70c31068be
First, let's no longer derive from `Default` for `wasi_config_t`. By default, we want to inherit `stdin`, `stdout` and `stderr`. The default for `bool` is `false`; we want `true` here. Second, let's update `wasi_config_new` to correctly set `inherit_*` fields to `true`. Third, lets' create `wasi_config_capture_*` functions. By default, `std*` are inherited, so we need functions to capture them. That's the new feature this patch introduces. The `wasi_config_inherit_*` functions are kept for the sake of backward compatibility. Ideally, we would want an API like `wasi_config_capture_*(capture: bool)`, but it would duplicate the API somehow. Fourth, let's fix `wasi_env_new`. We want to capture `stdout` and `stderr` if and only if the `inherit_*` fields are set to `false`. There was bug here. That's why everything was working correctly by the way: `bool::default()` is `false`, and we have this inverted condition here, so everything was working as expected because of a double error. The only bug was that it wasn't possible to capture `std*` before.
wasmer-c-api 
This crate exposes a C and a C++ API for the Wasmer runtime. It also fully supports the wasm-c-api common API.
Usage
Once you install Wasmer in your system, the shared object files and the headers are available inside the Wasmer installed path.
$WASMER_DIR/
lib/
libwasmer.{so,dylib,dll}
include/
wasm.h
wasmer.h
wasmer.hh
wasmer_wasm.h
Wasmer binary also ships with wasmer-config
an utility tool that outputs config information needed to compile programs which use Wasmer.
The full C API documentation can be found here: https://wasmerio.github.io/wasmer/c-api/
Here is a simple example to use the C API:
#include <stdio.h>
#include "wasmer_wasm.h"
int main(int argc, const char* argv[]) {
const char *wat_string =
"(module\n"
" (type $sum_t (func (param i32 i32) (result i32)))\n"
" (func $sum_f (type $sum_t) (param $x i32) (param $y i32) (result i32)\n"
" local.get $x\n"
" local.get $y\n"
" i32.add)\n"
" (export \"sum\" (func $sum_f)))";
wasm_byte_vec_t wat;
wasm_byte_vec_new(&wat, strlen(wat_string), wat_string);
wasm_byte_vec_t wasm_bytes;
wat2wasm(&wat, &wasm_bytes);
printf("Creating the store...\n");
wasm_engine_t* engine = wasm_engine_new();
wasm_store_t* store = wasm_store_new(engine);
printf("Compiling module...\n");
wasm_module_t* module = wasm_module_new(store, &wasm_bytes);
if (!module) {
printf("> Error compiling module!\n");
return 1;
}
wasm_byte_vec_delete(&wasm_bytes);
printf("Creating imports...\n");
wasm_extern_vec_t import_object = WASM_EMPTY_VEC;
printf("Instantiating module...\n");
wasm_instance_t* instance = wasm_instance_new(store, module, &import_object, NULL);
if (!instance) {
printf("> Error instantiating module!\n");
return 1;
}
printf("Retrieving exports...\n");
wasm_extern_vec_t exports;
wasm_instance_exports(instance, &exports);
if (exports.size == 0) {
printf("> Error accessing exports!\n");
return 1;
}
printf("Retrieving the `sum` function...\n");
wasm_func_t* sum_func = wasm_extern_as_func(exports.data[0]);
if (sum_func == NULL) {
printf("> Failed to get the `sum` function!\n");
return 1;
}
printf("Calling `sum` function...\n");
wasm_val_t args_val[2] = { WASM_I32_VAL(3), WASM_I32_VAL(4) };
wasm_val_t results_val[1] = { WASM_INIT_VAL };
wasm_val_vec_t args = WASM_ARRAY_VEC(args_val);
wasm_val_vec_t results = WASM_ARRAY_VEC(results_val);
if (wasm_func_call(sum_func, &args, &results)) {
printf("> Error calling the `sum` function!\n");
return 1;
}
printf("Results of `sum`: %d\n", results_val[0].of.i32);
wasm_func_delete(sum_func);
wasm_module_delete(module);
wasm_instance_delete(instance);
wasm_store_delete(store);
wasm_engine_delete(engine);
}
Building
You can compile Wasmer shared library from source:
make build-capi
This will generate the shared library (depending on your system):
- Windows:
target/release/libwasmer_c_api.dll - macOS:
target/release/libwasmer_runtime_c_api.dylib - Linux:
target/release/libwasmer_runtime_c_api.so
If you want to generate the library and headers in a friendly format as shown in Usage, you can execute the following in Wasmer root:
make package-capi
This command will generate a package directory, that you can then use easily in the Wasmer C API examples.
Testing
Tests are run using the release build of the library. If you make changes or compile with non-default features, please ensure you rebuild in release mode for the tests to see the changes.
To run all the full suite of tests, enter Wasmer root directory and run the following commands:
$ make test-capi
wasmer config
wasmer config output various configuration information needed to compile programs which use Wasmer.
wasmer config --pkg-config
It outputs the necessary details for compiling and linking a program to Wasmer,
using the pkg-config format:
$ wasmer config --pkg-config > $PKG_CONFIG_PATH/wasmer.pc
wasmer config --includedir
Directory containing Wasmer headers:
$ wasmer config --includedir
/users/myuser/.wasmer/include
wasmer config --libdir
Directory containing Wasmer libraries:
$ wasmer config --libdir
/users/myuser/.wasmer/lib
wasmer config --libs
Libraries needed to link against Wasmer components:
$ wasmer config --libs
-L/Users/myuser/.wasmer/lib -lwasmer
wasmer config --libs
Libraries needed to link against Wasmer components:
$ wasmer config --cflags
-I/Users/myuser/.wasmer/include/wasmer
License
Wasmer is primarily distributed under the terms of the MIT license (LICENSE).