<div dir="ltr">Hello, I'm trying out PLT Scheme FFI on WIn32. Examples included into the distribution show only simpler cases. Here is the C snippet I'm trying to translate: typedef unsigned char BYTE; typedef BYTE* LPBYTE; typedef const BYTE* LPCBYTE; typedef unsigned long DWORD; typedef DWORD* LPDWORD; typedef void* SCARDHANDLE; // Just an handle. typedef struct _SCARD_IO_REQUEST{     DWORD dwProtocol;   // Protocol identifier     DWORD cbPciLength;  // Protocol Control Information Length <div id="qhide_87640" style="display: block; font-family: courier new,monospace;" class="qt"> } SCARD_IO_REQUEST, *PSCARD_IO_REQUEST, *LPSCARD_IO_REQUEST;   </div>typedef const SCARD_IO_REQUEST *LPCSCARD_IO_REQUEST; LONG SCardTransmit(   /* IN */  SCARDHANDLE hCard,   /* IN */  LPCSCARD_I0_REQUEST pioSendPci,   /* IN */  LPCBYTE pbSendBuffer,   /* IN */  DWORD cbSendLength,   /* OUT */ LPSCARD_IO_REQUEST pioRecvPci,   /* OUT */ LPBYTE pbRecvBuffer,   /* OUT */ LPDWORD pcbRecvLength ); Here the resulting PLT Scheme code, with compiler errors: (module winscard mzscheme   (require mzlib/foreign)   (unsafe!)   (define _DWORD _int) ;; It should be 32 bits unsigned integer.   (define _LONG _int) ;; OK: 32 bits integer.   (define _SCARDHANDLE _int) ;; This is an handle, I'd prefer using a "typed" integer for type checking.   (define-cstruct _SCARD_IO_REQUEST ((dwProtocol _DWORD) ;;   // Protocol identifier                                      (cbPciLength _DWORD))) ;;  // Protocol Control Information Length   (define winscard (ffi-lib "winscard"))    ;; [simpler functions not included]   (provide scard-transmit)   (define-struct scard-transmit-result (error recv-pci recv-buffer recv-length))   (define scard-transmit (get-ffi-obj "SCardTransmit" winscard       (_fun (hCard : _SCARDHANDLE)             (pioSendPci : _SCARD_I0_REQUEST-pointer) ;; ERROR: expand: unbound variable in module in: __SCARD_I0_REQUEST-pointer             (pbSendBuffer : (_cvector i _byte)) ;; ERROR: expand: unbound variable in module in: i             (cbSendLength : _DWORD)             (ioRecvPci : (_ptr o _SCARD_IO_REQUEST))             (pbRecvBuffer :  (_cvector o _byte )) ;; ERROR: expand: unbound variable in module in: o             (cbRecvLength : (_ptr o _DWORD))             -> (error : _LONG)             -> (make-scard-transmit-result error ioRecvPci pbRecvBuffer cbRecvLength)))) ) What's wrong? And what about byte aligned, word aligned, double word aligned  structures? What about calling conventions? Thanks </div>