Decomp Fixup

Melee Build Fixup

You are an expert at fixing build issues in the Melee decompilation project. This skill focuses on resolving compilation errors AFTER a function has been matched to its assembly - the matching work is done, but the build is broken.

When to Use This Skill

Use /decomp-fixup when:

• A matched function causes build failures
• Headers have UNK_RET/UNK_PARAMS that need real signatures
• Callers need updates after signature changes
• Struct definitions are causing type errors
• --require-protos build is failing

Use /decomp instead when:

• You need to match assembly (get 100% match)
• You're starting fresh on a function

Finding Functions That Need Fixes

# Check state for functions that may need build fixes
melee-agent state status

# Look for functions in "committed" state that may have broken builds
# Or check functions with known issues
melee-agent state status <function_name>

Diagnosing Build Errors

Step 1: Run the Build

cd <worktree> && python configure.py --require-protos && ninja

The --require-protos flag is critical - it's what CI uses. Common error types:

Step 2: Locate the Header

Function headers are typically in:

melee/include/melee/<module>/forward.h   # Forward declarations
melee/include/melee/<module>/<file>.h    # Full declarations

Example paths:

• ft_* functions: melee/include/melee/ft/forward.h or melee/include/melee/ft/ftcommon.h
• lb* functions: melee/include/melee/lb/forward.h
• gr* functions: melee/include/melee/gr/forward.h

Step 3: Find Callers

When you change a function's signature, find and fix all callers:

grep -r "function_name" <worktree>/src/melee/
grep -r "function_name" <worktree>/include/melee/

Common Fixes

Fix 1: Header Signature Mismatch

Problem: Header has stub declaration, implementation has real signature.

// Before (in header - stub declaration):
/* 0D7268 */ UNK_RET ftCo_800D7268(UNK_PARAMS);

// After (matches implementation):
/* 0D7268 */ void ftCo_800D7268(Fighter* fp, s32 arg1);

Steps:

1. Find the implementation in src/melee/
2. Copy the exact signature
3. Update the header declaration
4. Keep the /* address */ comment if present

Fix 2: UNK_RET to Real Return Type

// Before:
UNK_RET func(s32 x);

// After (if implementation returns void):
void func(s32 x);

// After (if implementation returns a value):
s32 func(s32 x);

Note: M2C_UNK can be used as a placeholder return type when the actual type is still being determined.

Fix 3: UNK_PARAMS to Real Parameters

// Before:
void func(UNK_PARAMS);

// After (from implementation):
void func(HSD_GObj* gobj, s32 action_id, float frame);

Fix 4: Updating Callers

When a signature changes from void foo(void) to void foo(s32 arg):

// Before (caller):
foo();

// After (caller - must pass argument):
foo(0);  // Or appropriate value based on context

Finding the right argument:

• Check assembly at call sites
• Look at r3/r4/etc register values before bl instruction
• Check if there's a pattern in similar functions

Fix 5: Missing Parameter Names

Headers need parameter names for documentation, but types must match:

// Before (missing names):
void func(s32, float, HSD_GObj*);

// After (with names):
void func(s32 action, float frame, HSD_GObj* gobj);

Fix 6: Struct/Type Issues

If a struct field type is wrong:

// Workaround in code (temporary fix):
#define DMG_X1898(fp) (*(float*)&(fp)->dmg.x1898)

// Better: Fix the struct definition in the header
// Before:
s32 x1898;
// After:
float x1898;

Workflow

Quick Fix (Single Function)

# 1. Check build error
cd <worktree> && ninja 2>&1 | head -50

# 2. Find header location
grep -r "function_name" <worktree>/include/

# 3. Find implementation
grep -r "function_name" <worktree>/src/melee/

# 4. Compare signatures and fix header

# 5. Find and fix callers if signature changed
grep -r "function_name(" <worktree>/src/melee/

# 6. Rebuild and verify
ninja

Batch Fix (Multiple Issues)

# 1. Get full error list
cd <worktree> && python configure.py --require-protos && ninja 2>&1 | tee build_errors.txt

# 2. Categorize errors
grep "conflicting types" build_errors.txt
grep "implicit declaration" build_errors.txt
grep "too few arguments" build_errors.txt

# 3. Fix in dependency order (headers first, then callers)

Committing Fixes

After fixing build issues:

# Verify build passes
cd <worktree> && python configure.py --require-protos && ninja

# Commit the fix (in the worktree)
git add -A
git commit -m "Fix build: update <function> signature in header"

Commit message patterns:

• Fix build: update ftCo_800D7268 signature in header
• Fix build: add missing prototype for lbColl_80008440
• Fix build: update callers for gr_800123AB signature change

Checklist Before Committing

1. Build passes with --require-protos
2. No merge conflict markers in files
3. Header signatures match implementations exactly
4. All callers updated if signature changed
5. No UNK_RET/UNK_PARAMS left for functions you've implemented

Common Mistakes

1. Fixing implementation instead of header - If match is 100%, don't touch the .c file
2. Forgetting callers - One signature change can break many files
3. Wrong worktree - Make sure you're in the right subdirectory worktree
4. Partial fixes - Don't commit until ALL errors are resolved
5. Changing matched code - Only fix headers/callers, not the matched implementation

Type Reference

Common types in Melee:

• s8, s16, s32 - signed integers
• u8, u16, u32 - unsigned integers
• f32, f64 - floats
• BOOL - boolean (actually s32)
• HSD_GObj* - game object pointer
• Fighter* - fighter state pointer
• Vec3 - 3D vector struct
• M2C_UNK - unknown type placeholder

What NOT to Do

1. Don't modify matched code - The .c implementation is correct, fix the header
2. Don't skip --require-protos - Regular build may pass but CI will fail
3. Don't leave partial fixes - Fix everything or nothing
4. Don't guess signatures - Check the actual implementation
5. Don't ignore callers - They WILL break if signature changes

Troubleshooting