Left shift button crashing SDL Code Events in Android

I think I’m using SDL 2.0.10 for Android

if (event.type == SDL_KEYDOWN)
bKeysHeld[event.key.keysym.sym] = true;

It works fine with letters and numbers, but the shift key crashs it, also few other buttons, like enter.

anyone have any idea why it’s crashing?

event.key.keysym.sym is of the type SDL_Keycode which is essentially a signed 32-bit integer. I’m assuming that bKeysHeld is a fixed size array that doesn’t have the space to hold a billion+ entries (that would be very silly). The left shift key has the value SDLK_LSHIFT, which is done with a macro on the SDL_Scancode going by the name SDL_SCANCODE_LSHIFT (with a value of 225). The macro SDL_SCANCODE_TO_KEYCODE sets the second highest bit (highest non-sign bit) to 1 and ORs this with the scancode, producing the expression (1 << 30) | 225 which has the value 1073742049 or just over a billion. This means you’re trying to write to a location that is around 4GiB past the start of your array, resulting in a buffer overflow.

If you want similar semantics to what you’re currently doing, you could for instance use a hash map of booleans instead of an array, or a hash set of keysyms where you either add or remove entries as you come across key events.

Hope this helps.

Or you could just use the event.key.keysym.scancode field instead and make bKeysHeld have its size be SDL_NUM_SCANCODES. That would require the fewest changes to your code.

I don’t get it works fine for the smaller buttons, I found this.

" The value of event.key.keysym.sym is wrong for sdl.SDL_KEYDOWN/sdl.SDL_KEYUP events on ARM64/postmarketOS/sdl2-2.0.12-r1. For example, this is what I get for a t key: 1073742095, when it should be 116 according to SDL_keycode.h.

This is on an ARM64 device running postmarketOS (based on Alpine Linux) with sdl2-2.0.12-r1. It works fine on my Fedora 32 x64 machine with its SDL2 2.0.12-1.fc32, so I do wonder if this is a bug with PySDL2’s assumption of how the event struct is laid out on ARM64 platforms? At least that is my best guess as to what the issue could be.

Edit: also yes, that means all key input other than SDL_TEXTINPUT is currently unusable on that platform which is a bit of a shame"

I did this and it worked

 if (event.type == SDL_KEYDOWN)
        //KeysHeld[event.key.keysym.sym] = true;
        if(event.key.keysym.sym == SDLK_LSHIFT)
            bLeftShift = true;