Uncaught exception when throwing within with_libc lambda - users

30 Mar 2020


      Dear Genodians,
I just stumbled across a not so obvious characteristic of the with_libc lambda. Not so obvious to me, at least.
If I run following code snipped, it will result in a "Error: Uncaught exception of type 'Genode::Exception'":
``` 
try {
    Libc::with_libc([&] () {
    	throw Genode::Exception();
    });
} catch (...) {
    Genode::log("caught libc exception");
}
```
I didn't find any documentation regarding the with_libc lambda in combination with exceptions.
Is this expected behavior?
What would be the right pattern to forward the exception to a pure Genode environment e.g. across RPC boundaries?
I could think of following pattern:
``` 
bool libc_exception_thrown = false;
Libc::with_libc([&] () {
    try {
    	throw Genode::Exception();
    } catch (...) {
    	Genode::log("caught libc exception");
    	libc_exception_thrown = true;
    }
});
if (libc_exception_thrown) {
    throw My_rpc_exception();
}
```
However, it does not look like the most elegant solution...
Cheers,
Sid