[Webkit-unassigned] [Bug 102828] r134080 causes heap problem on linux systems where PAGESIZE != 4096

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=102828


Mark Hahnenberg <mhahnenberg at apple.com> changed:

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--- Comment #32 from Mark Hahnenberg <mhahnenberg at apple.com>  2013-01-18 10:21:28 PST ---
(From update of attachment 183468)
View in context: https://bugs.webkit.org/attachment.cgi?id=183468&action=review

Additionally, there's a function named "sizeFromCapacity" in MarkStackSegment. That doesn't appear to be called from anywhere, so let's remove it while we're here.

> Source/JavaScriptCore/heap/MarkStack.cpp:47
> +#if COMPILER(CLANG)

Let's not ignore the warnings.

> Source/JavaScriptCore/heap/MarkStack.cpp:52
> +const size_t MarkStackArray::s_segmentCapacity = MarkStackSegment::capacityFromSize(MarkStackSegment::blockSize);

If we could use C++11, we could just add constexpr to capacityFromSize and call it a day. Unfortunately we can't, so we have to use some template magic.

Instead of using the old capacityFromSize static function, let's rework the code a little bit. From some brief grepping, it appears that this is the only client of the capacityFromSize function. So in order to get a compile-time constant value, we can instead use a template. Something along the lines of:

template <size_t size> struct CapacityFromSize {
    static const size_t value = // body of current capacityFromSize
};

Stick that somewhere private in MarkStackArray and grab the ::value when defining s_segmentCapacity.

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