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

Martin Doucha
2022-11-28T12:00:41Z

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>

--
Martin Doucha mdoucha@suse.cz
QA Engineer for Software Maintenance
SUSE LINUX, s.r.o.
CORSO IIa
Krizikova 148/34
186 00 Prague 8
Czech Republic