We have known memory leaks with extern types. The idea is to change
the code so that extern types can hold/own data. This patch does that.
A `wasm_externtype_t` holds a `WasmExternType` enum. This enum owns
sibling types such as `WasmFunctionType`, `WasmGlobalType`,
`WasmTableType` and `WasmMemoryType`. It is those structures that ows
the extern types data, like `params` and `results` as
`wasm_valtype_vec_t` for `WasmFunctionType`. That way, for example,
`wasm_functype_t` can return a pointer to these vec which it owns.
A `wasm_externtype_t` continues to be transmuted to `wasm_functype_t`
etc. Nothing changes on that side.
`assert.h` does nothing when the code is compiled in release
mode. That's not what we want :-). Let's reimplement `assert` as
`wasmer_assert`, which is close to the original `assert` function.
There is no memory leaks with those functions as far as I understand this code.
Check the following code as a fun playground, which reproduces a
typical use of `wasm_functype_params` or `_results` that both return a
`wasm_valtype_vec_t`:
```rust
struct wasm_valtype_t { x: u8 }
impl Drop for wasm_valtype_t {
fn drop(&mut self) {
println!("wasm_valtype_t {{ {} }} dropped!", self.x)
}
}
struct wasm_valtype_vec_t {
size: usize,
data: *mut *mut wasm_valtype_t,
}
unsafe fn wasm_valtype_vec_delete(ptr: *mut wasm_valtype_vec_t) {
let vec = &mut *ptr;
if !vec.data.is_null() {
let data: Vec<*mut wasm_valtype_t> = Vec::from_raw_parts(vec.data, vec.size, vec.size);
let _data: Vec<Box<wasm_valtype_t>> = ::std::mem::transmute(data);
vec.data = ::std::ptr::null_mut();
vec.size = 0;
}
}
fn main() {
let x = Box::into_raw(Box::new(wasm_valtype_t { x: 1 }));
let y = Box::into_raw(Box::new(wasm_valtype_t { x: 2 }));
let z = Box::into_raw(Box::new(wasm_valtype_t { x: 3 }));
let mut valtypes: Vec<*mut wasm_valtype_t> = vec![x, y, z];
let vec = Box::into_raw(Box::new(wasm_valtype_vec_t {
size: valtypes.len(),
data: valtypes.as_mut_ptr(),
}));
::std::mem::forget(valtypes);
unsafe { wasm_valtype_vec_delete(vec as *mut _); }
}
```
It prints:
```
wasm_valtype_t { 1 } dropped!
wasm_valtype_t { 2 } dropped!
wasm_valtype_t { 3 } dropped!
```
All `wasm_valtype_t` are dropped correctly. Since they contain an
owned value, there is no leaks here.
Remove the `build.rs` hack to add helper functions that are used only
in our tests. Now the tests can use the `tests/wasmer_wasm.h` file,
which simplifies the test workflow: No need to hack the build script
or anything if we want to add a helper function.
It's very similar to `wasm_name_new_from_string` but for
`wasm_byte_vec_t`. It does not make sense to get that in the standard,
but it's very useful when writing tests.
