Re: Finding a word inside a string
- From: Barry Schwarz <schwarzb@xxxxxxxx>
- Date: Fri, 24 Sep 2010 20:49:58 -0700
On Fri, 24 Sep 2010 19:09:23 -0700 (PDT), Chad <cdalten@xxxxxxxxx>
wrote:
if(value_str[0])
{
v = strtol(value_str, (char**) NULL, 10);
What purpose do you think the cast serves? What would be different if
you deleted it?
if(0 == v && ERANGE == errno) return ERR_CONVERSION_CHAR_TO_INT;
}
So -10 will never be valid input to your code?
If strtol sets errno to ERANGE, you have already invoked undefined
behavior in the previous assignment to v (unless INT_MAX happens to
equal LONG_MAX). Regardless, when errno is set to ERANGE, v will
never be zero so the if can never evaluate to true.
If v happens to be zero, you do not know whether that is because your
text evaluated to 0 or because strtol could not perform any
conversion. Using NULL as the second argument to strtol eliminated
your best hope of doing error analysis.
Would a better method be something like the following
errno = 0;
if (v == 0) {
if (errno == ERANGE) {
return errno;
}
return ERR_CONVERSION_CHAR_TO_INT;
}
How could it be? If v is zero, the errno cannot be ERANGE. It makes
no sense to test a condition when the answer is already known.
On the other hand, if errno is ERANGE then the code invokes undefined
behavior.
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- References:
- Finding a word inside a string
- From: arnuld
- Re: Finding a word inside a string
- From: Barry Schwarz
- Re: Finding a word inside a string
- From: Chad
- Finding a word inside a string
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