offsetof Macro

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

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 as a value of type size_t. It is undefined for bit fields.

Remarks

The offsetof macro returns the offset in bytes of memberName from the beginning of the structure specified by structName. 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 additional compatibility information, see Compatibility in the Introduction.

Libraries

All versions of the C run-time libraries.

See Also

Reference

Memory Allocation