[Gulliby]

Requested by gulliby

Before

The struct description language accepted ptr for pointer-sized fields, but there was no integer type that follows the platform pointer width, so lengths and offsets such as size_t or Rust's usize had to be written as ptr or as a fixed-width integer.

After

usize and isize are accepted wherever ptr is, including array elements and nested structs. Both have exactly the size and alignment of ptr: 8 and 8 under lp64, 4 and 4 under ilp32. Other names such as size_t are still unknown types. For this struct:

struct Buf {
    u8 tag;
    usize len;
    isize off;
    u16 flags;
}

structpad layout --abi ilp32 ffi.sp prints:

struct Buf: size 16, align 4, padding 5
offset   size  field
     0      1  tag: u8
     1      3  (padding)
     4      4  len: usize
     8      4  off: isize
    12      2  flags: u16
    14      2  (padding)

How

• src/structpad/types.py: two rows added to PRIMITIVE_TYPES right after ptr, with the same numbers as ptr. The parser, layout, suggestions and renderers already read this table, so nothing else changes.
• tests/test_pointer_ints.py: five new tests (primitive sizes, layout under both ABIs, suggest and check, JSON output and the unknown size_t). The existing 145 tests are untouched; the suite now has 150.
• README.md: a short paragraph and an example in the Input language section.