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chore: update doc/dev/ffi.md after #9088 (#9112)

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Cameron Zwarich 2025-06-30 18:00:59 -07:00 • committed by GitHub
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@ -68,7 +68,7 @@ The memory order of the fields is derived from the types and order of the fields
* Fields of type `USize`
* Other scalar fields, in decreasing order by size
Within each group the fields are ordered in declaration order. **Warning**: Trivial wrapper types still count toward a field being treated as non-scalar for this purpose.
Within each group the fields are ordered in declaration order. Trivial wrapper types count as their underlying wrapped type for this purpose.
* To access fields of the first kind, use `lean_ctor_get(val, i)` to get the `i`th non-scalar field.
* To access `USize` fields, use `lean_ctor_get_usize(val, n+i)` to get the `i`th usize field and `n` is the total number of fields of the first kind.
@ -80,32 +80,32 @@ structure S where
ptr_1 : Array Nat
usize_1 : USize
sc64_1 : UInt64
ptr_2 : { x : UInt64 // x > 0 } -- wrappers don't count as scalars
sc64_2 : Float -- `Float` is 64 bit
sc64_2 : { x : UInt64 // x > 0 } -- wrappers of scalars count as scalars
sc64_3 : Float -- `Float` is 64 bit
sc8_1 : Bool
sc16_1 : UInt16
sc8_2 : UInt8
sc64_3 : UInt64
sc64_4 : UInt64
usize_2 : USize
ptr_3 : Char -- trivial wrapper around `UInt32`
sc32_1 : UInt32
sc32_1 : Char -- trivial wrapper around `UInt32`
sc32_2 : UInt32
sc16_2 : UInt16
```
would get re-sorted into the following memory order:
* `S.ptr_1` - `lean_ctor_get(val, 0)`
* `S.ptr_2` - `lean_ctor_get(val, 1)`
* `S.ptr_3` - `lean_ctor_get(val, 2)`
* `S.usize_1` - `lean_ctor_get_usize(val, 3)`
* `S.usize_2` - `lean_ctor_get_usize(val, 4)`
* `S.sc64_1` - `lean_ctor_get_uint64(val, sizeof(void*)*5)`
* `S.sc64_2` - `lean_ctor_get_float(val, sizeof(void*)*5 + 8)`
* `S.sc64_3` - `lean_ctor_get_uint64(val, sizeof(void*)*5 + 16)`
* `S.sc32_1` - `lean_ctor_get_uint32(val, sizeof(void*)*5 + 24)`
* `S.sc16_1` - `lean_ctor_get_uint16(val, sizeof(void*)*5 + 28)`
* `S.sc16_2` - `lean_ctor_get_uint16(val, sizeof(void*)*5 + 30)`
* `S.sc8_1` - `lean_ctor_get_uint8(val, sizeof(void*)*5 + 32)`
* `S.sc8_2` - `lean_ctor_get_uint8(val, sizeof(void*)*5 + 33)`
* `S.usize_1` - `lean_ctor_get_usize(val, 1)`
* `S.usize_2` - `lean_ctor_get_usize(val, 2)`
* `S.sc64_1` - `lean_ctor_get_uint64(val, sizeof(void*)*3)`
* `S.sc64_2` - `lean_ctor_get_uint64(val, sizeof(void*)*3 + 8)`
* `S.sc64_3` - `lean_ctor_get_float(val, sizeof(void*)*3 + 16)`
* `S.sc64_4` - `lean_ctor_get_uint64(val, sizeof(void*)*3 + 24)`
* `S.sc32_1` - `lean_ctor_get_uint32(val, sizeof(void*)*3 + 32)`
* `S.sc32_2` - `lean_ctor_get_uint32(val, sizeof(void*)*3 + 36)`
* `S.sc16_1` - `lean_ctor_get_uint16(val, sizeof(void*)*3 + 40)`
* `S.sc16_2` - `lean_ctor_get_uint16(val, sizeof(void*)*3 + 42)`
* `S.sc8_1` - `lean_ctor_get_uint8(val, sizeof(void*)*3 + 44)`
* `S.sc8_2` - `lean_ctor_get_uint8(val, sizeof(void*)*3 + 45)`
### Borrowing