Re: [PATCH] Catch under/overflow cases in cvtnum() and cvttime().

[Eric Sandeen <sandeen@sandeen.net>]

On 7/12/14, 1:13 AM, Arkadiusz Miśkiewicz wrote:
> On Saturday 12 of July 2014, Eric Sandeen wrote:
>> On 7/11/14, 2:34 PM, Arkadiusz Miśkiewicz wrote:
>>> cvtnum() and cvttime() silently ignore overflows. This leads to error
>>> conditions not being catched. Example:
>>>
>>> $ xfs_quota -x -c 'limit -u bsoft=987654321098765432199 \
>>>
>>>         bhard=987654321098765432199 999' /
>>>
>>> $
>>>
>>> Fixed version:
>>> $ xfs_quota -x -c 'limit -u bsoft=987654321098765432199 \
>>>
>>>         bhard=987654321098765432199 999' /
>>>
>>> xfs_quota: Error: could not parse size 987654321098765432199.
>>> xfs_quota: unrecognised argument bsoft=987654321098765432199
>>
>> So, strtol(3) suggests setting errno to 0 before the call:
>>
>> NOTES
>>        Since  strtol()  can  legitimately  return  0,  LONG_MAX,  or 
>> LONG_MIN (LLONG_MAX or LLONG_MIN for strtoll()) on both success and
>> failure, the calling  program should set errno to 0 before the call, and
>> then deter- mine if an error occurred by checking  whether  errno  has  a 
>> non-zero value after the call.
>>
>> Ditto for strtoul().
> 
> Hm, my man pages 3.70 don't have such notes, strtol(3):
> 
> NOTES
>        In locales other than the "C" locale, also other strings may be 
> accepted.  (For example, the thousands separator of the current locale may be 
> supported.)
> 
>        BSD also has
> 
>            quad_t
>            strtoq(const char *nptr, char **endptr, int base);
> 
>        with completely analogous definition.  Depending on the wordsize of the 
> current architecture, this may be equivalent to strtoll() or to strtol().
> 
>>
>> I guess that is just to ensure that there's not a leftover errno
>> when we make the call?  Worth doing, maybe?
> 
> ERANGE is checked in few other places already in input.c and none initialize 
> errno before strtoul() call.

http://c-faq.com/misc/errno.html suggests it too:

> It's only necessary to detect errors with errno when a function does
> not have a unique, unambiguous, out-of-band error return (i.e.
> because all of its possible return values are valid; one example is
> atoi). In these cases (and in these cases only; check the
> documentation to be sure whether a function allows this), you can
> detect errors by setting errno to 0, calling the function, then
> testing errno.

I wonder why it was removed from the man page, it makes sense to me, but
maybe I'm missing something.

-Eric

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