[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization

jakub at gcc dot gnu.org gcc-bugzilla@gcc.gnu.org
Tue Jun 14 09:36:09 GMT 2022


--- Comment #12 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to John Kanapes from comment #11)
> (In reply to Richard Biener from comment #9)
> > Note that GCC 9 is no longer supported.  Note one common error resulting in
> > SIGILL is when you fall through to an unreachable place which could be
> > padding
> > (like when there's a missing return in a function).
> Hmmm.
> gcc 9.40 is the distro gcc for Ubuntu 20.04, which is LTS and still
> supported.

In this case it is Ubuntu that supports it, so you'd need to ask Ubuntu to fix
(if it is a compiler bug of course), because upstream GCC 9.5 was the last
release and there won't be any changes for the GCC 9 series.  If it reproduces
with a newer compiler, it can be fixed upstream in the still supported releases
and perhaps Ubuntu could backport it if you ask them to.

> Does this mean that no action will be taken upon resolving this ticket?

Depends on if it is reproducible with a supported compiler.

> I am trying to recreate this bug in a smaller, more concise context.
> It is not an obvious bug. This is valid code, and it takes a large chain of
> previous steps to get it wrong at runtime. It used to work with previous
> gccs, but it now seems broken:(

Claiming it is valid code until it is analyzed is premature.  It can very well
be undefined behavior in the code.

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