Fix COMM.DRV calling conventions and add ComDEB compatibility

Resolve GPFs in both USER.EXE and COMMTASK.DLL by correcting RETF
sizes for SETCOM and GETDCB, confirmed by disassembling CyberCom.DRV.
Add stock-compatible ComDEB structure so third-party code (ProComm
COMMTASK.DLL) can safely access internal fields at known offsets per
Microsoft KB Q101417.

COMM.DRV changes:
- SETCOM (ord 2): RETF 4, takes DCB FAR * only (not commId + DCB*)
- GETDCB (ord 15): RETF 2, takes commId, returns DCB FAR * in DX:AX
- Add 40-byte ComDebT matching stock COMM.DRV internal layout
  (evtWord at +0, MSR shadow at +35, queue counts at +8/+18)
- cevt returns pointer to ComDebT for third-party compatibility
- Sync ComDEB fields in ISR dispatch, reccom, sndcom, cflush, setque
- Move WEP to ordinal 16, add ordinal 101 stub (match stock/CyberCom)
- Default DBG_ENABLED to 0 (set to 1 to re-enable debug logging)

VBX control fixes:
- Fix SETBREAK/CLRBREAK constants (use numeric 8/9, not undefined macros)
- Fix serialEnableNotify return type (BOOL, not int16_t)
- Fix mscomm.h to work with RC compiler (#ifndef RC_INVOKED)
- Fix vbapi.h USHORT typedef and MODEL.flWndStyle type
- Add vbapi.lib dependency to makefile

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

drv/commdrv.c

@@ -10,12 +10,154 @@
 #include <dos.h>
 #include <string.h>
 
+// -----------------------------------------------------------------------
+// Debug logging via OutputDebugString
+// -----------------------------------------------------------------------
+#define DBG_ENABLED 0
+
+#if DBG_ENABLED
+static void dbgStr(const char FAR *msg)
+{
+    OutputDebugString(msg);
+}
+
+// Log a label and a 16-bit hex value: "label: 0xNNNN\r\n"
+static void dbgHex16(const char FAR *label, uint16_t val)
+{
+    static const char hex[] = "0123456789ABCDEF";
+    char buf[48];
+    int  i;
+
+    for (i = 0; i < 40 && label[i]; i++) {
+        buf[i] = label[i];
+    }
+    buf[i++] = ':';
+    buf[i++] = ' ';
+    buf[i++] = '0';
+    buf[i++] = 'x';
+    buf[i++] = hex[(val >> 12) & 0xF];
+    buf[i++] = hex[(val >> 8) & 0xF];
+    buf[i++] = hex[(val >> 4) & 0xF];
+    buf[i++] = hex[val & 0xF];
+    buf[i++] = '\r';
+    buf[i++] = '\n';
+    buf[i]   = '\0';
+    OutputDebugString(buf);
+}
+
+// Log a label and a signed 16-bit value: "label: -NNNN\r\n"
+static void dbgInt16(const char FAR *label, int16_t val)
+{
+    char     buf[48];
+    int      i;
+    uint16_t uv;
+
+    for (i = 0; i < 40 && label[i]; i++) {
+        buf[i] = label[i];
+    }
+    buf[i++] = ':';
+    buf[i++] = ' ';
+
+    if (val < 0) {
+        buf[i++] = '-';
+        uv = (uint16_t)(-(int)val);
+    } else {
+        uv = (uint16_t)val;
+    }
+
+    // Print decimal (up to 5 digits)
+    {
+        char digits[6];
+        int  n = 0;
+        do {
+            digits[n++] = (char)('0' + (uv % 10));
+            uv /= 10;
+        } while (uv > 0);
+        while (n > 0) {
+            buf[i++] = digits[--n];
+        }
+    }
+
+    buf[i++] = '\r';
+    buf[i++] = '\n';
+    buf[i]   = '\0';
+    OutputDebugString(buf);
+}
+
+// Log a FAR pointer as "label: SSSS:OOOO\r\n"
+static void dbgFarPtr(const char FAR *label, void FAR *ptr)
+{
+    static const char hex[] = "0123456789ABCDEF";
+    char     buf[48];
+    int      i;
+    uint16_t seg;
+    uint16_t off;
+
+    seg = _FP_SEG(ptr);
+    off = _FP_OFF(ptr);
+
+    for (i = 0; i < 32 && label[i]; i++) {
+        buf[i] = label[i];
+    }
+    buf[i++] = ':';
+    buf[i++] = ' ';
+    buf[i++] = hex[(seg >> 12) & 0xF];
+    buf[i++] = hex[(seg >> 8) & 0xF];
+    buf[i++] = hex[(seg >> 4) & 0xF];
+    buf[i++] = hex[seg & 0xF];
+    buf[i++] = ':';
+    buf[i++] = hex[(off >> 12) & 0xF];
+    buf[i++] = hex[(off >> 8) & 0xF];
+    buf[i++] = hex[(off >> 4) & 0xF];
+    buf[i++] = hex[off & 0xF];
+    buf[i++] = '\r';
+    buf[i++] = '\n';
+    buf[i]   = '\0';
+    OutputDebugString(buf);
+}
+
+// Hex dump first 'count' bytes at a FAR pointer
+static void dbgDump(const char FAR *label, void FAR *ptr, int count)
+{
+    static const char hex[] = "0123456789ABCDEF";
+    char              buf[80];
+    uint8_t FAR      *p;
+    int               i;
+    int               bi;
+
+    p = (uint8_t FAR *)ptr;
+
+    // Print label
+    for (bi = 0; bi < 32 && label[bi]; bi++) {
+        buf[bi] = label[bi];
+    }
+    buf[bi++] = ':';
+    buf[bi++] = ' ';
+
+    for (i = 0; i < count && bi < 70; i++) {
+        buf[bi++] = hex[(p[i] >> 4) & 0xF];
+        buf[bi++] = hex[p[i] & 0xF];
+        buf[bi++] = ' ';
+    }
+    buf[bi++] = '\r';
+    buf[bi++] = '\n';
+    buf[bi]   = '\0';
+    OutputDebugString(buf);
+}
+#else
+#define dbgStr(msg)          ((void)0)
+#define dbgHex16(label, val) ((void)0)
+#define dbgInt16(label, val) ((void)0)
+#define dbgFarPtr(label, p)  ((void)0)
+#define dbgDump(l, p, n)     ((void)0)
+#endif
+
 // -----------------------------------------------------------------------
 // Prototypes
 // -----------------------------------------------------------------------
-int16_t FAR PASCAL _export inicom(DCB FAR *dcb, char FAR *rxBuf, int16_t rxSize);
+int16_t FAR PASCAL _export inicom(DCB FAR *dcb);
 int16_t FAR PASCAL _export setcom(DCB FAR *dcb);
-int16_t FAR PASCAL _export setque(int16_t commId, char FAR *rxBuf, int16_t rxSize, char FAR *txBuf, int16_t txSize);
+int16_t FAR PASCAL _export setque(int16_t commId, int16_t rxSize, int16_t txSize);
 int16_t FAR PASCAL _export reccom(int16_t commId, void FAR *buf, int16_t len);
 int16_t FAR PASCAL _export sndcom(int16_t commId, void FAR *buf, int16_t len);
 int16_t FAR PASCAL _export ctx(int16_t commId, int16_t ch);
@@ -27,13 +169,14 @@ int16_t FAR PASCAL _export cextfcn(int16_t commId, int16_t func);
 int16_t FAR PASCAL _export cflush(int16_t commId, int16_t queue);
 int16_t FAR PASCAL _export csetbrk(int16_t commId);
 int16_t FAR PASCAL _export cclrbrk(int16_t commId);
-int16_t FAR PASCAL _export getdcb(int16_t commId, DCB FAR *dcb);
+DCB FAR * FAR PASCAL _export getdcb(int16_t commId);
 void    FAR PASCAL _export suspendOpenCommPorts(void);
 void    FAR PASCAL _export reactivateOpenCommPorts(void);
 int16_t FAR PASCAL _export commWriteString(int16_t commId, void FAR *buf, int16_t len);
 int16_t FAR PASCAL _export readCommString(int16_t commId, void FAR *buf, int16_t len);
 int16_t FAR PASCAL _export enableNotification(int16_t commId, HWND hwnd, int16_t rxThresh, int16_t txThresh);
 
