* generic/tclIO.h (CHANNEL_INCLOSE): New flag. Set in

	* generic/tclIO.c (Tcl_UnregisterChannel): 'Tcl_Close' while the
	* generic/tclIO.c (Tcl_Close):             close callbacks are
	  run. Checked in 'Tcl_Close' and 'Tcl_Unregister' to prevent
	  recursive call of 'close' in the close-callbacks. This is a
	  possible error made by implementors of virtual filesystems based
	  on 'tclvfs', thinking that they have to close the channel in the
	  close handler for the filesystem.

	* generic/tclIO.c:
	* generic/tclIO.h:
	* Not reverting, but #ifdef'ing the changes from May 19, 2004 out
	  of the core. This removes the ***POTENTIAL INCOMPATIBILITY***
	  for channel drivers it introduced. This has become possible due
	  to Expect gaining a BlockModeProc and now handling blockingg and
	  non-blocking modes correctly. Thus [SF Tcl Bug 943274] is still
	  fixed if a recent enough version of Expect is used.

	* doc/CrtChannel.3: Added warning about usage of a channel without
	  a BlockModeProc.

2 files changed, 55 insertions, 2 deletions

diff --git a/generic/tclIO.c b/generic/tclIO.c
index 919dfef..295225c 100644
--- a/generic/tclIO.c
+++ b/generic/tclIO.c
@@ -10,7 +10,7 @@
  * See the file "license.terms" for information on usage and redistribution
  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclIO.c,v 1.76 2004/06/01 18:44:16 davygrvy Exp $
+ * RCS: @(#) $Id: tclIO.c,v 1.77 2004/07/15 20:46:49 andreas_kupries Exp $
  */
 
 #include "tclInt.h"
@@ -807,6 +807,17 @@ Tcl_UnregisterChannel(interp, chan)
 {
     ChannelState *statePtr;	/* State of the real channel. */
 
+    statePtr = ((Channel *) chan)->state->bottomChanPtr->state;
+
+    if (statePtr->flags & CHANNEL_INCLOSE) {
+        if (interp != (Tcl_Interp*) NULL) {
+	    Tcl_AppendResult(interp, 
+	     "Illegal recursive call to close through close-handler of channel",
+	     (char *) NULL);
+	}
+	return TCL_ERROR;
+    }
+
     if (DetachChannel(interp, chan) != TCL_OK) {
         return TCL_OK;
     }
@@ -2529,6 +2540,14 @@ Tcl_Close(interp, chan)
         Tcl_Panic("called Tcl_Close on channel with refCount > 0");
     }
 
+    if (statePtr->flags & CHANNEL_INCLOSE) {
+        Tcl_AppendResult(interp,
+	 "Illegal recursive call to close through close-handler of channel",
+	 (char *) NULL);
+        return TCL_ERROR;
+    }
+    statePtr->flags |= CHANNEL_INCLOSE;
+
     /*
      * When the channel has an escape sequence driven encoding such as
      * iso2022, the terminated escape sequence must write to the buffer.
@@ -2552,6 +2571,8 @@ Tcl_Close(interp, chan)
         ckfree((char *) cbPtr);
     }
 
+    statePtr->flags &= ~CHANNEL_INCLOSE;
+
     /*
      * Ensure that the last output buffer will be flushed.
      */
@@ -4237,6 +4258,7 @@ Tcl_ReadRaw(chan, bufPtr, bytesToRead)
                 statePtr->flags &= (~(CHANNEL_BLOCKED));
             }
 
+#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
 	    /* [SF Tcl Bug 943274]. Better emulation of non-blocking
 	     * channels for channels without BlockModeProc, by keeping
 	     * track of true fileevents generated by the OS == Data
@@ -4252,6 +4274,7 @@ Tcl_ReadRaw(chan, bufPtr, bytesToRead)
 	        nread  = -1;
 	        result = EWOULDBLOCK;
 	    } else {
+#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
 	      /*
 	       * Now go to the driver to get as much as is possible to
 	       * fill the remaining request. Do all the error handling
@@ -4263,7 +4286,9 @@ Tcl_ReadRaw(chan, bufPtr, bytesToRead)
 
 	      nread = (chanPtr->typePtr->inputProc)(chanPtr->instanceData,
 			  bufPtr + copied, bytesToRead - copied, &result);
+#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
 	    }
+#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
 	    if (nread > 0) {
 	        /*
 		 * If we get a short read, signal up that we may be
@@ -4277,11 +4302,13 @@ Tcl_ReadRaw(chan, bufPtr, bytesToRead)
 		    statePtr->flags |= CHANNEL_BLOCKED;
 		}
 
+#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
 	        if (nread <= (bytesToRead - copied)) {
 		    /* [SF Tcl Bug 943274] We have read the available
 		     * data, clear flag */
 		    statePtr->flags &= ~CHANNEL_HAS_MORE_DATA;
 		}
+#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
 	    } else if (nread == 0) {
 	        statePtr->flags |= CHANNEL_EOF;
 		statePtr->inputEncodingFlags |= TCL_ENCODING_END;
@@ -5323,6 +5350,7 @@ GetInput(chanPtr)
 	return 0;
     }
 
