CODEWITHSUNDEEP
c
ikh
ikh

Reputation: 10417

strtoXX : check overflow

As we know, strtoXX functions return max(or min) value if overflow occur, for example, strtoul("999999999999999999999999999999999", NULL, 0) returns ULONG_MAX. But strtoul("0xffffffff", NULL, 0) returns also ULONG_MAX(if sizeof(unsigned long) == 4).

Then, how can I check overflow?

Upvotes: 1

Views: 92

Answers (1)

Marco A.
Marco A.

Reputation: 43662

http://www.cplusplus.com/reference/cstdlib/strtoul/

If the value read is out of the range of representable values by an unsigned long int, the function returns ULONG_MAX (defined in ), and errno is set to ERANGE.

You're dealing with unsigned integers, so it doesn't matter what sign your integer has: they're all treated as unsigned integers. And 0xFF FF FF FF (assuming 4 bytes as you're doing) is negative, but it's being treated as +4294967295 (not 2's complement). And that's also exactly the value of ULONG_MAX in that case.

Upvotes: 4

Related Questions