Re: [PATCH] [sim] Fix build failure in d10v sim

[Mike Frysinger via Gdb-patches <gdb-patches@sourceware.org>]

On 10 May 2021 16:14, Luis Machado via Gdb-patches wrote:
> While building all targets on Ubuntu 20.04/aarch64, I ran into the following
> build error:
> 
> In file included from /usr/include/string.h:495,
>                  from ../../bfd/bfd.h:48,
>                  from ../../../../repos/binutils-gdb/sim/d10v/interp.c:4:
> In function 'memset',
>     inlined from 'sim_create_inferior' at ../../../../repos/binutils-gdb/sim/d10v/interp.c:1146:3:
> /usr/include/aarch64-linux-gnu/bits/string_fortified.h:71:10: error: ‘__builtin_memset’ offset [33, 616] from the object at ‘State’ is out of the bounds of referenced subobject ‘regs’ with type ‘reg_t[16]’ {aka ‘short unsigned int[16]’} at offset 0 [-Werror=array-bounds]
>    71 |   return __builtin___memset_chk (__dest, __ch, __len, __bos0 (__dest));
>       |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> make[3]: *** [Makefile:558: interp.o] Error 1
> 
> I looked at a different sim (cr16), and it zeroes out the entire State, not
> just the registers.

it's clearing more than just the regs.  it's clearing all the members in the
state struct from regs up to mem.  so regs, cregs, sp, a, slot, etc...  if
you want to change it, the comment in the header probably needs adjusting.

> It is unclear why we have the casts to uintptr.

because pointer math on diff types isn't allowed, and the 3rd arg to memset
needs to be a scalar integer.  so casting to uintptr_t is the correct way to
calculate this value.

> The following patch fixes this for me.
> 
> -  memset (&State.regs, 0, (uintptr_t)&State.mem - (uintptr_t)&State.regs);
> +  memset (&State, 0, sizeof (State));

i think changing the first arg to &State is sufficient and keeping the mem-regs
calculation.  and maybe add a static assert that &State == &State.regs ?

this code needs to be rewritten fundamentally at some point :/.
-mike