__sync_bool_compare_and_swap

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Note: When you invoke the Clang-based front end of IBM® XL C/C++ for AIX® 16.1 using the xlclang or xlclang++ invocation command, GCC compare and swap built-in functions are not supported. Use the C++11 atomics features instead.

Purpose

This function compares the value of __compVal with the value of the variable that __p points to. If they are equal, the value of __exchVal is stored in the address that is specified by __p; otherwise, no operation is performed.

A full memory barrier is created when this function is invoked.

Prototype

bool __sync_bool_compare_and_swap (T* __p, U __compVal, V __exchVal, ...);

Parameters

__p: The pointer to a variable whose value is to be compared with.
__compVal: The value to be compared with the value of the variable that __p points to.
__exchVal: The value to be stored in the address that __p points to.

Return value

If the value of __compVal and the value of the variable that __p points to are equal, the function returns true; otherwise, it returns false.