c99-migration-guide

name	c99_migration_guide
description	Master reference for migrating the GnollHack C codebase from K&R C to C99, covering conversion phases, ordering dependencies, rules for what changes and what stays, per-file workflow, verification steps, and coordination between header and source file modernization.

C99 Migration Guide

Critical Rules

• Do NOT convert system headers (e.g., amiconf.h, ntconf.h). Focus only on core game logic (src/ and core include/).
• Convert ONE file at a time. Ensure the file compiles before moving to the next.
• Do NOT combine C99 conversion with feature changes or bug fixes. This is a strict refactoring task.
• Do NOT modify function logic. Only change function signatures and variable declarations.

Migration Phases

1. Source File Conversion (src/*.c):
   • Convert K&R function definitions to C99 prototypes.
   • Expand grouped parameters (e.g., int x, y -> int x, int y).
   • Remove STATIC_DCL, STATIC_OVL, STATIC_PTR wrappers (replace with static).
   • Convert VA_DECL variadic functions (see c99_function_conversion/references/variadic_conversion.md).
   • Remove register keyword.
2. Header Modernization (include/*.h):
   • Done AFTER source files are converted.
   • Remove FDECL, NDECL, VDECL from extern.h.
   • Update parameter type macros (BOOLEAN_P to boolean, etc.).
   • Comment out compatibility macros in tradstdc.h as the final step.

Per-File Workflow

1. Select a file in src/.
2. Find all function definitions and convert K&R style to C99 ANSI style.
3. Replace STATIC_... macros with static.
4. Run the build to verify no syntax errors.
5. Commit the file.

What Stays (Do NOT change)

• const qualifiers.
• #ifdef blocks (keep both branches if both use K&R, but typically GnollHack only builds one branch; convert all visible code).
• Variable naming.
• NORETURN and PRINTF_F attributes.