Skip to main content

Module ABI

This section describes some low-level details of ABI used for module linking and passing values in module-module and module-host schemes.

The best way to see ABI functions is to use the following command:

sh
marine info -i artifacts/greeting.wasm
...
;; Exports
(@interface export "allocate" (func 0))
(@interface export "release_objects" (func 1))
(@interface export "get_result_size" (func 2))
(@interface export "get_result_ptr" (func 3))
(@interface export "set_result_size" (func 4))
(@interface export "set_result_ptr" (func 5))
...
sh
marine info -i artifacts/greeting.wasm
...
;; Exports
(@interface export "allocate" (func 0))
(@interface export "release_objects" (func 1))
(@interface export "get_result_size" (func 2))
(@interface export "get_result_ptr" (func 3))
(@interface export "set_result_size" (func 4))
(@interface export "set_result_ptr" (func 5))
...

All these functions are generated by the SDK and normally a developer shouldn't care about them.

Let's consider all these functions:

allocate​

rust
allocate(elem_count: usize, elem_ty: usize) -> usize
rust
allocate(elem_count: usize, elem_ty: usize) -> usize

Allocate memory enough to place elem_count objects of type elem_ty, returns a pointer to allocated memory region

release_objects​

rust
release_objects()
rust
release_objects()

Removes objects that were saved by generated by the #[marine] macro code to prevent their deletion before parameters passing ends. Usually called by the IT side at the end of passing a function result.

Next four functions are intended to pass results from called functions. They are temporary solution and intended to overcome missing multi-value feature in IT, will be removed in the future with the multi-value passing scheme.

get_result_size​

rust
get_result_size() -> usize
rust
get_result_size() -> usize

Returns a size of a result to the IT operand stack.

get_result_ptr​

rust
get_result_ptr() -> usize
rust
get_result_ptr() -> usize

Returns a pointer to a result to the IT operand stack.

set_result_size​

rust
set_result_size(size: usize)
rust
set_result_size(size: usize)

Set a size of a result to the given value.

set_result_ptr​

rust
set_result_ptr(ptr: usize)
rust
set_result_ptr(ptr: usize)

Set a pointer of a result to the given value.