Re: [LTP] [PATCH v1] execl(), execlp() and execle() require proper termination of argument list

Richard Palethorpe
2022-12-05T09:28:06Z

Hello,

Richard Palethorpe <rpalethorpe@suse.de> writes:

> Hello,
>
> Martin Doucha <mdoucha@suse.cz> writes:
>
>> On 28. 11. 22 12:11, Petr Vorel wrote:
>>> Hi Michael,
>>> sorry to bother you, could you please comment our discussion about
>>> execl{,e,p}()
>>> termination of argument list being NULL vs. (char *)NULL vs. (void*)0?
>>> Martin reported [2] that man page suggests (char*)NULL, his view of
>>> reason [3]:
>>> NULL may be defined as simple integer 0. When int is 32bit and pointers
>>> 64bit, this will cause trouble in variadic functions such as execlp().
>>> Cyril pointed out [4]: NULL is required to be 0 cast to void* in
>>> POSIX. [5]
>>> Therefore what should be really used?
>>> Kind regards,
>>> Petr
>>> [2]
>>> https://lore.kernel.org/ltp/8587b908-a035-a96a-7233-2863b7bc30ca@suse.cz/
>>> [3] https://lore.kernel.org/ltp/af63ed9a-7108-fd19-fe2c-4b56be85d068@suse.cz/
>>> [4] https://lore.kernel.org/ltp/Y4DSmk7uY9zUUQsV@yuki/
>>> [5] https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stddef.h.html
>>
>> Cyril is correct that we don't need this fix as long as we use C99 or
>> later with POSIX-compliant build system. The explicit type cast is
>> required only in C++ where there's no explicit conversion from void*
>> to other pointer types and therefore NULL must be defined as integer
>> instead of void* pointer constant.
>>
>> Then again, pedantically following the docs won't break anything either.
>>
>> Acked-by: Martin Doucha <mdoucha@suse.cz>
>
> I think the docs are wrong here, they should probably specify where it
> is needed to cast to (char *). We are (now) using a superset of c99 so
> we are not effected.
>
> The issue I see is that this is yet another thing to remember to enforce
> and for no apparent benefit. OTOH if there is some compiler/analyser
> flag which creates a warning then I would not be against adding that.

Setting this to Not Applicable in patchwork. This is not final, but it
will remove it from the queue.

>
> --
> Thank you,
> Richard.

--
Thank you,
Richard.