[Bug tree-optimization/114872] [13/14/15 Regression] Miscompilation with -O2 after commit r13-8037

["jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114872

--- Comment #28 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Dmitrii Pasechnik from comment #26)
> We have megabytes of code calling libraries where setjmp/longjmp is used,
> in github.com/sagemath/sage/ (most of it in Cython).
> 
> It looks like a huge hassle to put volatiles there. 
> Looks like we would need ways to disable particular optimisations which lead
> to these sorts of errors:-(

You mean turn off all optimizations then?  -O0.
Even that doesn't guarantee it will work if some such variables are declared
with register keyword.

It isn't just POSIX which says this, e.g. C99 also says:
"All accessible objects have values, and all other components of the abstract
machine
have state, as of the time the longjmp function was called, except that the
values of
objects of automatic storage duration that are local to the function containing
the
invocation of the corresponding setjmp macro that do not have
volatile-qualified type
and have been changed between the setjmp invocation and longjmp call are
indeterminate."
C89 said pretty much the same.