eea75e7862
`wasm_trap_new` expects a `wasm_message_t`. It's a type alias to `wasm_name_t` with the exception that it represents a null-terminated string. When calling `wasm_trap_new`, no check was present to ensure the string was well-formed. That's a first issue. But in the best scenario, the string was correctly formed and was null-terminated. This string was transformed to a Rust `String` —with the null byte!— and passed to `RuntimeError`. Then in `wasm_trap_message`, another null byte was pushed at the end of the message. It's been introduced in https://github.com/wasmerio/wasmer/pull/1947. It results in a doubly-null-terminated string, which is incorrect. This patch does the following: 1. It checks that the string given to `wasm_trap_new` contains a null-terminated string or not, and will act accordingly. Note that it's possible to pass a non-null-terminated string, and it will still work because this detail is vicious. The idea is to get a well-formed `RuntimeError` in anycase. * If no null byte is found, the string is passed to `RuntimeError` as a valid Rust string, * If a null byte is found at the end of the string, a new string is passed to `RuntimeError` but without the final null byte, * If a null byte is found but not at the end, it's considered as an error, * If the string contains invalid UTF-8 bytes, it's considered as an error. 2. It updates `wasm_trap_message` to always add a null byte at the end of the returned owned string. 3. It adds test cases when passing a null-terminated or a non-null-terminated string to `wasm_trap_new` and to compare the results to `wasm_trap_message`.
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.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/crates/wasmer_c_api/index.html
Here is a simple example to use the C API:
#include <stdio.h>
#include "wasmer.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);
wasm_byte_vec_delete(&wat);
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_extern_vec_delete(&exports);
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).