uint overflow

[jujing]

In /Server/StateMachine.cc, function StateMachine::shouldTakeSnapshot, line 599 (version: 1.1.0)
uint64_t curr = 0;
if (lastIncludedIndex > stats.last_snapshot_index())
curr = lastIncludedIndex - stats.last_snapshot_index();
uint64_t prev = curr - 1;

Subtract operation overflows on operands "curr" and "1UL", whose values are unsigned constants, 0 and 1, respectively.

[ongardie]

That logic around that log message is a bit odd and probably doesn't do the right thing in all cases. @jujing, do you want to contribute a small patch or pull request for this? I think anything that avoids the underflow would be an improvement.

[jujing]

I wish to do that. But in my working environment, there are some limitations to prohibit me to commit code to github. And I only have a pad at home. I should solve the problem first.
For this issue, I think a simple way to avoid the underflow is that change the type of variables curr, prev, logEntries from uint64_t to int64_t.

[ongardie]

Ah. And I'm waiting permission from legal to write code...