Allow calling pure C functions directly

[pannous]

Added use_wrapper to structure NativeSymbol and corresponding methods to enable linking to pure C functions, without prepending wasm_exec_env_t as first argument

example:

int square(int a) {
	return a * a;
}

static NativeSymbol native_symbols[] = {
				{       "square",  (void *) square,  "(i)i", NULL, /*use_wrapper*/ false}
};

[wenyongh]

Added use_wrapper to structure NativeSymbol and corresponding methods to enable linking to pure C functions, without prepending wasm_exec_env_t as first argument

example:

int square(int a) {
	return a * a;
}

static NativeSymbol native_symbols[] = {
				{       "square",  (void *) square,  "(i)i", NULL, /*use_wrapper*/ false}
};

Hi, adding the flag to control whether to pass the exec_env argument to native function or not may introduce more footprint and complexity for runtime, could you please simply add the wrapper function as normal, and call the pure C function in the wrapper function, e.g.:

int square(int a) {
	return a * a;
}

int square_wrapper(wasm_exec_env_t exec_env, int a) {
	return square(a);
}

Thanks.

[pannous]

Well this feature is only 8 lines of code, but if you don't want it for wider adoption that is OK.

I change the title in case others are looking for this functionality too.

[pannous]

There are situations in which wasm-micro-runtime is used as a library and creating ad hoc wrappers is not an option.

[tonibofarull]

If there are no additional checks, maybe it's easier to encapsulate your function with a macro.

[wenyongh]

It is invalid to call pure C function directly since the wrapper function must have an extra argument exec_env which is passed from runtime when calling it.