[Bug c++/105297] [12 Regression] new modules 'xtreme' test cases FAILs

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105297

Jiu Fu Guo <guojiufu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |guojiufu at gcc dot gnu.org

--- Comment #11 from Jiu Fu Guo <guojiufu at gcc dot gnu.org> ---
(In reply to Patrick Palka from comment #10)
> 
> Interestingly that doesn't seem to make a difference.  What seems to matter
> is whether the constexpr function modifies the CONSTRUCTOR that it returns:
> 
> constexpr auto foo() {
>   struct S { int d; } t = {};
>   t.d = 0; // doesn't ICE if this line is commented out
>   return t;
> }
> 
> template<int>
> int bar() {
>   constexpr auto t = foo();
>   return 0;
> }

Right, it is weird. Some PRs on Xtreme-* failure (including ICE) were also
reported before. e.g. PR100052, PR101853, PR99910.  As commented in those PRs,
these may be random failures, and changes in headers that could expose the ICE.
I'm also wondering if this may be an issue hidden inside somewhere (GC?).