Re: [PATCH] Workaround poitner arithmetic bug of mescc for 64-bit arches.

[Andrius Štikonas]

Hi,

Perhaps you can reword this a bit more. Ekaitz and I looked at this a bit more 
and in fact this is a proper fix and not a workaround.

Fix va_start macro to work for 64-bit arches.
        
* include/stdarg.h: Fix va_start to point to correct location.


the problem was that &last + 1 was adding sizeof the type to address of last 
but weed size of register
mescc pushes int arguments on stack like this on 64-bit arch:
arg1( 4 bytes), 4 bytes of zeros, arg2 (4 bytes), 4 bytes of zeroes, ...
so the gaps between arguments are register sized (due to push operation).

But on 32-bit arch it was arg1 (4 bytes), arg2 (4 bytes), etc, so it just 
happened to work by accident
because sizeof(int) was equal to sizeof(register).

Hence, my commit is not really a workaround around mescc bug but a proper fix 
for a macro.

Andrius

2023 m. spalio 25 d., trečiadienis 07:38:49 BST Janneke Nieuwenhuizen rašė:
> Andrius tikonas writes:
> 
> > &last + 1 was adding just 4 to address on riscv64.
> >
> > * include/stdarg.h: Fix va_start to point to correct location.
> 
> Nitpickly changed to
> 
>     * include/stdarg.h (va_start): Fix to point to correct location.
> 
> and applied to wip-riscv.
> 
> Thanks!
> Janneke
> 
>