Alice Averlong🏳️⚧️> Exception while decompiling 208e:4094: Decompiler process died
this would be easier if Ghidra would STOP FUCKING CRASHING
oh god this code better not be jumping into the middle of an instruction
it's always fun to find things like that while looking at disassembly. it's a telltale sign that the compiled code ends here. a human wrote this
here there be dragons
NOPE! it just checks if you're on an even level, and then tells you to fuck off if so.
idea: what happen if I sabotage this check and make it always let you save?
it's time... for hax
75 09 ; JNZ +9
turns into
EB 09 ; JMP +9
turns into
EB 09 ; JMP +9
and it loads properly. Nothing about the level state is saved (other than your player position relative to the default camera position), mind you, so there's not really any reason to do this.
Although it does... okay I think I may have figured out why they did this. One moment while I test.
Although it does... okay I think I may have figured out why they did this. One moment while I test.
okay I think I know why they disabled mid-level saving:
so, they don't save your position or level state when saving a game, but there IS an exploit: the gun powerup
so, they don't save your position or level state when saving a game, but there IS an exploit: the gun powerup
the gun powerup is unique in that it can be collected multiple times. The game is smart enough to not let you collect permanent powerups again: if you enter the level where you get the jump boots already wearing them, they simply won't spawn
but that's not the case with the gun powerup because you collect up to three of them over the course of the game. The game doesn't know if it should make them appear or not, since you may have gotten a previous one
and if you can save mid-level, your gun powerup state is saved.
So you enter level 4, collect the gun powerup, and save. quit and restore your game. You now have the gun powerup, and you can collect it again, getting you to gun level 3. Save and restore again, and now you're max gun level (4).
So you enter level 4, collect the gun powerup, and save. quit and restore your game. You now have the gun powerup, and you can collect it again, getting you to gun level 3. Save and restore again, and now you're max gun level (4).
and making you save only in hallways avoids this. And the game stores the state of duke in the last hallway: so when you use f10 to restart, it takes you back to the last hallway, but you lose all your upgrades
so you can't use this trick.
now I think they could have solved this in another way: make the save function save the state of duke as he entered the level. They already save that for restoring the player when you die
but maybe they didn't figure out this exploit into late in development and just sticking a "you can only save in hallways" patch on it was easier
you can also use this trick to get infinite health, but that's a much less impactful exploit than maxing out your gun much earlier
oh interesting.
the game does reuse a dialog box!
just one of them: The main-hallway hints and Dr. Proton's security-camera taunts? They're literally the same system, with the two sets of text intertwined.
the game selects what message to play based on your current level. on odd-numbered levels, it ends up being a hint message (because those are the hallway levels), and on even-numbered levels, it's dr. proton taunting you
my ghidra is full of a lot of comments like "this actually points to keyboard_interrupt_handler" because ghidra is mis-compiling this so badly
ghidra really doesn't do a great job of handling 32bit pointers in a 16bit real mode program.
The problem is that they're handled as two 16bit integers, not a single 32bit integer.
The problem is that they're handled as two 16bit integers, not a single 32bit integer.
So sometimes a function fill be like void foobar(int a, int b, char far * string)
and ghidra will be like "oh it takes 4 parameters!"
nope! far pointers are passed as two 16-bit integers but actually represent one 20/24-bit pointer.
honestly real mode x86 is such an abomination of nonsense that we should pretend it doesn't exist.
if only for the minor problem that nearly all PC software and games were written in it for like 12 years
ugh. I don't know what this function even does but I can already tell that the only difference between two adjacent functions is which pointers they use.
TODD, PARAMETERS. PARAMETERS TODD
I'm really doubting the function duplications has anything to do with aggressive compiler optimizations because there's one very small function to determine if something is onscreen or not. It's a couple additions and 4 compares. prime inlining material!
it's not inlined. it's far-called from 148 locations
optimization level: this is a consumer-grade compiler for DOS from 1988, you're lucky we even know what optimization is
I hope this is just me misunderstanding the purpose of this function and this game doesn't just have a function named process_sodas
oh fuck me I think it does
instead of having a big array called like GameObjects and a big update function that loops through them all, I think there's separate arrays for sodas and turkeys and atomic molecules and flags and footballs and floppy disks and and and
and a separate copy-pasted function to update each one
I'm going to set this game on fire
oh god it even does it for static things like doors
apparently every frame it loops through the doors array and checks if the player is standing in front of them and then checks if the player is pushing the up key
instead of, you know, waiting until the user pushes the up key, then figuring out what they're in front of, and triggering the appropriate action
also apparently beating the game gives you 34,464 points.
random-ass number.
random-ass number.
at least it doesn't loop over a shoes array, since there can only be one per level
I'm now doing some hybrid static/dynamic debugging. I set a breakpoint on the add_score function, then I'm doing stuff to get points, and seeing what function called add_score
there's a separate function and array that's looped over for EVERY SINGLE ENEMY TYPE
my current theory:
todd replogle didn't really understand C programming but unfortunately did a lot of it when he made duke nukem 1
todd replogle didn't really understand C programming but unfortunately did a lot of it when he made duke nukem 1
Niko (lethal_guitar)@foone he made quite a leap with Cosmo and Duke 2. But still often preferred global variables over function parameters, for some reason.