+int     FAR PASCAL _export commNotifyWndProc(void);
 int     FAR PASCAL LibMain(HANDLE hInstance, WORD wDataSeg, WORD wHeapSize, LPSTR lpCmdLine);
 int     FAR PASCAL _export WEP(int nParam);
 
@@ -46,7 +189,7 @@ static int16_t  freeBuffers(PortStateT *port);
 static int16_t  initBuffers(PortStateT *port, uint16_t rxSz, uint16_t txSz);
 static void     initPortState(PortStateT *port, int16_t commId);
 void            primeTx(PortStateT *port);
-static void     readPortConfig(int16_t commId, uint16_t *baseAddr, uint8_t *irq);
+static void     readPortConfig(int16_t commId, uint16_t FAR *baseAddr, uint8_t FAR *irq);
 static uint16_t readSystemIni(const char FAR *section, const char FAR *key, uint16_t defVal);
 
 // -----------------------------------------------------------------------
@@ -70,6 +213,18 @@ PortStateT ports[MAX_PORTS];
 // -----------------------------------------------------------------------
 static HANDLE ghInstance = NULL;
 
+// -----------------------------------------------------------------------
+// Dynamically resolved PostMessage
+//
+// comm.drv is loaded from [boot] before USER.EXE, so we can't have a
+// static import for PostMessage. Resolve it on first use via
+// GetProcAddress(GetModuleHandle("USER"), "PostMessage").
+// -----------------------------------------------------------------------
+PostMessageProcT pfnPostMessage = NULL;
+
+// ISR hit counter for diagnostics
+volatile uint16_t isrHitCount = 0;
+
 
 // -----------------------------------------------------------------------
 // applyBaudRate - Set the baud rate divisor on the UART
@@ -215,6 +370,8 @@ int16_t FAR PASCAL _export cclrbrk(int16_t commId)
     PortStateT *port;
     uint8_t     lcr;
 
+    dbgInt16("COMM.DRV: cclrbrk Id", commId);
+
     if (commId < 0 || commId >= MAX_PORTS) {
         return -1;
     }
@@ -243,6 +400,22 @@ int32_t FAR PASCAL _export cevt(int16_t commId, int16_t evtMask)
 {
     PortStateT *port;
     uint16_t FAR *ptr;
+    int32_t       retVal;
+
+#if DBG_ENABLED
+    {
+        uint16_t ssSeg;
+        uint16_t bpVal;
+        _asm mov ssSeg, ss
+        _asm mov bpVal, bp
+        dbgHex16("COMM.DRV: cevt SS", ssSeg);
+        dbgHex16("COMM.DRV: cevt BP", bpVal);
+        dbgDump("COMM.DRV: cevt stk", (void FAR *)((uint32_t)ssSeg << 16 | (bpVal + 6)), 16);
+    }
+#endif
+
+    dbgInt16("COMM.DRV: cevt Id", commId);
+    dbgHex16("COMM.DRV: cevt mask", (uint16_t)evtMask);
 
     if (commId < 0 || commId >= MAX_PORTS) {
         return 0L;
@@ -250,13 +423,18 @@ int32_t FAR PASCAL _export cevt(int16_t commId, int16_t evtMask)
 
     port = &ports[commId];
     if (!port->isOpen) {
+        dbgStr("COMM.DRV: cevt not open\r\n");
         return 0L;
     }
 
-    port->evtMask = (uint16_t)evtMask;
+    port->comDeb.evtMask = (uint16_t)evtMask;
 
-    ptr = &port->evtWord;
+    ptr = &port->comDeb.evtWord;
-    return (int32_t)(void FAR *)ptr;
+    retVal = (int32_t)(void FAR *)ptr;
+    dbgHex16("COMM.DRV: cevt retSeg", (uint16_t)(retVal >> 16));
+    dbgHex16("COMM.DRV: cevt retOff", (uint16_t)(retVal & 0xFFFF));
+    dbgStr("COMM.DRV: cevt OK\r\n");
+    return retVal;
 }
 
 
@@ -270,6 +448,8 @@ uint16_t FAR PASCAL _export cevtget(int16_t commId, int16_t evtMask)
     PortStateT *port;
     uint16_t    events;
 
+    dbgInt16("COMM.DRV: cevtget Id", commId);
+
     if (commId < 0 || commId >= MAX_PORTS) {
         return 0;
     }
@@ -280,8 +460,8 @@ uint16_t FAR PASCAL _export cevtget(int16_t commId, int16_t evtMask)
     }
 
     _disable();
-    events = port->evtWord & (uint16_t)evtMask;
+    events = port->comDeb.evtWord & (uint16_t)evtMask;
-    port->evtWord &= ~(uint16_t)evtMask;
+    port->comDeb.evtWord &= ~(uint16_t)evtMask;
     _enable();
 
     return events;
@@ -299,6 +479,9 @@ int16_t FAR PASCAL _export cextfcn(int16_t commId, int16_t func)
     uint8_t     mcr;
     uint16_t    base;
 
+    dbgInt16("COMM.DRV: cextfcn Id", commId);
+    dbgInt16("COMM.DRV: cextfcn func", func);
+
     if (commId < 0 || commId >= MAX_PORTS) {
         return -1;
     }
@@ -328,9 +511,9 @@ int16_t FAR PASCAL _export cextfcn(int16_t commId, int16_t func)
             mcr &= ~MCR_RTS;
             port->rtsState = FALSE;
             break;
-        case SETBREAK:
+        case ESC_SETBREAK:
             return csetbrk(commId);
-        case CLRBREAK:
+        case ESC_CLRBREAK:
             return cclrbrk(commId);
         case RESETDEV:
             // No-op for serial ports
@@ -364,6 +547,8 @@ int16_t FAR PASCAL _export cflush(int16_t commId, int16_t queue)
 {
     PortStateT *port;
 
