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From: Eli Zaretskii <eliz@gnu.org>
Newsgroups: gmane.emacs.devel
Subject: Re: (select-window nil) crash with gcc-8.2.0
Date: Sun, 07 Apr 2019 21:38:07 +0300
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To: Paul Eggert <eggert@cs.ucla.edu>
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> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Sun, 7 Apr 2019 11:33:22 -0700
> Cc: emacs-devel@gnu.org
> 
> and that last movq dereferences the window pointer in %rbx before the result of 
> WINDOWP is checked to verify that the argument (originally in %rdi, now in %rbx) 
> is indeed a window.
> 
> Could you file a GCC bug report for this? And in the meantime, I wouldn't use -Os.

Thanks.  So just -O2 produces correct code?  Because I think GCC 8 is
quite popular, and the default build uses -O2.  If -O2 is prone to
something similar, maybe we should make some changes in the code to
avoid that.