Re: [jgunthorpe:iommu_pt_vtd 8/34] ERROR: modpost: "__udivdi3" [drivers/iommu/generic_pt/fmt/iommu_amdv1.ko] undefined!

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Sep 16, 2025 at 07:20:43PM -0700, Nathan Chancellor wrote:
> as the bad commit, which certainly makes sense, as C23 made this GCC
> extension as part of the standard so clang needed to account for that.
> As far as I can tell, GCC did the same thing in
> 
>   https://gcc.gnu.org/cgit/gcc/commit/?id=3b3083a598ca3f4b6203284e01ed39ab6ff0844f
> 
>   "The standard feature gives all the values of such an enum the enumerated
>   type (while keeping type int if that can represent all values of the
>   enumeration), where previously GCC only gave those values outside the range
>   of int the enumerated type... this patch makes the change to types of
>   enumerators unconditionally (if that causes problems in practice we could
>   always make it conditional on C2x mode instead)."

That makes sense, I did not know it had changed like that

But still, I'd expect the compiler to retain the original behavior
unless std23/gnu23 is specified given that it does change codegen and
causes errors.

Though that is even more perplexing if gcc has been working this way
since 13 why does it avoid the udiv..

Jason