Re: [PATCH v1] xstrtol: Remove dead code

[Alejandro Colomar]

On Thu, Jul 18, 2024 at 11:09:40PM GMT, Bruno Haible wrote:
> Hi Alejandro,

Hi Bruno,

> > strtol(3) has a limited set of possible states:
> > ...
> > The condition '*endp != s && errno != 0 && errno != ERANGE' is
> > unreachable.  The only errno possible if '*endp != s' is ERANGE.
> 
> Such a statement can be true if you look at the standards (ISO C, POSIX).
> 
> However, there's a difference between what the standards say and what the
> systems actually do. The Gnulib documentation contains thousands of examples
> of such differences.
> 
> Gnulib therefore (almost) never assumes that there are no possible errno
> values besides the ones listed in the standards.
>   - Some systems return "wrong" errno values. Example: [1]
>   - Some systems fail with ENOMEM when memory is tight. Who says that
>     an implementation of strtol() cannot use malloc() ? Some implementations
>     of strtod() do use malloc().
> 
> So, what you call "dead code", I call "defensive programming". I would not
> like to apply this patch.

Makes sense.  I think we should document that possibility in the manual
page.  Maybe say that other errno values are possible in some systems?
Otherwise, it's already a hell of a function to take care of, and most
uses don't handle that possibility at the moment.  (Yet more reasons to
use a wrapper that returns -1 & sets errno on error, as the rest of
libc.)

Would you send a patch?  (I'd write it myself, but you probably can
provide more info in the commit message.)

Have a lovely night!
Alex

> 
> Bruno
> 
> [1] https://www.gnu.org/software/gnulib/manual/html_node/getlogin_005fr.html
> 
> 
> 

-- 
<https://www.alejandro-colomar.es/>

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