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feat(c-api) Implement the traps argument of wasm_instance_new #1761

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merged 7 commits into from
Oct 30, 2020
Merged

feat(c-api) Implement the traps argument of wasm_instance_new #1761

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a2d96d9
feat(c-api) Implement the `traps` argument of `wasm_instance_new`.
Hywan Oct 26, 2020
38c57e1
test(c-api) Enable the `wasm-c-api-start` test.
Hywan Oct 26, 2020
246b7d2
doc(changelog) Add #1761.
Hywan Oct 26, 2020
4521813
fix(c-api) Remove a `debug_assert` macro.
Hywan Oct 27, 2020
4102dcb
feat(c-api) Shrink vector of traps.
Hywan Oct 27, 2020
9583a91
fix(c-api) `wasm_trap_t**` in `wasm_instance_new` does not represent …
Hywan Oct 30, 2020
bdb0dc7
Merge branch 'master' into feat-c-api-instance-new-traps
Hywan Oct 30, 2020
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2 changes: 2 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -8,8 +8,10 @@
## **[Unreleased]**

- [#1710](https://github.com/wasmerio/wasmer/pull/1710) Memory for function call trampolines is now owned by the Artifact.

### Added

- [#1761](https://github.com/wasmerio/wasmer/pull/1761) Implement the `wasm_trap_t**` argument of `wasm_instance_new` in the Wasm C API.
- [#1741](https://github.com/wasmerio/wasmer/pull/1741) Implement `wasm_memory_type` in the Wasm C API.
- [#1736](https://github.com/wasmerio/wasmer/pull/1736) Implement `wasm_global_type` in the Wasm C API.
- [#1699](https://github.com/wasmerio/wasmer/pull/1699) Update `wasm.h` to its latest version.
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34 changes: 30 additions & 4 deletions lib/c-api/src/wasm_c_api/instance.rs
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Expand Up @@ -5,7 +5,7 @@ use super::trap::wasm_trap_t;
use crate::ordered_resolver::OrderedResolver;
use std::mem;
use std::sync::Arc;
use wasmer::{Extern, Instance};
use wasmer::{Extern, Instance, InstantiationError};

#[allow(non_camel_case_types)]
pub struct wasm_instance_t {
Expand All @@ -17,8 +17,7 @@ pub unsafe extern "C" fn wasm_instance_new(
_store: &wasm_store_t,
module: &wasm_module_t,
imports: &wasm_extern_vec_t,
// own
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Might be useful to put this comment back if it's correct, otherwise it's not clear what the ownership is of *mut *mut, own means we're responsible for freeing it I believe

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We can't own it. We can't free it. The start.c example explicitely drops the trap value:

wasmer/lib/c-api/tests/wasm_c_api/wasm-c-api/example/start.c

Lines 58 to 60 in 86f3438

own wasm_trap_t* trap = NULL;
own wasm_instance_t* instance =
wasm_instance_new(store, module, &imports, &trap);

and later:

wasmer/lib/c-api/tests/wasm_c_api/wasm-c-api/example/start.c

Line 95 in 86f3438

wasm_trap_delete(trap);

I believe that the value is owned by the caller, not by the callee.

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Huh, own wasm_trap_t** is weird in the context of using arguments as outputs.

It seems like there's no need for the Vec at all then, this just seems to be a double pointer for the sake of setting a trap*

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So wasm_trap_t** must not be interpreted as an array of wasm_trap_t*, hmm. Let's fix that then.

_traps: *mut *mut wasm_trap_t,
traps: *mut *mut wasm_trap_t,
) -> Option<Box<wasm_instance_t>> {
let wasm_module = &module.inner;
let module_imports = wasm_module.imports();
Expand All @@ -32,7 +31,34 @@ pub unsafe extern "C" fn wasm_instance_new(
.cloned()
.collect();

let instance = Arc::new(c_try!(Instance::new(wasm_module, &resolver)));
let instance = match Instance::new(wasm_module, &resolver) {
Ok(instance) => Arc::new(instance),

Err(InstantiationError::Link(link_error)) => {
crate::error::update_last_error(link_error);

return None;
}

Err(InstantiationError::Start(runtime_error)) => {
let pointer = {
let trap: Box<wasm_trap_t> = Box::new(runtime_error.into());
let mut traps: Vec<*mut wasm_trap_t> = Vec::with_capacity(1);
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traps.push(Box::into_raw(trap));
traps.shrink_to_fit();

let pointer = traps.as_mut_ptr();
mem::forget(traps);
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pointer
};

*traps = *pointer;
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return None;
}
};

Some(Box::new(wasm_instance_t { inner: instance }))
}

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14 changes: 7 additions & 7 deletions lib/c-api/tests/wasm_c_api/CMakeLists.txt
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Expand Up @@ -11,7 +11,7 @@ add_executable(wasm-c-api-hello wasm-c-api/example/hello.c)
#add_executable(wasm-c-api-multi wasm-c-api/example/multi.c)
add_executable(wasm-c-api-reflect wasm-c-api/example/reflect.c)
add_executable(wasm-c-api-serialize wasm-c-api/example/serialize.c)
#add_executable(wasm-c-api-start wasm-c-api/example/start.c)
add_executable(wasm-c-api-start wasm-c-api/example/start.c)
#add_executable(wasm-c-api-table wasm-c-api/example/table.c)
#add_executable(wasm-c-api-threads wasm-c-api/example/threads.c)
add_executable(wasm-c-api-trap wasm-c-api/example/trap.c)
Expand Down Expand Up @@ -106,12 +106,12 @@ add_test(NAME wasm-c-api-serialize
WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/wasm-c-api/example/
)

#target_link_libraries(wasm-c-api-start general ${WASMER_LIB})
#target_compile_options(wasm-c-api-start PRIVATE ${COMPILER_OPTIONS})
#add_test(NAME wasm-c-api-start
# COMMAND wasm-c-api-start
# WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/wasm-c-api/example/
#)
target_link_libraries(wasm-c-api-start general ${WASMER_LIB})
target_compile_options(wasm-c-api-start PRIVATE ${COMPILER_OPTIONS})
add_test(NAME wasm-c-api-start
COMMAND wasm-c-api-start
WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/wasm-c-api/example/
)

#target_link_libraries(wasm-c-api-table general ${WASMER_LIB})
#target_compile_options(wasm-c-api-table PRIVATE ${COMPILER_OPTIONS})
Expand Down