[Webkit-unassigned] [Bug 74646] New: RenderObject is bigger on Windows

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=74646

           Summary: RenderObject is bigger on Windows
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: rniwa at webkit.org
                CC: hyatt at apple.com, darin at apple.com, mitz at webkit.org,
                    koivisto at iki.fi, aroben at apple.com, tony at chromium.org,
                    ojan at chromium.org


Unlike gcc and clang, MSVC pads each consecutive member variables of the same type
in bitfields. e.g. if you have:
sturct AB {
unsigned m_1 : 31;
bool m_2 : 1;
}
then MSVC pads m_1 and allocates sizeof(unsigned) * 2 for AB whereas gcc and clang
only allocate sizeof(unsigned) * 1 for AB.

As a result, RenderObject consumes 44 bytes instead of 32 bytes when compiled on Windows by cl.exe.

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