Integer Overflow or Wraparound #1675

[ovidiu-benea]

Added check to determine if overflow/wrapping will occur

[mention-bot]

@ovidiu-benea, thanks for your PR! By analyzing the history of the files in this pull request, we identified @bagder, @yangtse and @linusnielsen to be potential reviewers.

[coveralls]

Coverage decreased (-75.3%) to 0.0% when pulling 9b4666a on ovidiu-benea:master into 798ad5d on curl:master.

[coveralls]

Coverage decreased (-75.3%) to 0.0% when pulling d976580 on ovidiu-benea:master into 798ad5d on curl:master.

[coveralls]

Coverage decreased (-0.03%) to 75.28% when pulling 0c12574 on ovidiu-benea:master into 798ad5d on curl:master.

[bagder]

I'm concerned about a few things with this patch:

1. I fear SIZE_MAX is not going to be universally available unless you make sure the dedicated header for it is included, and I suspect that it might be troublesome on legacy unixes. Just a suspicion. This can probably be addressed by an #ifdef that skips the test if the symbol doesn't exist.
2. Modern architectures have size_t as 64 bits and sockets are ints, 32 bits. An application thus can only keep a theoretical limit of 4 billion sockets (probably just 2 billion if we stick to positive integers). That's then not enough for this wrap-around to occur. So this check is not likely to ever trigger within a foreseeable future. What's the purpose of it again? A system with 32bit size_t still needs 2^29 allocated sockets, which is 500 million. Not likely to happen either.
3. I would like to verify this check with a unit test, which according to 2 has to be a broken application since it can't actually allocate that many sockets.

I propose we instead solve this issue with a comment in the source code!

[ovidiu-benea]

Hi,
Thanks for looking into this. I understand that this is not likely to happen. If an #ifdef that skips the test if SIZE_MAX doesn't exist is not a suitable fix, then we can add a comment.