On Jun 11, 2008, at 1:22 PM, Brendan Gregg - Sun Microsystems wrote:
> G'Day,
>
> This issue was news to me, and may be useful for readers of this list.
>
> In brief:
>
> USDT providers on MacOS X that are built with the -dead_strip linker
> option
> have their probes fired twice by mistake. The workaround is not to
> use
> the -dead_strip option.
>
> Some more details:
>
> After integration of the JavaScript DTrace provider into Firefox, the
> Mozilla developers discovered that probes were firing twice by
> mistake -
> so results such as @[probename]=count() were doubled.
>
> The most likely reason was that probe placement had become incorrect -
> during provider development the Firefox code was changing, and I had
> to
> tweak the probe locations a few times. It sounded like more of the
> same,
> but I couldn't see why this was happening in the code.
>
> The Mozilla developers discovered it happened with the -dead_strip
> linker
> option!:
>
> https://bugzilla.mozilla.org/show_bug.cgi?id=403132
>
> which from a quick search looks like it is a known issue:
>
>
> http://www.opensource.apple.com/darwinsource/10.5/ld64-77/unit-tests/test-cases/dtrace-static-probes/Makefile
>
> as -dead_strip is part of the Apple sanity checks.
>
> That's all I know. If you know more details, please reply. :-) I
> also
> don't know if this was fixed in the recent release of MacOS X (if it
> is
> even considered a bug?).
Brendan,
This is <rdar://problem/5628149>.
OS X 10.5.3 does not have the fix, but if you download the free
iPhone SDK, it has a
patched linker which fixes this issue.
James M
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