https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124542
Nathaniel Shead <nshead at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
CC| |nshead at gcc dot gnu.org
Last reconfirmed| |2026-03-19
Status|UNCONFIRMED |NEW
--- Comment #6 from Nathaniel Shead <nshead at gcc dot gnu.org> ---
Confirmed. The issue in this specific case is that when building the decl for
__vec_bit_cast, allocate_struct_function calls aggregate_value_p which
eventually tries to warn about "AVX vector return without AVX enabled changes
the ABI".
The diagnostic machinery then tries to print a context of "In function
__vec_bit_cast<...>", which ends up calling dump_template_bindings which calls
tsubst on each template parameter. This causes us to attempt to instantiate an
alias specialisation, which requires constraint satisfaction, which eventually
ends up walking into a tree that hasn't been loaded yet, causing the recursive
load.
Intuitively, we should not be performing instantiations when emitting a
diagnostic, I would think, as this could similarly cause recursive diagnostics;
it just seems that modules has made this easier to trigger. But it's not clear
to me how to do this just yet.
I'll try to reduce the testcase at least.
