MinGW-w64 pthread_cleanup_pop() error - c++

Question

when compiling a C++ program which contains a "call" to the pthread_cleanup_pop(E) macro, the following error is thrown by g++:
error: second operand to the conditional operator is of type 'void', but the third operand is neither a throw-expression nor of type 'void'
Now, the apparent problem here is that the macro above expands to
(*pthread_getclean() = _pthread_cup.next, (E?_pthread_cup.func((pthread_once_t *)_pthread_cup.arg):0));} where the second expression is a call to a function returning void, but the third expression is simply 0.
Althoug I get the basic issue here, I really don't see why the warning occurs in this particular use, as the "result" of the condition is not assigned to anything.
For the record: I compiled the C++ program using MinGW-w64 3.3.0 (GCC 4.9.2) both with and without -std=c++98. In both cases, the error occurs. If I compile the same code as a C program (both with or without -std=c99), there is no error.
Does anyone know how I could get rid of that error in C++, other than by editing pthread.h?
Many thanks in advance!
EDIT: Here is some example code for reference:
#include <pthread.h>
static int cancelled = 0;
static void test_thread_cleanup(void *_arg){
cancelled = 1;
}
static void* test_thread(void *_arg){
pthread_cleanup_push(&test_thread_cleanup, NULL); // push cleanup handler on stack
while (1){ // never left unless cancelled via pthread_cancel() from main()
pthread_testcancel(); // just test for pthread_cancel() having been called
}
pthread_cleanup_pop(1); // pop cleanup handler from stack
return NULL; // actually never reached
}
int main(void){
pthread_t th;
pthread_create(&th, NULL, &test_thread, NULL);
pthread_cancel(th);
pthread_join(th, NULL);
return cancelled;
}