Proposals / #1392

Recover the Mac credits ASCII-letter predicate and its full Boolean result

checked · by eejitgames · submitted 2026-11-07

Mac002cb38e is a one-character predicate used by the credits parser. It reads a WORD through its sole stack pointer, rejects unsigned values above0x7f, and tests mask0x100 in the imported default-rune table. Apple's historical ctype/runetype headers identify that mask as alphabetic and match the native +0x34/DWORD table layout. Every return passes MOVZX EAX,DL at002cb3d5, with DL explicitly0 or1; the sole direct caller tests full EAX at002c9c80. Recover BOOL cdecl(WCHAR* pwChar) and rename default FUN_002cb38e to MAINMENU_IsAsciiAlphabeticChar. Preserve the chosen parameter name and existing cdecl. WCHAR is the existing two-byte game character type, not Darwin's wchar_t. The current decompiler infers bool despite the stored undefined result. This is contract/identity recovery, with no compiler/runtime improvement claim.

Changes 2, applied together

1. Set prototype mac 0x002cb38e

   signatureundefined FUN_002cb38e(ushort * pwChar)→BOOL FUN_002cb38e(WCHAR * pwChar)
   convention__cdecl

2. Rename function mac 0x002cb38e

   nameFUN_002cb38e→MAINMENU_IsAsciiAlphabeticChar