Attribute Macro padding_struct 

#[padding_struct]

Procedural macro to automatically add padding fields to a #[repr(C)] struct.

This macro generates two structs:

1. A reference struct (prefixed and suffixed with __) containing the original fields without padding.
2. A padded struct (using the original name) with __padN padding fields after each original field.

Padding Calculation Rules

• For non-last fields: padding size = next field’s offset - current field’s offset - current field’s size.
• For the last field: padding size = struct total size - current field’s offset - current field’s size.

Requirements

• The struct must have a #[repr(C)] attribute.
• The struct must have named fields.

Examples

use padding_struct::padding_struct;

#[repr(C)]
#[padding_struct]
struct MyStruct {
    a: u8,
    b: u32,
}

This generates code equivalent to:

use core::mem::offset_of;

#[repr(C)]
struct __MyStruct__ {
    a: u8,
    b: u32,
}

#[repr(C)]
struct MyStruct {
    a: u8,
    pub __pad1:
        [u8; const { offset_of!(__MyStruct__, b) - offset_of!(__MyStruct__, a) - size_of::<u8>() }],
    b: u32,
    pub __pad2:
        [u8; const { size_of::<__MyStruct__>() - offset_of!(__MyStruct__, b) - size_of::<u32>() }],
}