+    dbgInt16("COMM.DRV: cflush Id", commId);
+
     if (commId < 0 || commId >= MAX_PORTS) {
         return -1;
     }
@@ -378,6 +563,9 @@ int16_t FAR PASCAL _export cflush(int16_t commId, int16_t queue)
         port->rxHead  = 0;
         port->rxTail  = 0;
         port->rxCount = 0;
+        port->comDeb.qInHead  = 0;
+        port->comDeb.qInTail  = 0;
+        port->comDeb.qInCount = 0;
         // Reset FIFO to clear hardware buffer too
         if (port->is16550 && port->fifoEnabled) {
             _outp(port->baseAddr + UART_FCR, FCR_ENABLE | FCR_RX_RESET | port->fifoTrigger);
@@ -386,6 +574,9 @@ int16_t FAR PASCAL _export cflush(int16_t commId, int16_t queue)
         port->txHead  = 0;
         port->txTail  = 0;
         port->txCount = 0;
+        port->comDeb.qOutHead  = 0;
+        port->comDeb.qOutTail  = 0;
+        port->comDeb.qOutCount = 0;
         if (port->is16550 && port->fifoEnabled) {
             _outp(port->baseAddr + UART_FCR, FCR_ENABLE | FCR_TX_RESET | port->fifoTrigger);
         }
@@ -401,10 +592,26 @@ int16_t FAR PASCAL _export cflush(int16_t commId, int16_t queue)
 // -----------------------------------------------------------------------
 int16_t FAR PASCAL _export commWriteString(int16_t commId, void FAR *buf, int16_t len)
 {
+    dbgInt16("COMM.DRV: commWriteStr Id", commId);
     return sndcom(commId, buf, len);
 }
 
 
+// -----------------------------------------------------------------------
+// commNotifyWndProc - Ordinal 101 stub (undocumented, Win 3.1 compat)
+//
+// The stock COMM.DRV and CyberCom export an unnamed function at ordinal
+// 101.  Purpose is undocumented; may be an internal callback used by
+// USER.EXE.  CyberCom's implementation uses plain RETF (no params).
+// Return 0 (not handled).
+// -----------------------------------------------------------------------
+int FAR PASCAL _export commNotifyWndProc(void)
+{
+    dbgStr("COMM.DRV: ord101 called\r\n");
+    return 0;
+}
+
+
 // -----------------------------------------------------------------------
 // csetbrk - Assert break signal (ordinal 13)
 // -----------------------------------------------------------------------
@@ -413,6 +620,8 @@ int16_t FAR PASCAL _export csetbrk(int16_t commId)
     PortStateT *port;
     uint8_t     lcr;
 
+    dbgInt16("COMM.DRV: csetbrk Id", commId);
+
     if (commId < 0 || commId >= MAX_PORTS) {
         return -1;
     }
@@ -437,6 +646,8 @@ int16_t FAR PASCAL _export ctx(int16_t commId, int16_t ch)
 {
     PortStateT *port;
 
+    dbgInt16("COMM.DRV: ctx Id", commId);
+
     if (commId < 0 || commId >= MAX_PORTS) {
         return -1;
     }
@@ -504,19 +715,35 @@ int16_t FAR PASCAL _export enableNotification(int16_t commId, HWND hwnd, int16_t
 {
     PortStateT *port;
 
+    dbgInt16("COMM.DRV: enableNotif Id", commId);
+    dbgHex16("COMM.DRV: enableNotif hwnd", (uint16_t)hwnd);
+    dbgInt16("COMM.DRV: enableNotif rxTh", rxThresh);
+    dbgInt16("COMM.DRV: enableNotif txTh", txThresh);
+
     if (commId < 0 || commId >= MAX_PORTS) {
         return FALSE;
     }
 
     port = &ports[commId];
     if (!port->isOpen) {
+        dbgStr("COMM.DRV: enableNotif not open\r\n");
         return FALSE;
     }
 
+    // Lazily resolve PostMessage from USER.EXE
+    // (not available at boot when comm.drv is loaded from [boot])
+    if (!pfnPostMessage) {
+        HMODULE hUser = GetModuleHandle("USER");
+        if (hUser) {
+            pfnPostMessage = (PostMessageProcT)GetProcAddress(hUser, "PostMessage");
+        }
+    }
+
     port->hwndNotify     = hwnd;
     port->rxNotifyThresh = rxThresh;
     port->txNotifyThresh = txThresh;
 
+    dbgStr("COMM.DRV: enableNotif OK\r\n");
     return TRUE;
 }
 
@@ -551,23 +778,32 @@ static int16_t freeBuffers(PortStateT *port)
 
 
 // -----------------------------------------------------------------------
-// getdcb - Copy current DCB settings (ordinal 15)
+// getdcb - Return pointer to internal DCB (ordinal 15)
+//
+// Takes int16_t commId (2 bytes, RETF 2).  Returns DCB FAR * in DX:AX.
+// The caller (USER.EXE / COMMTASK.DLL) copies from this pointer.
+// CyberCom confirms: RETF 2, return pointer.
 // -----------------------------------------------------------------------
-int16_t FAR PASCAL _export getdcb(int16_t commId, DCB FAR *dcb)
+DCB FAR * FAR PASCAL _export getdcb(int16_t commId)
 {
     PortStateT *port;
 
+    dbgInt16("COMM.DRV: getdcb Id", commId);
+
     if (commId < 0 || commId >= MAX_PORTS) {
-        return -1;
+        dbgStr("COMM.DRV: getdcb bad id\r\n");
+        return NULL;
     }
 
     port = &ports[commId];
     if (!port->isOpen) {
-        return -1;
+        dbgStr("COMM.DRV: getdcb not open\r\n");
+        return NULL;
     }
 
-    _fmemcpy(dcb, &port->dcb, sizeof(DCB));
+    dbgHex16("COMM.DRV: getdcb isrHits", isrHitCount);
-    return 0;
+    dbgStr("COMM.DRV: getdcb OK\r\n");
+    return &port->dcb;
 }
 
 
@@ -581,7 +817,7 @@ int16_t FAR PASCAL _export getdcb(int16_t commId, DCB FAR *dcb)
 //
 // Returns commId (0-3) on success, negative error code on failure.
 // -----------------------------------------------------------------------
-int16_t FAR PASCAL _export inicom(DCB FAR *dcb, char FAR *rxBuf, int16_t rxSize)
+int16_t FAR PASCAL _export inicom(DCB FAR *dcb)
 {
     int16_t     commId;
     PortStateT *port;
@@ -589,25 +825,52 @@ int16_t FAR PASCAL _export inicom(DCB FAR *dcb, char FAR *rxBuf, int16_t rxSize)
     uint16_t    txBufSize;
     uint8_t     mcr;
 
