atomic_is_lock_free
| Defined in header <stdatomic.h>
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| _Bool atomic_is_lock_free( const volatile A* obj ); |
(since C11) | |
Determines if the atomic operations on all objects of the type A (the type of the object pointed to by obj) are lock-free. In any given program execution, the result of calling atomic_is_lock_free is the same for all pointers of the same type.
This is a generic function defined for all atomic object types A. The argument is pointer to a volatile atomic type to accept addresses of both non-volatile and volatile (e.g. memory-mapped I/O) atomic objects, and volatile semantic is preserved when applying this operation to volatile atomic objects.
It is unspecified whether the name of a generic function is a macro or an identifier declared with external linkage. If a macro definition is suppressed in order to access an actual function (e.g. parenthesized like (atomic_is_lock_free)(...)), or a program defines an external identifier with the name of a generic function, the behavior is undefined.
Parameters
| obj | - | pointer to the atomic object to inspect |
Return value
true if the operations on all objects of the type A are lock-free, false otherwise.
Notes
C11, as published, specified that this function is per-object, not per-type. This was corrected by DR 465.
Example
#include <stdio.h> #include <stdatomic.h> _Atomic struct A { int a[100]; } a; _Atomic struct B { int x, y; } b; int main(void) { printf("_Atomic struct A is lock free? %s\n", atomic_is_lock_free(&a) ? "true" : "false"); printf("_Atomic struct B is lock free? %s\n", atomic_is_lock_free(&b) ? "true" : "false"); }
Possible output:
_Atomic struct A is lock free? false _Atomic struct B is lock free? true
References
- C11 standard (ISO/IEC 9899:2011):
- 7.17.5.1 The atomic_is_lock_free generic function (p: 280)
See also
| indicates that the given atomic type is lock-free (macro constant) |