Re: [RFC v1 2/2] Makeconfig: Compile glibc with -fno-delete-null-pointer-checks

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

On 2023-07-11 09:41, Florian Weimer via Libc-alpha wrote:
> * Alejandro Colomar via Libc-alpha:
> 
>> Don't undefine __nonnull to prevent compiler optimizations.  Instead,
>> tell the compiler to not optimize based on the attribute, via the
>> appropriate flag.
> 
> The manual for GCC 13 says:
> 
>       For function definitions:
>          • If the compiler determines that a function parameter that is
>            marked with nonnull is compared with null, and
>            ‘-Wnonnull-compare’ option is enabled, a warning is issued.
>            *Note Warning Options::.
>          • The compiler may also perform optimizations based on the
>            knowledge that ‘nonnull’ parameters cannot be null.  This can
>            currently not be disabled other than by removing the nonnull
>            attribute.
> 
> So this isn't actually equivalent today, and I think it impacts our
> ability to deal with null pointer errors in the implementation (in
> function definitions).

+1, this situation is equivalent to why we remove the access attribute 
during fortification too; it hinders the ability of the implementation 
to do those checks at runtime.

Thanks,
Sid