-    (void)rxBuf;
+    dbgStr("COMM.DRV: inicom enter\r\n");
-    (void)rxSize;
+
+    // Dump raw stack to see actual parameters passed by caller
+    {
+        uint16_t bpVal;
+        uint16_t ssVal;
+        void FAR *stkPtr;
+        _asm mov bpVal, bp
+        _asm mov ssVal, ss
+        stkPtr = (void FAR *)((uint32_t)ssVal << 16 | (bpVal + 6));
+        dbgHex16("COMM.DRV: inicom SS", ssVal);
+        dbgHex16("COMM.DRV: inicom BP", bpVal);
+        dbgDump("COMM.DRV: inicom stk", stkPtr, 24);
+    }
 
     if (!dcb) {
+        dbgStr("COMM.DRV: inicom NULL dcb\r\n");
         return IE_DEFAULT;
     }
 
+    dbgFarPtr("COMM.DRV: inicom dcb", (void FAR *)dcb);
+    dbgDump("COMM.DRV: inicom raw", (void FAR *)dcb, 16);
+    dbgHex16("COMM.DRV: sizeof(DCB)", (uint16_t)sizeof(DCB));
+
     commId = dcb->Id;
+    dbgInt16("COMM.DRV: inicom Id", commId);
+    dbgHex16("COMM.DRV: inicom BaudRate", dcb->BaudRate);
+    dbgHex16("COMM.DRV: inicom ByteSize", (uint16_t)dcb->ByteSize);
+    dbgHex16("COMM.DRV: inicom Parity", (uint16_t)dcb->Parity);
+    dbgHex16("COMM.DRV: inicom StopBits", (uint16_t)dcb->StopBits);
+
     if (commId < 0 || commId >= MAX_PORTS) {
+        dbgStr("COMM.DRV: inicom IE_BADID\r\n");
         return IE_BADID;
     }
 
     port = &ports[commId];
     if (port->isOpen) {
+        dbgStr("COMM.DRV: inicom IE_OPEN\r\n");
         return IE_OPEN;
     }
 
     // Initialize port state
     initPortState(port, commId);
+    dbgHex16("COMM.DRV: inicom baseAddr", port->baseAddr);
+    dbgHex16("COMM.DRV: inicom irq", (uint16_t)port->irq);
 
     // Read buffer sizes from SYSTEM.INI if available (COMnBuffer key)
     {
@@ -626,20 +889,26 @@ int16_t FAR PASCAL _export inicom(DCB FAR *dcb, char FAR *rxBuf, int16_t rxSize)
         rxBufSize = readSystemIni("386Enh", bufKey, DEFAULT_RX_SIZE);
     }
     txBufSize = rxBufSize;
+    dbgHex16("COMM.DRV: inicom rxBufSize", rxBufSize);
 
     // Allocate ring buffers
     if (initBuffers(port, rxBufSize, txBufSize) != 0) {
+        dbgStr("COMM.DRV: inicom IE_MEMORY\r\n");
         return IE_MEMORY;
     }
+    dbgStr("COMM.DRV: inicom buffers OK\r\n");
 
     // Detect 16550 FIFO
     port->is16550 = (uint8_t)detect16550(port->baseAddr);
+    dbgHex16("COMM.DRV: inicom is16550", (uint16_t)port->is16550);
 
     // Hook ISR
     if (hookIsr(port) != 0) {
+        dbgStr("COMM.DRV: inicom hookIsr FAIL\r\n");
         freeBuffers(port);
         return IE_HARDWARE;
     }
+    dbgStr("COMM.DRV: inicom ISR hooked\r\n");
 
     port->isOpen = TRUE;
 
@@ -675,12 +944,19 @@ int16_t FAR PASCAL _export inicom(DCB FAR *dcb, char FAR *rxBuf, int16_t rxSize)
 
     // Clear any pending status
     _inp(port->baseAddr + UART_LSR);
-    _inp(port->baseAddr + UART_MSR);
+    port->comDeb.msrShadow = (uint8_t)_inp(port->baseAddr + UART_MSR);
     _inp(port->baseAddr + UART_RBR);
 
+    // Populate ComDEB for third-party compatibility
+    port->comDeb.port      = port->baseAddr;
+    port->comDeb.baudRate   = port->baudRate;
+    port->comDeb.qInSize    = port->rxSize;
+    port->comDeb.qOutSize   = port->txSize;
+
     // Enable receive and line status interrupts
     _outp(port->baseAddr + UART_IER, IER_RDA | IER_LSI | IER_MSI);
 
+    dbgInt16("COMM.DRV: inicom OK, ret", commId);
     return commId;
 }
 
@@ -833,6 +1109,8 @@ void FAR PASCAL _export reactivateOpenCommPorts(void)
     PortStateT *port;
     uint8_t     mcr;
 
+    dbgStr("COMM.DRV: reactivate\r\n");
+
     for (i = 0; i < MAX_PORTS; i++) {
         port = &ports[i];
         if (!port->isOpen) {
@@ -873,6 +1151,7 @@ void FAR PASCAL _export reactivateOpenCommPorts(void)
 // -----------------------------------------------------------------------
 int16_t FAR PASCAL _export readCommString(int16_t commId, void FAR *buf, int16_t len)
 {
+    dbgInt16("COMM.DRV: readCommStr Id", commId);
     return reccom(commId, buf, len);
 }
 
@@ -883,7 +1162,7 @@ int16_t FAR PASCAL _export readCommString(int16_t commId, void FAR *buf, int16_t
 // Checks [386Enh] for COMnBase (hex) and COMnIRQ overrides.
 // Falls back to standard defaults if not present.
 // -----------------------------------------------------------------------
-static void readPortConfig(int16_t commId, uint16_t *baseAddr, uint8_t *irq)
+static void readPortConfig(int16_t commId, uint16_t FAR *baseAddr, uint8_t FAR *irq)
 {
     char key[10];
     char buf[16];
@@ -963,6 +1242,8 @@ int16_t FAR PASCAL _export reccom(int16_t commId, void FAR *buf, int16_t len)
     uint8_t FAR *dst;
     int16_t      bytesRead;
 
+    dbgInt16("COMM.DRV: reccom Id", commId);
+
     if (commId < 0 || commId >= MAX_PORTS) {
         return -1;
     }
@@ -1002,29 +1283,47 @@ int16_t FAR PASCAL _export reccom(int16_t commId, void FAR *buf, int16_t len)
         _enable();
     }
 
+    // Sync ComDEB queue counts
+    port->comDeb.qInCount = port->rxCount;
+    port->comDeb.qInTail  = port->rxTail;
+
     return bytesRead;
 }
 
