[libcxx] r215740 - Revert "Turn off extern templates for most uses."

[Eric Fiselier]

> Just as a small data point, with an instrumented program and
uninstrumented libc++ I see 575 msan failures without extern templates,
and 724 with. If libc++ is instrumented, it's more like 200 (and many of
these look like they're just because I've messed up using the
instrumented library with the instrumented executable).

A large amount of the test failures w/ MSAN are because some tests replace
operator new and operator delete. This causes a linking error.
I don't have specific numbers for the amount of tests that do this but you
should take that into consideration.




On Sun, Aug 17, 2014 at 7:15 PM, Howard Hinnant <howard.hinnant at gmail.com>
wrote:

> On Aug 17, 2014, at 9:06 PM, Justin Bogner <mail at justinbogner.com> wrote:
>
> > I really don't think it's worth the cost of insantiating these very
> > fundamental templates in *every single user* to work around a limitation
> > in the memory sanitizer. This is an unreasonable amount of overhead for
> > standard library types.
>
> Always measure.  I’m not saying you’re wrong.  I’m saying you’re stating a
> performance conclusion without measurements (which should never be
> acceptable).
>
> Howard
>
>
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