[bug] : Dereferencing a null pointer allowed for Emscripten xeus-cpp kernel

[mcbarton]

If I run the following in the deployment I will get 0 returned to the notebook.

#include <iostream>

int main() {
    int* ptr = nullptr;
    std::cout << *ptr; 
    return 0;
}
main();

e.g.

Whereas if I was to compile this code

#include <iostream>

int main() {
    int* ptr = nullptr;
    std::cout << *ptr; 
    return 0;
}

and try to run it locally (on a native platform), I get a segmentation fault as expected.

[mcbarton]

This may be helpful https://emscripten.org/docs/debugging/Sanitizers.html as it has an entire section on Catching Null Dereference . They have this section since By default, with Emscripten, dereferencing a null pointer does not immediately cause a segmentation fault, unlike traditional platforms

[anutosh491]

Don't think this is a xeus-cpp-lite bug. I'd suggest closing and opening an issue on emscripten if this sound alarming. I lack the time to do a correctness check so not commenting on what should happen but this is what I see

(xeus-cpp-wasm-build) anutosh491@Anutoshs-MacBook-Air xeus-cpp % cat test.cpp
#include <iostream>

int main() {
    int* ptr = nullptr;
    std::cout << *ptr; 
    return 0;
}
main();%                                                                                                                                                    
(xeus-cpp-wasm-build) anutosh491@Anutoshs-MacBook-Air xeus-cpp % emcc test.cpp -o test.js \
  -sENVIRONMENT=node \
  -sEXIT_RUNTIME=1 \
  -O0 \
  -sASSERTIONS=2
(xeus-cpp-wasm-build) anutosh491@Anutoshs-MacBook-Air xeus-cpp % node test.js
0