 
 // -----------------------------------------------------------------------
 // setcom - Apply DCB settings to hardware (ordinal 2)
+//
+// Takes DCB FAR * (4 bytes, RETF 4).  CommId is in dcb->Id.
+// Both USER.EXE and COMMTASK.DLL push 4 bytes for this call.
 // -----------------------------------------------------------------------
 int16_t FAR PASCAL _export setcom(DCB FAR *dcb)
 {
     int16_t     commId;
     PortStateT *port;
 
+    dbgStr("COMM.DRV: setcom enter\r\n");
+
     if (!dcb) {
+        dbgStr("COMM.DRV: setcom NULL dcb\r\n");
         return -1;
     }
 
     commId = dcb->Id;
+    dbgInt16("COMM.DRV: setcom Id", commId);
+    dbgHex16("COMM.DRV: setcom BaudRate", dcb->BaudRate);
+    dbgHex16("COMM.DRV: setcom ByteSize", (uint16_t)dcb->ByteSize);
+    dbgHex16("COMM.DRV: setcom Parity", (uint16_t)dcb->Parity);
+    dbgHex16("COMM.DRV: setcom StopBits", (uint16_t)dcb->StopBits);
+
     if (commId < 0 || commId >= MAX_PORTS) {
+        dbgStr("COMM.DRV: setcom IE_BADID\r\n");
         return IE_BADID;
     }
 
     port = &ports[commId];
     if (!port->isOpen) {
+        dbgStr("COMM.DRV: setcom port not open\r\n");
         return -1;
     }
 
@@ -1053,8 +1352,14 @@ int16_t FAR PASCAL _export setcom(DCB FAR *dcb)
     port->xonLim   = dcb->XonLim;
     port->xoffLim  = dcb->XoffLim;
 
+    // Sync ComDEB shadow fields
+    port->comDeb.baudRate  = port->baudRate;
+    port->comDeb.lcrShadow = (uint8_t)_inp(port->baseAddr + UART_LCR);
+    port->comDeb.mcrShadow = (uint8_t)_inp(port->baseAddr + UART_MCR);
+
     _enable();
 
+    dbgStr("COMM.DRV: setcom OK\r\n");
     return 0;
 }
 
@@ -1062,22 +1367,25 @@ int16_t FAR PASCAL _export setcom(DCB FAR *dcb)
 // -----------------------------------------------------------------------
 // setque - Resize RX/TX buffers (ordinal 3)
 //
-// The stock driver ignores the buffer pointers passed by the caller
+// Caller passes port ID and requested RX/TX buffer sizes.
-// and manages its own. We do the same: free old buffers, alloc new.
+// We manage our own GlobalAlloc'd buffers.
 // -----------------------------------------------------------------------
-int16_t FAR PASCAL _export setque(int16_t commId, char FAR *rxBufArg, int16_t rxSz, char FAR *txBufArg, int16_t txSz)
+int16_t FAR PASCAL _export setque(int16_t commId, int16_t rxSz, int16_t txSz)
 {
     PortStateT *port;
 
-    (void)rxBufArg;
+    dbgInt16("COMM.DRV: setque Id", commId);
-    (void)txBufArg;
+    dbgInt16("COMM.DRV: setque rxSz", rxSz);
+    dbgInt16("COMM.DRV: setque txSz", txSz);
 
     if (commId < 0 || commId >= MAX_PORTS) {
+        dbgStr("COMM.DRV: setque bad id\r\n");
         return -1;
     }
 
     port = &ports[commId];
     if (!port->isOpen) {
+        dbgStr("COMM.DRV: setque port not open\r\n");
         return -1;
     }
 
@@ -1085,10 +1393,21 @@ int16_t FAR PASCAL _export setque(int16_t commId, char FAR *rxBufArg, int16_t rx
     freeBuffers(port);
     if (initBuffers(port, (uint16_t)rxSz, (uint16_t)txSz) != 0) {
         _enable();
+        dbgStr("COMM.DRV: setque IE_MEMORY\r\n");
         return IE_MEMORY;
     }
+    // Sync ComDEB queue sizes
+    port->comDeb.qInSize   = port->rxSize;
+    port->comDeb.qInCount  = 0;
+    port->comDeb.qInHead   = 0;
+    port->comDeb.qInTail   = 0;
+    port->comDeb.qOutSize  = port->txSize;
+    port->comDeb.qOutCount = 0;
+    port->comDeb.qOutHead  = 0;
+    port->comDeb.qOutTail  = 0;
     _enable();
 
+    dbgStr("COMM.DRV: setque OK\r\n");
     return 0;
 }
 
@@ -1105,6 +1424,8 @@ int16_t FAR PASCAL _export sndcom(int16_t commId, void FAR *buf, int16_t len)
     uint8_t FAR      *src;
     int16_t           bytesWritten;
 
+    dbgInt16("COMM.DRV: sndcom Id", commId);
+
     if (commId < 0 || commId >= MAX_PORTS) {
         return -1;
     }
@@ -1134,6 +1455,10 @@ int16_t FAR PASCAL _export sndcom(int16_t commId, void FAR *buf, int16_t len)
     }
     _enable();
 
+    // Sync ComDEB queue counts
+    port->comDeb.qOutCount = port->txCount;
+    port->comDeb.qOutHead  = port->txHead;
+
     // Prime transmitter if we wrote anything
     if (bytesWritten > 0 && !port->txStopped) {
         primeTx(port);
@@ -1154,12 +1479,16 @@ int16_t FAR PASCAL _export stacom(int16_t commId, COMSTAT FAR *stat)
     PortStateT *port;
     int16_t     errors;
 
+    dbgInt16("COMM.DRV: stacom Id", commId);
+
     if (commId < 0 || commId >= MAX_PORTS) {
+        dbgStr("COMM.DRV: stacom bad id\r\n");
         return -1;
     }
 
     port = &ports[commId];
     if (!port->isOpen) {
+        dbgStr("COMM.DRV: stacom not open\r\n");
         return -1;
     }
 
@@ -1177,6 +1506,7 @@ int16_t FAR PASCAL _export stacom(int16_t commId, COMSTAT FAR *stat)
         stat->cbOutQue = port->txCount;
     }
 
+    dbgHex16("COMM.DRV: stacom errors", (uint16_t)errors);
     return errors;
 }
 
@@ -1192,6 +1522,8 @@ void FAR PASCAL _export suspendOpenCommPorts(void)
     int16_t     i;
     PortStateT *port;
 
+    dbgStr("COMM.DRV: suspend\r\n");
+
     for (i = 0; i < MAX_PORTS; i++) {
         port = &ports[i];
         if (!port->isOpen) {
@@ -1221,12 +1553,15 @@ int16_t FAR PASCAL _export trmcom(int16_t commId)
 {
     PortStateT *port;
 
+    dbgInt16("COMM.DRV: trmcom Id", commId);
+
     if (commId < 0 || commId >= MAX_PORTS) {
         return -1;
     }
 
     port = &ports[commId];
     if (!port->isOpen) {
+        dbgStr("COMM.DRV: trmcom port not open\r\n");
         return -1;
     }
 
