Messages in this thread | | | From | Rasmus Villemoes <> | Subject | Re: [PATCH 01/10] Add parse_integer() (replacement for simple_strto*()) | Date | Mon, 04 May 2015 23:48:27 +0200 |
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On Mon, May 04 2015, Alexey Dobriyan <adobriyan@gmail.com> wrote:
>> There are lots of callers of memparse(), and I don't think any of them >> are prepared to handle *endp ending up pointing before the passed-in >> string (-EINVAL == -22, -ERANGE == -34). I can easily see how that could >> lead to an infinite loop, maybe worse. > > Yeah, possible bug could become worse, I'll add error checking, > but, seriously, you're defending this :^) > > case Opt_nr_inodes: > ===> /* memparse() will accept a K/M/G without a digit */ > ===> if (!isdigit(*args[0].from)) > ===> goto bad_val; > pconfig->nr_inodes = memparse(args[0].from, &rest); > break; >
No, I'm not defending memparse(), simple_strto* or any of their callers. I'm just trying to say that you can't change the semantics of memparse() without considering all its callers.
I don't think there's any way to "add error checking" and preserve the exact memparse() semantic - in other words, I don't think simple_strto* can actually be implemented in terms of parse_integer. But that's not a bad thing - we want to get rid of those.
> memparse() is misdesigned in the same sense strtoul() is misdesigned. > Every "memparse(s, NULL)" user is a bug for example.
Yes, memparse is misdesigned, since it doesn't have a way to indicate error. That leads me to: There's no point in adding error checking to the integer parsing part without also checking the left shifts for overflow.
I think the right approach is to rename memparse to legacy_memparse and introduce a memparse with semantics that allow error checking. One could start by introducing that under the name sane_memparse. But there are probably lots of simple_strto*() uses that are easier to eliminate.
Rasmus
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