[Webkit-unassigned] [Bug 173407] WTF::StringImpl::copyChars segfaults when built with GCC 7

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=173407

--- Comment #4 from Konstantin Tokarev <annulen at yandex.ru> ---
(In reply to Yusuke Suzuki from comment #3)
> (In reply to Konstantin Tokarev from comment #1)
> > I've run JSC benchmarks on Linux with GCC 7.1, performance results were
> > neutral after change of copyChars to do just memcpy
> 
> I like to use memcpy if it does not hurt performance.

I've checked just one platform/compiler combination so far.

I guess that initially this code path might have been added because of deficiency in old version of memcpy in macOS' libc, or gcc 4.2.

Could you recommend any specific benchmark that is signficantly affected by performance of copyChars?

> 
> Just out of curiosity, I wonder if we can use bitwise_cast here instead of
> reinterpret_cast.
> 
> Maybe, JF knows much about strict-aliasing, type punning and memcpy.

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