Emscripten 'val.h' API allows calling methods of JS objects, however, C++ try-catch won't catch JS exception. Consider this example:
#include <emscripten.h>
#include <emscripten/val.h>
void test(){
string t = "some invalid json";
val v = val::object();
// This C++ try-catch doesn't catch JS exception
try {
v = val::global("JSON").call<val>("parse", t);
cout <<"ok" <<endl;
}
catch(...){
cout <<"failed" <<endl;
}
cout <<"ret" <<endl;
}
The JS exception makes the 'test' function stop and no ok, no failed, no ret printed out. How to catch that JS exception thrown by JSON.parse?
There's 1 issue here but it's still open: https://github.com/emscripten-core/emscripten/issues/11496
Based on documentation:
By default, exception catching is disabled in Emscripten.
You have to enable it with the -fexceptions argument.
Emscripten doesn't seem to be able to catch JS exceptions in C++ yet. Here's a work-around:
// extern_pre.js
function json_parse(str){
try{
return JSON.parse(str);
}
catch(E){
return null;
}
}
// app.cpp
...
val v = val::global("json_parse")(some_str);
Build:
emcc app.cpp -o app.js --bind --extern-pre-js extern_pre.js