+#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
     /* [SF Tcl Bug 943274]. Better emulation of non-blocking channels
      * for channels without BlockModeProc, by keeping track of true
      * fileevents generated by the OS == Data waiting and reading if
@@ -5337,9 +5365,12 @@ GetInput(chanPtr)
         nread = -1;
         result = EWOULDBLOCK;
     } else {
+#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
         nread = (chanPtr->typePtr->inputProc)(chanPtr->instanceData,
 		    bufPtr->buf + bufPtr->nextAdded, toRead, &result);
+#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
     }
+#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
 
     if (nread > 0) {
 	bufPtr->nextAdded += nread;
@@ -5355,11 +5386,13 @@ GetInput(chanPtr)
 	    statePtr->flags |= CHANNEL_BLOCKED;
 	}
 
+#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
 	if (nread <= toRead) {
 	  /* [SF Tcl Bug 943274] We have read the available data,
 	   * clear flag */
 	  statePtr->flags &= ~CHANNEL_HAS_MORE_DATA;
 	}
+#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
 
     } else if (nread == 0) {
 	statePtr->flags |= CHANNEL_EOF;
@@ -6764,6 +6797,7 @@ Tcl_NotifyChannel(channel, mask)
     Channel* upChanPtr;
     Tcl_ChannelType* upTypePtr;
 
+#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
     /* [SF Tcl Bug 943274]
      * For a non-blocking channel without blockmodeproc we keep track
      * of actual input coming from the OS so that we can do a credible
@@ -6777,6 +6811,7 @@ Tcl_NotifyChannel(channel, mask)
 
         statePtr->flags |= CHANNEL_HAS_MORE_DATA;
     }
+#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
 
     /*
      * In contrast to the other API functions this procedure walks towards
@@ -7017,6 +7052,7 @@ ChannelTimerProc(clientData)
 	statePtr->timer = Tcl_CreateTimerHandler(0, ChannelTimerProc,
 		(ClientData) chanPtr);
 
+#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
 	/* Set the TIMER flag to notify the higher levels that the
 	 * driver might have no data for us. We do this only if we are
 	 * in non-blocking mode and the driver has no BlockModeProc
@@ -7028,10 +7064,15 @@ ChannelTimerProc(clientData)
 	    (Tcl_ChannelBlockModeProc(chanPtr->typePtr) == NULL)) {
 	    statePtr->flags |= CHANNEL_TIMER_FEV;
 	}
+#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
+
 	Tcl_Preserve((ClientData) statePtr);
 	Tcl_NotifyChannel((Tcl_Channel)chanPtr, TCL_READABLE);
 
+#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
 	statePtr->flags &= ~CHANNEL_TIMER_FEV; 
+#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
+
 	Tcl_Release((ClientData) statePtr);
     } else {
 	statePtr->timer = NULL;
@@ -9263,8 +9304,11 @@ DumpFlags (str, flags)
   if (flags & INPUT_NEED_NL)          {buf[i] = '*';} else {buf [i]='_';}; i++;
   if (flags & CHANNEL_DEAD)           {buf[i] = 'D';} else {buf [i]='_';}; i++;
   if (flags & CHANNEL_RAW_MODE)       {buf[i] = 'R';} else {buf [i]='_';}; i++;
+#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
   if (flags & CHANNEL_TIMER_FEV)      {buf[i] = 'T';} else {buf [i]='_';}; i++;
   if (flags & CHANNEL_HAS_MORE_DATA)  {buf[i] = 'H';} else {buf [i]='_';}; i++;
+#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
+  if (flags & CHANNEL_INCLOSE)        {buf[i] = 'x';} else {buf [i]='_';}; i++;
   buf [i] ='\0';
 
   fprintf (stderr,"%s: %s\n", str, buf); fflush(stderr);
diff --git a/generic/tclIO.h b/generic/tclIO.h
index a4eefd3..c0abec2 100644
--- a/generic/tclIO.h
+++ b/generic/tclIO.h
@@ -10,7 +10,7 @@
  * See the file "license.terms" for information on usage and redistribution
  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclIO.h,v 1.6 2004/05/19 19:41:10 andreas_kupries Exp $
+ * RCS: @(#) $Id: tclIO.h,v 1.7 2004/07/15 20:46:49 andreas_kupries Exp $
  */
 
 /*
@@ -296,6 +296,7 @@ typedef struct ChannelState {
 					 * the state of the channel changes. */
 #define CHANNEL_RAW_MODE	(1<<16)	/* When set, notes that the Raw API is
 					 * being used. */
+#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
 #define CHANNEL_TIMER_FEV       (1<<17) /* When set the event we are
 					 * notified by is a fileevent
 					 * generated by a timer. We
@@ -323,6 +324,14 @@ typedef struct ChannelState {
 					 * will be performed if the
 					 * flag is set. This will
 					 * reset the flag as well. */
+#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
+
+#define CHANNEL_INCLOSE		(1<<19)	/* Channel is currently being
+					 * closed. Its structures are
+					 * still live and usable, but
+					 * it may not be closed again
+					 * from within the close handler.
+					 */
 
 /*
  * For each channel handler registered in a call to Tcl_CreateChannelHandler,