@@ -1252,6 +1587,8 @@ int16_t FAR PASCAL _export trmcom(int16_t commId)
 
     port->isOpen = FALSE;
 
+    dbgHex16("COMM.DRV: trmcom isrHits", isrHitCount);
+    dbgStr("COMM.DRV: trmcom OK\r\n");
     return 0;
 }
 
@@ -1268,6 +1605,8 @@ int FAR PASCAL LibMain(HANDLE hInstance, WORD wDataSeg, WORD wHeapSize, LPSTR lp
 
     ghInstance = hInstance;
 
+    dbgStr("COMM.DRV: LibMain\r\n");
+
     if (wHeapSize > 0) {
         UnlockData(0);
     }

drv/commdrv.def

@@ -20,8 +20,10 @@ EXPORTS
     CSETBRK                   @13
     CCLRBRK                   @14
     GETDCB                    @15
+    WEP                       @16 RESIDENTNAME
     SUSPENDOPENCOMMPORTS      @17
     REACTIVATEOPENCOMMPORTS   @18
     COMMWRITESTRING           @19
     READCOMMSTRING            @20
     ENABLENOTIFICATION        @100
+    COMMNOTIFYWNDPROC         @101

drv/commdrv.h

@@ -8,6 +8,7 @@
 #define COMMDRV_H
 
 #include <windows.h>
+#include <conio.h>
 
 // -----------------------------------------------------------------------
 // stdint types for MSVC 1.52 (no stdint.h available)
@@ -168,6 +169,7 @@ typedef signed char    int8_t;
 // exceeds 65535, high baud rates use CBR_* index constants instead
 // of raw values. Values >= 0xFF00 are indices, not raw rates.
 // -----------------------------------------------------------------------
+// Most CBR_* constants defined by windows.h; add any missing ones
 #ifndef CBR_110
 #define CBR_110    0xFF10
 #define CBR_300    0xFF11
@@ -176,10 +178,20 @@ typedef signed char    int8_t;
 #define CBR_2400   0xFF14
 #define CBR_4800   0xFF15
 #define CBR_9600   0xFF16
+#endif
+#ifndef CBR_14400
 #define CBR_14400  0xFF17
+#endif
+#ifndef CBR_19200
 #define CBR_19200  0xFF18
+#endif
+#ifndef CBR_38400
 #define CBR_38400  0xFF1B
+#endif
+#ifndef CBR_56000
 #define CBR_56000  0xFF1F
+#endif
+#ifndef CBR_115200
 #define CBR_115200 0xFF24
 #endif
 
@@ -189,15 +201,29 @@ typedef signed char    int8_t;
 #define FIFO_DEPTH 16
 
 // -----------------------------------------------------------------------
-// Comm error flags (CE_* -- matches Windows SDK definitions)
+// Comm error flags (CE_* -- most defined by windows.h, fill any gaps)
 // -----------------------------------------------------------------------
-#define CE_RXOVER   0x0001  // Receive Queue overflow
+#ifndef CE_RXOVER
-#define CE_OVERRUN  0x0002  // Hardware overrun
+#define CE_RXOVER   0x0001
-#define CE_RXPARITY 0x0004  // Parity error
+#endif
-#define CE_FRAME    0x0008  // Framing error
+#ifndef CE_OVERRUN
-#define CE_BREAK    0x0010  // Break detected
+#define CE_OVERRUN  0x0002
-#define CE_TXFULL   0x0020  // TX Queue is full
+#endif
-#define CE_MODE     0x8000  // Requested mode unsupported
+#ifndef CE_RXPARITY
+#define CE_RXPARITY 0x0004
+#endif
+#ifndef CE_FRAME
+#define CE_FRAME    0x0008
+#endif
+#ifndef CE_BREAK
+#define CE_BREAK    0x0010
+#endif
+#ifndef CE_TXFULL
+#define CE_TXFULL   0x0020
+#endif
+#ifndef CE_MODE
+#define CE_MODE     0x8000
+#endif
 
 // -----------------------------------------------------------------------
 // Comm event flags (EV_* -- matches Windows SDK definitions)
@@ -237,7 +263,10 @@ typedef signed char    int8_t;
 #define HS_BOTH    3
 
 // -----------------------------------------------------------------------
-// EscapeCommFunction codes (matches Windows SDK)
+// EscapeCommFunction codes
+//
+// SETXON through RESETDEV defined by windows.h.
+// SETBREAK/CLRBREAK are our extensions for routing through cextfcn.
 // -----------------------------------------------------------------------
 #ifndef SETXON
 #define SETXON    1
@@ -247,9 +276,9 @@ typedef signed char    int8_t;
 #define SETDTR    5
 #define CLRDTR    6
 #define RESETDEV  7
-#define SETBREAK  8
-#define CLRBREAK  9
 #endif
+#define ESC_SETBREAK  8
+#define ESC_CLRBREAK  9
 
 // -----------------------------------------------------------------------
 // Flush queue selectors
@@ -257,10 +286,48 @@ typedef signed char    int8_t;
 #define FLUSH_RX 0
 #define FLUSH_TX 1
 
+// -----------------------------------------------------------------------
+// Stock COMM.DRV compatible ComDEB structure
+//
+// SetCommEventMask (cevt) returns a FAR pointer to offset 0 of this
+// structure.  Third-party code (ProComm COMMTASK.DLL, etc.) accesses
+// fields at known offsets -- most importantly offset 35 (MSR shadow)
+// per Microsoft KB Q101417.  Our layout must match the stock driver.
+// -----------------------------------------------------------------------
+typedef struct {
+    uint16_t evtWord;       // +0:  Accumulated event flags (EV_*)
+    uint16_t evtMask;       // +2:  Event enable mask
+    uint16_t qInAddr;       // +4:  RX queue offset (compat, unused)
+    uint16_t qInSize;       // +6:  RX buffer size
+    uint16_t qInCount;      // +8:  RX bytes in buffer
+    uint16_t qInHead;       // +10: RX write position
+    uint16_t qInTail;       // +12: RX read position
+    uint16_t qOutAddr;      // +14: TX queue offset (compat, unused)
+    uint16_t qOutSize;      // +16: TX buffer size
+    uint16_t qOutCount;     // +18: TX bytes in buffer
+    uint16_t qOutHead;      // +20: TX write position
+    uint16_t qOutTail;      // +22: TX read position
+    uint16_t port;          // +24: UART base I/O address
+    uint16_t baudRate;      // +26: Current baud rate
+    uint8_t  lcrShadow;    // +28: LCR shadow
+    uint8_t  mcrShadow;    // +29: MCR shadow
+    uint8_t  ierShadow;    // +30: IER shadow
+    uint8_t  commErr;       // +31: Error flags (low byte)
+    uint8_t  flags1;        // +32: Internal flags
+    uint8_t  flags2;        // +33: More internal flags
+    uint8_t  recvTrigger;   // +34: FIFO trigger level
+    uint8_t  msrShadow;    // +35: MSR shadow (documented KB Q101417)
+    uint8_t  padding[4];    // +36: Pad to 40 bytes
+} ComDebT;
+
 // -----------------------------------------------------------------------
 // Port state structure
 // -----------------------------------------------------------------------
 typedef struct {
+    // Stock-compatible ComDEB -- must be kept synchronized.
+    // cevt returns a FAR pointer to this.
+    ComDebT  comDeb;
+
     uint16_t baseAddr;        // UART base I/O address
     uint8_t  irq;             // IRQ number (3 or 4)
     int16_t  commId;          // Port ID (0=COM1, 1=COM2, ...)
@@ -305,8 +372,6 @@ typedef struct {
     uint16_t errorFlags;      // CE_* error flags (sticky until read)
 
