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Lmocinemod

Alright, tooling and technical debt. Shouldn't be really much to talk aboutโ€ฆ oh, wait, this is still ReC98 :tannedcirno:

For the tooling part, I finished up the remaining ergonomics and error handling for the ๐Ÿ“ sprite converter that Jonathan Campbell contributed two months ago. While I familiarized myself with the tool, I've actually ran into some unreported errors myself, so this was sort of important to me. Still got no command-line help in there, but the error messages can now do that job probably even better, since we would have had to write them anyway.

So, what's up with the technical debt then? Well, by now we've accumulated quite a number of ๐Ÿ“ ASM code slices that need to be either decompiled or clearly marked as undecompilable. Since we define those slices as "already reverse-engineered", that decision won't affect the numbers on the front page at all. But for a complete decompilation, we'd still have to do this someday. So, rather than incorporating this work into pushes that were purchased with the expectation of measurable progress in a certain area, let's take the "anything goes" pushes, and focus entirely on that during them.

The second code segment seemed like the best place to start with this, since it affects the largest number of games simultaneously. Starting with TH02, this segment contains a set of random "core" functions needed by the binary. Image formats, sounds, input, math, it's all there in some capacity. You could maybe call it all "libzun" or something like that? But for the time being, I simply went with the obvious name, seg2. Maybe I'll come up with something more convincing in the future.


Oh, but wait, why were we assembling all the previous undecompilable ASM translation units in the 16-bit build part? By moving those to the 32-bit part, we don't even need a 16-bit TASM in our list of dependencies, as long as our build process is not fully 16-bit.
And with that, ReC98 now also builds on Windows 95, and thus, every 32-bit Windows version. ๐ŸŽ‰ Which is certainly the most user-visible improvement in all of these two pushes. :onricdennat:


Back in 2015, I already decompiled all of TH02's seg2 functions. As suggested by the Borland compiler, I tried to follow a "one translation unit per segment" layout, bundling the binary-specific contents via #include. In the end, it required two translation units โ€“ and that was even after manually inserting the original padding bytes via #pragma codestringโ€ฆ yuck. But it worked, compiled, and kept the linker's job (and, by extension, segmentation worries) to a minimum. And as long as it all matched the original binaries, it still counted as a valid reconstruction of ZUN's code. :zunpet:

However, that idea ultimately falls apart once TH03 starts mixing undecompilable ASM code inbetween C functions. Now, we officially have no choice but to use multiple C and ASM translation units, with maybe only just one or two #includes in themโ€ฆ

โ€ฆor we finally start reconstructing the actual seg2 library, turning every sequence of related functions into its own translation unit. This way, we can simply reuse the once-compiled .OBJ files for all the binaries those functions appear in, without requiring that additional layer of translation units mirroring the original segmentation.
The best example for this is TH03's almost undecompilable function that generates a lookup table for horizontally flipping 8 1bpp pixels. It's part of every binary since TH03, but only used in that game. With the previous approach, we would have had to add 9 C translation units, which would all have just #included that one file. Now, we simply put the .OBJ file into the correct place on the linker command line, as soon as we can.

๐Ÿ’ก And suddenly, the linker just inserts the correct padding bytes itself.

The most immediate gains there also happened to come from TH03. Which is also where we did get some tiny RE% and PI% gains out of this after all, by reverse-engineering some of its sprite blitting setup code. Sure, I should have done even more RE here, to also cover those 5 functions at the end of code segment #2 in TH03's MAIN.EXE that were in front of a number of library functions I already covered in this push. But let's leave that to an actual RE push ๐Ÿ˜›


All in all though, I was just getting started with this; the real gains in terms of removed ASM files are still to come. But in the meantime, the funding situation has become even better in terms of allowing me to focus on things nobody asked for. ๐Ÿ™‚ So here's a slightly better idea: Instead of spending two more pushes on this, let's shoot for TH05 MAINE.EXE position independence next. If I manage to get it done, we'll have a 100% position-independent TH05 by the time -Tom- finishes his MAIN.EXE PI demo, rather than the 94% we'd get from just MAIN.EXE. That's bound to make a much better impression on all the people who will then (re-)discover the project.