Return a value from a thread

Challenge

A thread function returns a void*; pthread_join's second argument captures it. Carrying a small integer through that pointer (cast via intptr_t) is a common LP64-safe idiom.

Task

Implement long square_in_thread(long v) that runs a thread returning v*v through its return value, retrieves it with pthread_join, and returns it.

Input

• v: the value to square.

Output

v * v.

Example

square_in_thread(5)    ->   25
square_in_thread(0)    ->   0
square_in_thread(12)   ->   144

Rules

• Return (void*)(intptr_t)(v*v) from the thread.
• Capture it with pthread_join's second argument.

Input format

v: the value to square.

Output format

v * v.

Constraints

Return the result via the thread return value; capture it with join.

Starter code

#include <pthread.h>

long square_in_thread(long v) {
    /* TODO */
    return 0;
}