ph/docs/decompiling.md

Decompiling

This document describes how you can start decompiling code and contribute to the project. Feel free to ask for help if you get stuck or need assistance.

• Decompiling a function
• The Ghidra project

Decompiling a function

Say you've found a function you want to decompile. Here are the steps we recommend for decompiling it:

1. Visit decomp.me and start decomping.
2. Under the platforms, select "Nintendo DS".
3. Select compiler version 2.0sp1p5.
4. Copy and paste the target assembly for your function, including the func_start and func_end macros, and the pool constants. For example:

	.global func_ov09_0211bf48
	thumb_func_start func_ov09_0211bf48
func_ov09_0211bf48: ; 0x0211bf48
	ldr r0, _0211bf50 ; =data_ov09_0211f59c
	ldrb r0, [r0]
	bx lr
	nop
	thumb_func_end func_ov09_0211bf48
_0211bf50: .word data_ov09_0211f59c

6. Run m2ctx.py include/MyHeader.hpp -c to generate a context and put it in your clipboard.
   • If no suitable header file exists, make a new one and put any structs and types you need in there.
7. Paste the context into decomp.me, and create the scratch.
8. Copy the CC_FLAGS from Makefile into the arguments field in decomp.me.
   • Replace the -d $(REGION) flag with whichever region you intend to decompile for. You can also delete the flag entirely if the function contains no region differences.
9. Decompile the function and try to get a 100% match.
   • There's no ARM decompiler in decomp.me yet, but Ghidra does the job quite well. See the Ghidra section for more info.
   • If you're unable to get a 100% match, share your decomp.me scratch with other contributors and they may assist you.
   • In the worst case, you can also contribute non-matching functions to this project.

The Ghidra project

We use a shared Ghidra project to analyze the game and decompile functions. We can't give access to the Ghidra server just yet, so come back here later for instructions on how to access it.