检查 pthread_cond_t 的值

Question

I am trying to check the value of a variable of type pthread_cond_t in a while loop condition.

The variable is defined in a node struct with the following form:

pthread_cond_t cv;

When I try to check the value of this using != or == NULL I get errors that this can't be done. Here is what it looks like when I try to check it:

while(!node->cv) {

where node is a pointer to a struct containing the cv.

I get the error "wrong argument type to unary exclamation mark, since I guess it's not a boolean. is there a way to check if this condition variable has value?

Answer 1

Condition variables don't have values. They're abstract objects you wait on and signal, and are abstractly associated with boolean-result expressions (predicates) involving other variables in your program that are protected by the associated mutex. So instead of:

while (!node->cv)

you do:

while (some_predicate(node))
    pthread_cond_wait(&node->cv, &node->mtx);

This has to be done with the mutex already locked.