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From: Rich Felker <dalias@libc.org>
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Subject: Re: Duplicate call to pthread_join segvs
Date: Thu, 18 Aug 2016 08:47:49 -0400
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On Thu, Aug 18, 2016 at 12:51:23PM +0100, Steve Osselton wrote:
> Hi,
> 
> Am using musl on the latest Alpine Linux release. Although the behaviour of
> calling pthread_join on
> the same thread is undefined, would be nice if returned an errno as opposed
> to a segv:

No, that would be harmful because it would hide an extremely serious
bug (think what happens if another thread had been created after the
first join and its id happened to match the id of the already-joined
one). It would also be generally impossible to produce. pthread_join
is inherently a free-type operation (it frees a resource) and
double-frees are not reliably detectable unless the implementation
just never reuses freed resources at all (i.e. leak them).

Rich