Add function to retrieve function name from wasm_frame_t

[fschutt]

Fixes #3166.

[fschutt]

Should be done like https://docs.wasmtime.dev/c-api/trap_8h_source.html

[fschutt]

@syrusakbary @Michael-F-Bryan review + merge?

[Michael-F-Bryan]

It doesn't look like we provide a function which gives you a *const c_char from a *const wasm_name_t. Does that mean we expect the caller to cast a wasm_name_t to a *const char so they can read it?

Jumping around wasmtime's docs, it seems like wasm_name_t is just a typedef for wasm_byte_vec_t, which is pretty much the C version of an &str reference pointing into our wasm_frame_t.

I'm not sure whether frame.info.function_name() and frame.info.module_name() return borrowed &strs or owned Strings, but if they're borrowed it means we can drop the wasm_name_delete() destructor.

[fschutt]

I'm not sure whether frame.info.function_name() and frame.info.module_name() return borrowed &strs or owned Strings, but if they're borrowed it means we can drop the wasm_name_delete() destructor.

It doesn't matter because we need to convert them to CString anyway (trailing 0). So we need to allocate.

Does that mean we expect the caller to cast a wasm_name_t to a *const char so they can read it?

No, it returns a wasm_name_t, which has to be deleted by the user because it allocates Rust memory (see above). So I wanted to make that clear in the API, so that we have wasm_frame_module_name and wasm_frame_function_name for creation of the wasm_name_t and wasm_name_delete for deletion. The API is not that hard.

Users can print printf("%s", wasm_name_t.name); just like normal.

[Michael-F-Bryan]

bors r+

[bors]

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