offsetof Macro

Retrieves the offset of a member from the beginning of its parent structure.

Syntax

size_t offsetof(
   structName,
   memberName
);

Parameters

structName
Name of the parent data structure.

memberName
Name of the member in the parent data structure for which to determine the offset.

Return value

offsetof returns the offset in bytes of the specified member from the beginning of its parent data structure. It's undefined for bit fields.

Remarks

The offsetof macro returns the offset in bytes of memberName from the beginning of the structure specified by structName as a value of type size_t. You can specify types with the struct keyword.

Note

offsetof is not a function and cannot be described using a C prototype.

Requirements

Routine	Required header
offsetof	<stddef.h>

For more compatibility information, see Compatibility.

Libraries

All versions of the C run-time libraries.

See also

Memory allocation