Possible cart data race-condition

Wed, 05 Jun 2024 05:50:10 UTC

Hello, I reported this race condition on itch.io but got no replies so I am posting it again here, in case somebody stumbles on it.

This problem happens when the cart data is in use and the cartridge is quickly restarted.

Consider the following code:

value = 0
frame = 0
function _init()
  cartdata("race_condition")
  value = dget(0)
  dset(0,0) -- set value to 0 for next reload with ctrl+r
end
function _update()
  if btnp(5) then
    dset(0, (value+1)%10) -- increase value by 1
    run() -- reset cartridge
  end
  frame += 1
end
function _draw()
  cls()
  print("current value: "..value, value+1)
  print("frame: "..frame)
end

If you look at it, the expected behavior would be that:

If you press X, the stored value should increase by 1 (modulus 10) and then the cartridge should restart and load that value.
If you reset with Ctrl+R, no value is set so it should be reset to 0 because of the dset(0, 0) at the end of the init.

Notice however, that if you run the cartridge and press X, there are 3 possible outcomes:

Value gets reset to 0.
Value stays the same.
Value increases by 1 as intended, but this only seems to happen if the cartridge ran for more than 60 frames.

So my belief is that there is a race condition between the dset() calls of the different times the cartridge is reset, and they fight to write in the cart data.

This behavior seems independent of the target platform, you can try it here:

racecond_test

by autopawn

[Click to Play]

murder_drones_virtual_training

Sun, 24 Mar 2024 21:53:05 UTC

Murder Drones Virtual Training 1.2.1

by autopawn

[Click to Play]

This is a hard action-platformer fangame based on the Murder Drones indie animated series by GLITCH.

You play as a new disassembly drone that has to complete his training in a virtual environment.

Controls

Arrow keys to move.
[X] to flutter.
[C] to shoot and detonate rockets (when available).
[↓] to perform a dive maneuver.
[Enter] for additional options.

Credits

Autopawn (Discord: autopawn)
Remi Mixer (Discord: remimixer)
Crjönch (Discord: crjonch, Twitter: @Slimyappraisal)
Miszuk (Discord: miszukuwu)
Label character illustrations by @marshimiiu.
Special thanks to our playtesters: Zanntendo, HenryV3, KleinerMuefffin, KaiChibi, Dragonod, VelvetNero, LostSoul3390, amogus, DeneralGumbass, Archer, Enchada, Herbat.

Want to hear the OST? Check out the Boombox cart!

Features

Over 10 levels of platforming action!
Two levels of difficulty, NORMAL and HARD. The latter is indeed hard, don't say we didn't warn you!
Several types of enemies, including a big, mean, [REDACTED]!
Epic 8-bit music based on the show's.
Many lines of dialog between the Rookie and his Supervisor.

autopawn [Lexaloffle Blog Feed]

Possible cart data race-condition

murder_drones_virtual_training

Controls

Credits

Features