GLibonce

#define g_once (
once,
func,
arg
)

The first call to this routine by a process with a given GOnce struct calls func with the given argument. Thereafter, subsequent calls to g_once() with the same GOnce struct do not call func again, but return the stored result of the first call. On return from g_once(), the status of once will be G_ONCE_STATUS_READY.

For example, a mutex or a thread-specific data key must be created exactly once. In a threaded environment, calling g_once() ensures that the initialization is serialized across multiple threads.

Calling g_once() recursively on the same GOnce struct in func will lead to a deadlock.

gpointer
get_debug_flags(void)
{
staticGOncemy_once=G_ONCE_INIT;
g_once(&my_once,parse_debug_flags,NULL);
returnmy_once.retval;
}

Available since: 2.4

This function is not directly available to language bindings.

once

Type: -

A GOnce structure.

func

Type: -

The GThreadFunc function associated to once. This function is called only once, regardless of the number of times it and its associated GOnce struct are passed to g_once().

arg

Type: -

Data to be passed to func.