From: Paul Eggert <eggert@cs.ucla.edu>
To: martin rudalics <rudalics@gmx.at>,
Stefan Monnier <monnier@IRO.UMontreal.CA>,
emacs-devel@gnu.org
Subject: Re: [Emacs-diffs] emacs-26 9bf66c6: Don't run FOR_EACH_FRAME when there's no frame left (Bug#29961)
Date: Sat, 16 Dec 2017 16:50:48 -0800 [thread overview]
Message-ID: <9d0b9c22-d386-cd0a-3947-a44d58b1ee0e@cs.ucla.edu> (raw)
In-Reply-To: <5A34EA93.1050501@gmx.at>
martin rudalics wrote:
> > I recognized callers that either --enable-gcc-warnings complained
> > about (because code after the FOR_EACH_FRAME loop clearly had
> > undefined behavior unless the loop iterated at least once),
>
> Which ones were these?
The code with undefined behavior is in delete_frame, after its 3rd use of
FOR_EACH_FRAME. This loop head is of the form 'FOR_EACH_FRAME (tail, frame1)
...' and the code after the loop assumes that frame1 is initialized, an
assumption that is false if Vframe_list is nil.
> Neither next_frame nor prev_frame exhibit such behavior IMO.
That's right. However, commit 8720f601e715e5f1d41f7cf863a525a1cc1bc12c removed
these functions' assertions that frame-list is non-nil, so I thought it wise to
resurrect them.
> > and
> > callers where historically there was an eassert that checked the
> > assumption.
>
> How far did you go back in history?
To commit 8720f601e715e5f1d41f7cf863a525a1cc1bc12c, which is the commit that
inserted the (now-removed) assumption that frame-list is non-nil when
FOR_EACH_FRAME is first executed.
next prev parent reply other threads:[~2017-12-17 0:50 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20171215073120.7671.79446@vcs0.savannah.gnu.org>
[not found] ` <20171215073122.52703204D3@vcs0.savannah.gnu.org>
2017-12-15 16:23 ` [Emacs-diffs] emacs-26 9bf66c6: Don't run FOR_EACH_FRAME when there's no frame left (Bug#29961) Stefan Monnier
2017-12-15 17:13 ` Paul Eggert
2017-12-15 18:17 ` martin rudalics
2017-12-15 19:09 ` Paul Eggert
2017-12-16 9:42 ` martin rudalics
2017-12-17 0:50 ` Paul Eggert [this message]
2017-12-17 10:46 ` martin rudalics
2017-12-18 0:39 ` Paul Eggert
2017-12-18 7:26 ` martin rudalics
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