Segfault with set_use_custom_draw

[tjkirch]

That said, set_use_custom_draw does seem like the right approach for this. If you can reproduce the segfaults we should figure out why they occur.

Originally posted by @rtsuk in https://github.com/pd-rs/crankstart/issues/35#issuecomment-1483709249

---

Here's a minimal reproduction:

#![no_std]
extern crate alloc;

use {
    alloc::boxed::Box,
    anyhow::Error,
    crankstart::{
        crankstart_game,
        graphics::Graphics,
        sprite::{Sprite, SpriteManager},
        Game, Playdate,
    },
    crankstart_sys::{LCDBitmapFlip, PDRect},
};

struct State {
    // If the sprite is not stored, the crash doesn't happen
    _sprite: Sprite,
}

impl State {
    pub fn new(_playdate: &Playdate) -> Result<Box<Self>, Error> {
        // Load an image, assign it to a custom-draw sprite, add the sprite.
        // Crash doesn't happen unless a bitmap is assigned to the sprite.
        let bitmap = Graphics::get().load_bitmap("graphics/wedge")?;
        let sprite_manager = SpriteManager::get_mut();
        let mut sprite = sprite_manager.new_sprite()?;
        // No crash unless it's custom-draw.
        sprite.set_use_custom_draw()?;
        sprite.set_image(bitmap, LCDBitmapFlip::kBitmapUnflipped)?;
        sprite_manager.add_sprite(&sprite)?;
        Ok(Box::new(Self { _sprite: sprite }))
    }
}

impl Game for State {
    fn update(&mut self, _playdate: &mut Playdate) -> Result<(), Error> {
        Ok(())
    }

    fn update_sprite(&mut self, _: &mut Sprite, _: &mut Playdate) -> Result<(), Error> {
        Ok(())
    }

    // Same crash happens with or without this definition:
    fn draw_sprite(&self, _: &Sprite, _: &PDRect, _: &PDRect, _: &Playdate) -> Result<(), Error> {
        Ok(())
    }
}

crankstart_game!(State);

The result:

Loading C API game: target/Golf Date.pdx/pdex.so
16:23:47: Loading: OK

Thread 1 "PlaydateSimulat" received signal SIGSEGV, Segmentation fault.
0x0000555555968c88 in _compositeRow ()
(gdb) bt
#0  0x0000555555968c88 in _compositeRow ()
#1  0x00005555559735da in LCDBitmap_drawBitmap ()
#2  0x0000555555980d70 in LCD_drawBitmap ()
#3  0x00005555559828b9 in LCDSprite_draw ()
#4  0x000055555597d71c in LCDDisplayList_drawScreenRect ()
Dwarf Error: Cannot find DIE at 0xccf referenced from DIE at 0x1349f [in module target/Golf Date.pdx/pdex.so]

The backtrace is the same whether I define draw_sprite or not. Is it not being hooked up properly? Or is draw_sprite required to take some action that the SDK depends upon having happened?

[rtsuk]

I don't recall seeing any C examples that use custom draw and then also set an image on the sprite. I'm not sure what the Playdate will do in that case.

[tjkirch]

If it's just something that shouldn't be done, I could make a doc comment :) A more mechanical fix might involve a bool on Sprite that tracks whether set_use_custom_draw has been called and whether an image has been set, failing if one or the other has already happened...

[rtsuk]

The backtrace suggests the crash is in the Playdate code, so maybe that's not a good thing to do? One could write a C version and see what happens. That, or ask on the forums.