Atomically adds val to the value of atomic.
Think of this operation as an atomic version of { tmp = *atomic; *atomic += val; return tmp; }.
This call acts as a full compiler and hardware memory barrier.
a pointer to a [gpointer-sized|gpointer-sized] value
the value to add
the value of atomic before the add, signed
2.30
Atomically adds val to the value of atomic.
Think of this operation as an atomic version of { tmp = *atomic; *atomic += val; return tmp; }.
This call acts as a full compiler and hardware memory barrier.