Re: [PATCH] Fixup gdb.python/py-value.exp for bare-metal aarch64-elf

[Luis Machado <lgustavo@codesourcery.com>]

On 10/07/2016 05:23 AM, Yao Qi wrote:
> On Thu, Oct 6, 2016 at 5:27 PM, Luis Machado <lgustavo@codesourcery.com> wrote:
>> I noticed that testing aarch64-elf gdb with a physical board
>> ran into issues with gdb.python/py-value.exp. Further investigation showed
>> that we were actually trying to dereference a NULL pointer (argv) when trying
>> to access argv[0].
>>
>> Being bare-metal, argv is not guaranteed to be there. So we need to make sure
>> argv is sane before accessing argv[0].
>>
>> After fixing that, i noticed we were assuming a value of 1 for argc, which is
>> also not true, as i see 0 in my tests.
>
> If I understand C standard
> http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf correctly,
> "argv" can't be NULL.
>
> 5.1.2.2.1 Program startup
> ...
>  The value of argc shall be nonnegative.
>  argv[argc] shall be a null pointer.
>
> The first one implies that argc can be zero, and the second one implies
> argv can't be NULL.  In this case, argc is zero, so argv[0] can be
> dereferenced.
>

Ah, that makes sense indeed. Let me check the startup code and i'll get 
back to this patch (that may not be needed then).

Thanks,
Luis