     // Event notification
-    uint16_t evtMask;         // Event enable mask
-    uint16_t evtWord;         // Accumulated events
     HWND     hwndNotify;      // Window for WM_COMMNOTIFY
     int16_t  rxNotifyThresh;  // CN_RECEIVE threshold (-1=disabled)
     int16_t  txNotifyThresh;  // CN_TRANSMIT threshold (-1=disabled)
@@ -328,14 +393,23 @@ typedef struct {
 // -----------------------------------------------------------------------
 extern PortStateT ports[MAX_PORTS];
 
+// -----------------------------------------------------------------------
+// Dynamically resolved PostMessage (USER.EXE not loaded at boot)
+// -----------------------------------------------------------------------
+typedef BOOL (FAR PASCAL *PostMessageProcT)(HWND, UINT, WPARAM, LPARAM);
+extern PostMessageProcT pfnPostMessage;
+
+// ISR hit counter for diagnostics
+extern volatile uint16_t isrHitCount;
+
 // -----------------------------------------------------------------------
 // Exported function prototypes (COMM.DRV API)
 //
 // These use the Windows COMM.DRV calling convention: FAR PASCAL
 // -----------------------------------------------------------------------
-int16_t FAR PASCAL _export inicom(DCB FAR *dcb, char FAR *rxBuf, int16_t rxSize);
+int16_t FAR PASCAL _export inicom(DCB FAR *dcb);
 int16_t FAR PASCAL _export setcom(DCB FAR *dcb);
-int16_t FAR PASCAL _export setque(int16_t commId, char FAR *rxBuf, int16_t rxSize, char FAR *txBuf, int16_t txSize);
+int16_t FAR PASCAL _export setque(int16_t commId, int16_t rxSize, int16_t txSize);
 int16_t FAR PASCAL _export reccom(int16_t commId, void FAR *buf, int16_t len);
 int16_t FAR PASCAL _export sndcom(int16_t commId, void FAR *buf, int16_t len);
 int16_t FAR PASCAL _export ctx(int16_t commId, int16_t ch);
@@ -347,12 +421,13 @@ int16_t FAR PASCAL _export cextfcn(int16_t commId, int16_t func);
 int16_t FAR PASCAL _export cflush(int16_t commId, int16_t queue);
 int16_t FAR PASCAL _export csetbrk(int16_t commId);
 int16_t FAR PASCAL _export cclrbrk(int16_t commId);
-int16_t FAR PASCAL _export getdcb(int16_t commId, DCB FAR *dcb);
+DCB FAR * FAR PASCAL _export getdcb(int16_t commId);
 void    FAR PASCAL _export suspendOpenCommPorts(void);
 void    FAR PASCAL _export reactivateOpenCommPorts(void);
 int16_t FAR PASCAL _export commWriteString(int16_t commId, void FAR *buf, int16_t len);
 int16_t FAR PASCAL _export readCommString(int16_t commId, void FAR *buf, int16_t len);
 int16_t FAR PASCAL _export enableNotification(int16_t commId, HWND hwnd, int16_t rxThresh, int16_t txThresh);
+int     FAR PASCAL _export commNotifyWndProc(void);
 
 // -----------------------------------------------------------------------
 // ISR prototypes (isr.c)

drv/isr.c

@@ -106,12 +106,12 @@ static void checkNotify(PortStateT *port)
     }
 
     // CN_EVENT: any event bits accumulated
-    if (port->evtWord & port->evtMask) {
+    if (port->comDeb.evtWord & port->comDeb.evtMask) {
         notifyBits |= CN_EVENT;
     }
 
-    if (notifyBits) {
+    if (notifyBits && pfnPostMessage) {
-        PostMessage(port->hwndNotify, WM_COMMNOTIFY, (WPARAM)port->commId, (LPARAM)notifyBits);
+        pfnPostMessage(port->hwndNotify, WM_COMMNOTIFY, (WPARAM)port->commId, (LPARAM)notifyBits);
     }
 }
 
@@ -132,10 +132,10 @@ static void handleLsr(PortStateT *port, uint8_t lsr)
     }
     if (lsr & LSR_BI) {
         port->errorFlags |= CE_BREAK;
-        port->evtWord |= EV_BREAK;
+        port->comDeb.evtWord |= EV_BREAK;
     }
     if (lsr & (LSR_OE | LSR_PE | LSR_FE)) {
-        port->evtWord |= EV_ERR;
+        port->comDeb.evtWord |= EV_ERR;
     }
 }
 
@@ -149,8 +149,11 @@ static void handleMsr(PortStateT *port)
 
     msr = (uint8_t)_inp(port->baseAddr + UART_MSR);
 
+    // Update ComDEB MSR shadow (offset 35) for third-party code
+    port->comDeb.msrShadow = msr;
+
     if (msr & MSR_DCTS) {
-        port->evtWord |= EV_CTS;
+        port->comDeb.evtWord |= EV_CTS;
 
         // RTS/CTS flow control: stop/start TX based on CTS
         if (port->hsMode == HS_RTSCTS || port->hsMode == HS_BOTH) {
@@ -167,15 +170,15 @@ static void handleMsr(PortStateT *port)
     }
 
     if (msr & MSR_DDSR) {
-        port->evtWord |= EV_DSR;
+        port->comDeb.evtWord |= EV_DSR;
     }
 
     if (msr & MSR_TERI) {
-        port->evtWord |= EV_RING;
+        port->comDeb.evtWord |= EV_RING;
     }
 
     if (msr & MSR_DDCD) {
-        port->evtWord |= EV_RLSD;
+        port->comDeb.evtWord |= EV_RLSD;
     }
 }
 
@@ -230,7 +233,7 @@ static void handleRx(PortStateT *port, uint8_t lsr)
         }
 
         // Set event bit
-        port->evtWord |= EV_RXCHAR;
+        port->comDeb.evtWord |= EV_RXCHAR;
 
         // Read LSR again for next byte
         lsr = (uint8_t)_inp(base + UART_LSR);
@@ -270,7 +273,7 @@ static void handleTx(PortStateT *port)
         // Nothing to send -- disable THRE interrupt
         _outp(base + UART_IER, (uint8_t)(_inp(base + UART_IER) & ~IER_THRE));
         // TX empty event
-        port->evtWord |= EV_TXEMPTY;
+        port->comDeb.evtWord |= EV_TXEMPTY;
         return;
     }
 
