class on free aborts on invalid pointer

[andyjsbell]

Using the cpp_class! macro with a simple class aborts on freeing the resource. This is happening on Ubuntu 1804. Code snippet reproducing the issue:

use cpp::cpp;
use cpp::cpp_class;

cpp!{{
    #include <iostream>
    
    using std::string;

    class Test {
    public:
        Test() {
            std::cout << "creating" << std::endl;
        }
        virtual ~Test() {
            std::cout << "destroying" << std::endl;
        }

    protected:
        std::string message; // -> removing this and we don't get the issue
    };
}}

cpp_class!(pub unsafe struct Test as "Test");
impl Test {
    fn new() -> Self {
        unsafe { cpp!([] -> Test as "Test" { return Test(); }) }
    }
}

fn main() {
    let test = Test::new();
}

[ogoffart]

Yeah, cpp_class only work with class that are relocatable.

This is documented there: https://docs.rs/cpp/0.5.5/cpp/macro.cpp_class.html#relocatable-classes

Perhaps the documentation should be more explicit, or extra warning should be in order.

[andyjsbell]

I decided to test this out on OSX and Windows. Interestingly both Windows and OSX did not have the issue.

[ogoffart]

This depends on the implementation of the standard library.

[LastLightSith]

Hi, out of curiosity, why test is relocatable immediately ? it is used only once.

[ogoffart]

Internally it is returned from the Test::new() function so that's one possible relocation (even if it might be optimized)
Also internally in the cpp! macro