Dereferencing Headless::joystick1 is UB

[kpp]

nes-emulator/src/headless.rs

Line 117 in 0b9e321

unsafe { (*self.joystick1).set_buttons(button_mask) };

https://doc.rust-lang.org/reference/behavior-considered-undefined.html : Dereferencing a null or dangling raw pointer.

Headless::joystick1/2 are initialized with:

impl Headless {
    fn command_load_rom(&mut self) {
        let mut record_tas = self.read_byte();
        let filename = self.read_length_string();
        let mut joystick1 = Box::new(Joystick::new());
        let mut joystick2 = Box::new(Joystick::new());
        self.joystick1 = &mut *joystick1;
        self.joystick2 = &mut *joystick2;
        ...
        // drop joystick1 joystick2
        // Headless::joystick1/2 are dangling pointers since joystick1 joystick2 are freed
    }

[MichaelBurge]

joystick1 and joystick2 aren't freed - their ownership is transferred to the Nes object created in the same function.

nes.rs even has this line:

nes-emulator/src/nes.rs

Line 156 in 0b9e321

mapper.map_address_space(0x4017, 0x4017, _joystick2, false); // TODO -- Transfers ownership of joystick2 so it isn't deallocated

because even though the second controller isn't used, its ownership needs to be transferred to prevent the exact problem you describe.

[kpp]

Right