Date: Tue, 5 Aug 2014 13:09:43 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: PATCH: don't call cleanup handlers after a regular return from the thread start function On Tue, Aug 05, 2014 at 06:51:34PM +0200, Jens Gustedt wrote: > Don't call cleanup handlers after a regular return from the thread > start function > > The chained list of cleanup handler function uses list items that are > local to the respective function of a cleanup block. In case of a > return out of the middle of a cleanup block, using these list items > can lead to UB. > > POSIX lists three different cases in which a cleanup handler that is > established on the cleanup stack has to be executed. Regular return > from the thread start function is not among these cases. > > Linux manpages are more explicit and state: > > Clean-up handlers are not called if the thread terminates by > performing a return from the thread start function. > > This patch aligns musl to that behavior. Could you clarify why this patch is necessary? I think such a return is explicitly UB: "The effect of the use of return, break, continue, and goto to prematurely leave a code block described by a pair of pthread_cleanup_push() and pthread_cleanup_pop() functions calls is undefined." http://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_cleanup_pop.html I don't see why the thread start function should be treated as special here. Rich
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