Waving sprites with a width and height of 0 crash mkxp-z

[melody-rs]

This is an issue present in mkxp-z but not modshot. I can't for the life of me figure out why, but when SpritePrivate::updateWave() is called and the sprite width and height is 0, this line of code resizes wave.qArray.vertices to a size of 0, which then immediately crashes mkxp-z. This isn't an issue present in modshot (I haven't tested mkxp) and I can't find any significant differences in sprite.cpp that'd cause this.

(log from when i was checking resizes)

Resizing to  4  chunks 
Resizing to  4  chunks 
Resizing to  4  chunks 
Resizing to  4  chunks 
Resizing to  0  chunks 
/usr/include/c++/13.2.1/bits/stl_vector.h:1128: std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::operator[](size_type) [with _Tp = SVertex; _Alloc = std::allocator<SVertex>; reference = SVertex&; size_type = long unsigned int]: Assertion '__n < this->size()' failed.
./oneshot: line 4: 616617 Aborted                 (core dumped) ./oneshot

A pretty hacky fix can be done to fix the bug:

if (width == 0 || height == 0)
{
    wave.active = false;
    return;
}

I don't trust the fix though as it's not really addressing why there's a difference in behavior between modshot and mkxp-z

[WaywardHeart]

That fix looks correct to me. Accessing an entry past the end of a vector causes undefined behavior. Either you're getting (un)lucky and your build of mkxp-z is consistently trying to access memory it shouldn't at that point, or your compiler is being more strict than theirs, assuming you didn't build modshot yourself, that is.

[melody-rs]

¯\_(ツ)_/¯

I did build modshot myself? Weird

[thehatkid]

I have reproduced waving effect on Sprite object that has 0 width or/and 0 height by using spr_obj.src_rect = Rect.new(0, 0, 0, 0).
It only appears when mkxp-z (ModShot in our case) was built in Debug mode with Meson build system --buildtype=debug argument. On Release mode, it does nothing (nor uncaught exception or crash).
However, it is looks unsafe though, attempting to get item index that may be not there.