Re: [PATCH][RFC] Extend "memparse" to allow a NULL return pointer value.

[Oleg Verych <olecom@flower.upol.cz>]

* Sat, 15 Sep 2007 12:27:07 -0400 (EDT)

> Extend the memparse() routine to allow a caller to use NULL as the
> second parameter value if he has no interest in that returned value.

(not `he', but `it', even if `he', then better `callers' + `they')

> ---
>
>   there appear to be quite a number of calls to "memparse" which have
> no use for the value returned in the second parameter (the current
> pointer after the successful parse), but which are still forced to
> supply a valid char** address since they have no choice but to accept
> that value coming back.  in many cases, that value is accepted just
> before the end of the calling function, making it clear that the value
> is ignored entirely, anyway.

A posteriori value, stored in this pointer serves very important role: it
validates returned result. Caller must do this. But if programmer doesn't
know problems (see below), `must' melts down to `may'.

If you take a look at simple_strtoull(), it already doesn't care if this
pointer is NULL or not. (So patch is NULL :)

But take closer look. If it returns `0' (zero), it is not clear if this
zero was parsed or not, unless you can compare `ptr' and `retptr'.
Another case if entire string have no valid number to parse (see
strtol(3)).

This is problem of this particular function, that is copied form
ordinary C. For instance see <http://bugs.debian.org/431320>.
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