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From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/101830] [12 Regression] Incorrect error
 messages beginning with r12-2591 (backward jump threader)
Date: Thu, 12 Aug 2021 20:15:32 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101830

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|INVALID                     |FIXED

--- Comment #12 from Martin Sebor <msebor at gcc dot gnu.org> ---
No problem.

By the way, it looks to me like safe_inc_pos() also isn't entirely safe sin=
ce
testing the result of the postincrement lets pos reach 1024 on function ret=
urn.
 It should either use preincrement or 1023 as the bound.

It's of course possible to issue a more nuanced warning ("may be out of
bounds") for expressions that are invalid only under some condition, in bas=
ic
blocks that aren't dominated by function entry.  It has been suggested (and
considered) a number of times before.  The problem with a simplistic soluti=
on
like that is that it would result in the vast majority of warnings being
phrased this way, because most are in such blocks.  The only certain warnin=
gs
would be either in trivial functions or in the initial basic blocks.  I'm
working on introducing this distinction for PHIs but I don't have any ideas
what to do for problems like this one.=