std::condition_variable checks the condition for the first time, or do you have to wait for someone to make a notify?

问题

std::condition_variable checks the condition for the first time, or do you have to wait for someone to make a notify?

回答1:

This is answered by reading documentation.

It's like:

while (!pred()) {
    wait(lock);
}

So, the condition is checked first.

This can also be shown by testing it (though, to be fair, it's hard to know just from that whether the results are deterministic).

来源：https://stackoverflow.com/questions/61107175/stdcondition-variable-checks-the-condition-for-the-first-time-or-do-you-have