Mac NET_D2GS_SERVER_Send_0x26_Chat: void __cdecl (pClient, szText) tail-call wrapper
Mac 0x001ffed5 is "undefined (void)", convention unknown. Its whole body is PUSH EBP; MOV EBP,ESP; POP EBP; JMP 0x001b1c79, a tail call that hands its own stack args unchanged to NET_D2GS_SERVER_Send_0x26_CHATSTART (void __cdecl (D2ClientStrc* pClient, char* szText)). So it takes the same two cdecl args and returns nothing. Windows twin 0x0054a5c0 is likewise a 5-byte jump with void (D2ClientStrc* pClient, <packet ptr>).
Changes 1, applied together
Set prototype
mac 0x001ffed5signatureundefined NET_D2GS_SERVER_Send_0x26_Chat(void)→void NET_D2GS_SERVER_Send_0x26_Chat(D2ClientStrc * pClient, char * szText)conventionunknown→__cdecl