GCC atomic memory access built-in functions (IBM extension)

This section provides reference information for atomic memory access built-in functions whose behavior corresponds to that provided by GNU Compiler Collection (GCC). In a program with multiple threads, you can use these functions to atomically and safely modify data in one thread without interference from other threads.

These built-in functions manipulate data atomically, regardless of how many processors are installed in the host machine.

In the prototype of each function, the parameter types T, U, and V can be of pointer or integral type. U and V can also be of real floating-point type, but only when T is of integral type. The following tables list the integral and floating-point types that are supported by these built-in functions.

Table 1. Supported integral data types

signed char	unsigned char
short int	unsigned short int
int	unsigned int
long int	unsigned long int
long long int	unsigned long long int
bool	_Bool

In the prototype of each function, the ellipsis (...) represents an optional list of parameters. XL C/C++ ignores these optional parameters and protects all globally accessible variables.

The GCC atomic memory access built-in functions are grouped into the following categories.