Re: strtonum(3) from OpenBSD?
der Mouse <mouse <at> Rodents-Montreal.ORG>
2009-07-01 19:28:41 GMT
>> [...], but it does matter which test is done first if errno might
>> contain a trap representation.
> I meant in the strict ordering of terms in the test expression(s).
> if (errno == ERANGE && rval == LONG_MAX)
> if (rval == LONG_MAX && errno == ERANGE)
These are not equivalent if errno might contain a trap representation
for non-LONG_MAX returns. (Because of strtol()'s special case for
errno, this can happen only if it was that way on entry.)
>> [...] if strtol were allowed to leave trash in errno, [...]
> Hmmm... yes, but _only_ if that "trash" value were ERANGE (or the
> undocumented EINVAL return).
Yes...so? Trash has a nasty habit of being what you least want it to
at the most inconvenient times.
> If I understand you correctly, you are suggesting that ERANGE may be
> inadvertently set by some arithmetic operation during the conversion
> of a string that represents _exactly_ LONG_MAX.
Not necessarily _arithmetic_ operation. There is no guarantee that
strtol() and friends are leaf routines, and, indeed, it's not
implausible that they may do something (like locale setup) which may
leave relatively unpredictable trash in errno.
But, since there is no other way to disambiguate LONG_MAX, strtol()'s
interface contract includes special mention of errno - namely, that a
(Continue reading)
> > In all cases, not just strtol, both conditions must hold, but it does > matter which test is done first if errno might contain a trap > representation. I meant in the strict ordering of terms in the test expression(s). I.e. all of the following statements are equivalent. I.e. it does not matter which test is done first. It can be either errno first: if (errno == ERANGE && rval == LONG_MAX) err(); if (errno == ERANGE) if (rval == LONG_MAX) err(); etc., or the return value first: if (rval == LONG_MAX && errno == ERANGE) err();
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