[Webkit-unassigned] [Bug 26453] New: Null Cairo context will crash Windows Cairo Build

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=26453

           Summary: Null Cairo context will crash Windows Cairo Build
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: PC
        OS/Version: Windows XP
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebKit Misc.
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: bfulgham at webkit.org


The DRT test suite identified a crash bug in the Windows Cairo build.

If a null platform graphics context is passed to the GraphicsContext
constructor, e.g., from Line 3724 in RenderBlock.cpp:

        GraphicsContext context((PlatformGraphicsContext*)0);

The internal Windows Cairo sync function (which attempts to keep the Windows DC
in sync with the Cairo one) will crash when it attempts to retrieve the Cairo
surface from the null pointer (see Line 180 in GraphicsContextCairoWin.cpp):

    cairo_surface_t* surface = cairo_get_target(cr);

The fix is to check for a null pointer before attempting to do so.


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