__BUILTIN_OBJECT_SIZE(3)

__BUILTIN_OBJECT_SIZE(3) | Library Functions Manual | __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.

December 19, 2010 | NetBSD 5.99