@@ -421,6 +424,14 @@ void isrDispatch(PortStateT *port)
         }
     }
 
+    // Sync queue counts into ComDEB for third-party code
+    port->comDeb.qInCount  = port->rxCount;
+    port->comDeb.qInHead   = port->rxHead;
+    port->comDeb.qInTail   = port->rxTail;
+    port->comDeb.qOutCount = port->txCount;
+    port->comDeb.qOutHead  = port->txHead;
+    port->comDeb.qOutTail  = port->txTail;
+
     checkNotify(port);
 }
 
@@ -478,6 +489,12 @@ void _far _interrupt isr3(void)
 {
     int16_t i;
 
+    // Load DLL's data segment -- _interrupt saves/restores DS but doesn't
+    // set it. Without this, DS belongs to whatever code was interrupted
+    // and all global accesses (ports[], ring buffers) read garbage.
+    _asm mov ax, seg ports
+    _asm mov ds, ax
+
     for (i = 0; i < MAX_PORTS; i++) {
         if (ports[i].isOpen && ports[i].irq == 3) {
             isrDispatch(&ports[i]);
@@ -496,6 +513,12 @@ void _far _interrupt isr4(void)
 {
     int16_t i;
 
+    // Load DLL's data segment -- see comment in isr3
+    _asm mov ax, seg ports
+    _asm mov ds, ax
+
+    isrHitCount++;
+
     for (i = 0; i < MAX_PORTS; i++) {
         if (ports[i].isOpen && ports[i].irq == 4) {
             isrDispatch(&ports[i]);

drv/makefile

@@ -28,9 +28,9 @@ LINK    = link
 #   -ASw    Small model, SS!=DS (Windows DLL)
 #   -Gsw    No stack probes, Windows prolog/epilog
 #   -Ow     Safe optimizations for Windows
-#   -Zp1    Pack structures on 1-byte boundaries (hardware register layouts)
+#   -Zp2    Pack structures on 2-byte boundaries (matches Windows SDK)
 #   -Ze     Enable Microsoft extensions
-CFLAGS  = -c -W3 -ASw -Gsw -Ow -Zp1 -Ze
+CFLAGS  = -c -W3 -ASw -Gsw -Ow -Zp2 -Ze
 
 # Linker flags:
 #   /NOD    No default libraries

vbx/makefile

@@ -61,7 +61,7 @@ OBJS    = mscomm.obj serial.obj
 # -----------------------------------------------------------------------
 all: $(TARGET)
 
-$(TARGET): $(OBJS) mscomm.def mscomm.res
+$(TARGET): $(OBJS) mscomm.def mscomm.res vbapi.lib
 	$(LINK) $(LFLAGS) $(OBJS), $(TARGET),,$(LIBS), mscomm.def
 	$(RC) mscomm.res $(TARGET)
 

vbx/mscomm.h

@@ -5,6 +5,13 @@
 #ifndef MSCOMM_H
 #define MSCOMM_H
 
+// -----------------------------------------------------------------------
+// Resource IDs
+// -----------------------------------------------------------------------
+#define IDB_MSCOMM 8000
+
+#ifndef RC_INVOKED
+
 #include "vbapi.h"
 #include "serial.h"
 
@@ -21,11 +28,6 @@ typedef signed char    int8_t;
 #define _STDINT_DEFINED
 #endif
 
-// -----------------------------------------------------------------------
-// Resource IDs
-// -----------------------------------------------------------------------
-#define IDB_MSCOMM 8000
-
 // -----------------------------------------------------------------------
 // Property indices (position in npproplist array)
 // -----------------------------------------------------------------------
@@ -138,4 +140,6 @@ typedef struct {
 // -----------------------------------------------------------------------
 extern HANDLE ghInstance;
 
+#endif // RC_INVOKED
+
 #endif // MSCOMM_H

vbx/serial.c

@@ -12,7 +12,7 @@
 // -----------------------------------------------------------------------
 int16_t serialClose(int16_t commId);
 int16_t serialConfigure(int16_t commId, int16_t port, const char FAR *settings);
-int16_t serialEnableNotify(int16_t commId, HWND hwnd, int16_t rxThreshold, int16_t txThreshold);
+BOOL    serialEnableNotify(int16_t commId, HWND hwnd, int16_t rxThreshold, int16_t txThreshold);
 int16_t serialEscape(int16_t commId, int16_t func);
 int16_t serialFlush(int16_t commId, int16_t queue);
 UINT    serialGetEventMask(int16_t commId, UINT mask);

vbx/serial.h

@@ -37,13 +37,17 @@ typedef signed char    int8_t;
 
 // -----------------------------------------------------------------------
 // Escape function constants (mirrors EscapeCommFunction values)
+//
+// SETDTR through RESETDEV are defined by windows.h.
+// SETBREAK/CLRBREAK are not in windows.h (SetCommBreak/ClearCommBreak
+// are separate API functions), so we define numeric values directly.
 // -----------------------------------------------------------------------
 #define SERIAL_SETDTR    SETDTR
 #define SERIAL_CLRDTR    CLRDTR
 #define SERIAL_SETRTS    SETRTS
 #define SERIAL_CLRRTS    CLRRTS
-#define SERIAL_SETBREAK  SETBREAK
+#define SERIAL_SETBREAK  8
-#define SERIAL_CLRBREAK  CLRBREAK
+#define SERIAL_CLRBREAK  9
 
 // -----------------------------------------------------------------------
 // Function prototypes

vbx/vbapi.h

@@ -17,17 +17,15 @@
 // -----------------------------------------------------------------------
 // Core types
 // -----------------------------------------------------------------------
+#ifndef USHORT
+typedef unsigned short USHORT;
+#endif
+
 typedef WORD   HCTL;           // Handle to a VBX control instance
 typedef WORD   HSZ;            // Handle to a VB-managed string
 typedef LONG   HLSTR;          // Handle to a VB long string
 typedef USHORT ERR;            // Error code
 
-// Segment type for MSVC 1.52
-#ifndef _SEGMENT_DEFINED
-typedef unsigned short _segment;
-#define _SEGMENT_DEFINED
-#endif
-
 // Flag type
 typedef DWORD FL;
 
@@ -196,7 +194,7 @@ struct tagMODEL {
     FL          fl;                  // MODEL_* flags
     PCTLPROC    pctlproc;           // Control procedure
     USHORT      fsClassStyle;        // Window class style bits
-    USHORT      flWndStyle;          // Window style bits
+    FL          flWndStyle;          // Window style bits
     USHORT      cbCtlExtra;          // Bytes of per-instance data
     USHORT      idBmpPalette;        // Toolbox bitmap resource ID
     PSTR        npszDefCtlName;      // Default control name (near)