__BUILTIN_OBJECT_SIZE(3)

NAME
__builtin_object_size - return the size of the given object

SYNOPSIS
size_t
__builtin_object_size(void *ptr, int type);

DESCRIPTION
The __builtin_object_size() function is a gcc(1) built-in function that returns the size of the ptr object if known at compile time and the object does not have any side effects.

RETURN VALUES
If the size of the object is not known or it has side effects the __builtin_object_size() function returns:

(size_t)-1
    for type 0 and 1.

(size_t)0
    for type 2 and 3.

If the size of the object is known, then the __builtin_object_size() function returns the maximum size of all the objects that the compiler knows that they can be pointed to by ptr when type 2 == 0, and the minimum size when type 2 != 0.

SEE ALSO
gcc(1), __builtin_return_address(3), attribute(3), ssp(3)

HISTORY
The __builtin_object_size() appeared in GCC 4.1.

CAVEATS
This is a non-standard, compiler-specific extension.