's nothing stopping the font engine from being destroyed when it's still stored in the cache.

      The fix should be simple: just add a check for cache_count == 0 in the QFontSubset destructor, before the font engine is destroyed.

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          # Subject Branch Project Status CR V

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              ritt.ks Konstantin Ritt
              jlarcombe James Larcombe
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                Created:
                Updated:
                Resolved:

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