[Webkit-unassigned] [Bug 150235] New: SameSizeAs* structs wrongly assume sizeof(ptr)==sizeof(std::unique_ptr)

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=150235

            Bug ID: 150235
           Summary: SameSizeAs* structs wrongly assume
                    sizeof(ptr)==sizeof(std::unique_ptr)
    Classification: Unclassified
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebCore Misc.
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: rupsharma at ea.com

Hi,

In regard to all the static assertions, to check the sizes of the data-structures using SameSizeAs* structs, it is wrongly assumed, that sizeof (std::unique_ptr) is same as sizeof (pointer) for all compilers. 
Therefore, I would suggest to list them separately while computing the sizes.

To give an example:
In WebCore\dom\ElementRareData.cpp

The structure should look like:
struct SameSizeAsElementRareData : NodeRareData {
    short indices[2];
    unsigned bitfields;
    RegionOversetState regionOversetState;
    LayoutSize sizeForResizing;
    IntSize scrollOffset;

// CHANGE BEGINS HERE . Earlier it was :void* pointers[7];
    void* pointers[4];
    std::unique_ptr<DatasetDOMStringMap> pointer2;
    std::unique_ptr<ClassList> pointer3;
    std::unique_ptr<NamedNodeMap> pointer4;
// CHANGE ENDS HERE
};

Making the above change,  works perfectly for us without throwing any compile-time assert at:
static_assert(sizeof(ElementRareData) == sizeof(SameSizeAsElementRareData), "ElementRareData should stay small");

Thanks,
Rupali

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