https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116481
Richard Sandiford <rsandifo at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |rsandifo at gcc dot gnu.org
--- Comment #9 from Richard Sandiford <rsandifo at gcc dot gnu.org> ---
(In reply to Bruno Haible from comment #7)
> Thanks for the attempted advice. But, no, converting a pointer to uintptr_t
> and later back to a pointer is bad for portability: It does not work on the
> CHERI architecture and its implementation on the ARM Morello chip
> https://developer.arm.com/Architectures/Morello, because it loses the tag
> bits that are essential for accessing the pointer. See
> https://www.gnu.org/software/gnulib/manual/html_node/C99-features-avoided.
> html and https://lists.gnu.org/archive/html/bug-gnulib/2023-12/msg00021.html
> .
I think Richard's point still stands though. Conversion to and from
(u)intptr_t does not in itself drop the tag bit. CHERI/Morello (u)intptr_t can
hold exactly what a void* can hold. If the tag bit is dropped by going out of
bounds, that's a feature, not a bug, and would happen equally for void*/char*
arithmetic as for (u)intptr_t arithmetic.
