* 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.

4 files changed, 96 insertions, 5 deletions

diff --git a/ChangeLog b/ChangeLog
index 70bd297..99ffef6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,28 @@
+2004-07-14  Andreas Kupries  <andreask@activestate.com>
+
+	* 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.
+
+2004-06-14  Andreas Kupries  <andreask@activestate.com>
+
+	* 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.
+
 2004-07-15  Andreas Kupries  <andreask@pliers.activestate.com>
 
 	* generic/tclIOCmd.c (Tcl_PutsObjCmd): Added length check to the
@@ -190,8 +215,8 @@
 
 2004-05-19  Andreas Kupries  <andreask@activestate.com>
 
-	* tclIO.c: Fixed [SF Tcl Bug 943274]. This is the same problem as
-	* tclIO.h: [SF Tcl Bug 462317], see ChangeLog entry
+	* generic/tclIO.c: Fixed [SF Tcl Bug 943274]. This is the same problem as
+	* generic/tclIO.h: [SF Tcl Bug 462317], see ChangeLog entry
 	           2001-09-26. The fix done at that time is incomplete. It
 	           is possible to get around it if the actual read
 	           operation is defered and not executed in the event
@@ -202,6 +227,8 @@
 	           actual data waiting. The flag is cleared by a short or
 	           full read.
 
+	  ***POTENTIAL INCOMPATIBILITY*** for channel drivers.
+
 2004-05-18  Kevin B. Kenny  <kennykb@acm.org>
 
 	* compat/strftime.c (_fmt, ISO8601Week):
diff --git a/doc/CrtChannel.3 b/doc/CrtChannel.3
index 477ef67..828b958 100644
--- a/doc/CrtChannel.3
+++ b/doc/CrtChannel.3
@@ -5,7 +5,7 @@
 '\" See the file "license.terms" for information on usage and redistribution
 '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 '\"
-'\" RCS: @(#) $Id: CrtChannel.3,v 1.16 2002/07/01 18:24:39 jenglish Exp $
+'\" RCS: @(#) $Id: CrtChannel.3,v 1.16.2.1 2004/07/15 20:46:17 andreas_kupries Exp $
 .so man.macros
 .TH Tcl_CreateChannel 3 8.3 Tcl "Tcl Library Procedures"
 .BS
@@ -405,6 +405,14 @@ behavior must be emulated in the channel driver.
 .PP
 This value can be retrieved with \fBTcl_ChannelBlockModeProc\fR, which returns
 a pointer to the function.
+.PP
+A channel driver \fBnot\fR supplying a \fIblockModeProc\fR has to be
+very, very careful. It has to tell the generic layer exactly which
+blocking mode is acceptable to it, and should this also document for
+the user so that the blocking mode of the channel is not changed to an
+inacceptable value. Any confusion here may lead the interpreter into a
+(spurious and difficult to find) deadlock.
+
 
 .SH "CLOSEPROC AND CLOSE2PROC"
 .PP
diff --git a/generic/tclIO.c b/generic/tclIO.c
index f1a3266..154bec0 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 1.61.2.6 2004/05/19 19:23:58 andreas_kupries Exp $
+ * RCS: @(#) $Id: tclIO.c,v 1.61.2.7 2004/07/15 20:46:18 andreas_kupries Exp $
  */
 
 #include "tclInt.h"
@@ -772,6 +772,7 @@ Tcl_RegisterChannel(interp, chan)
         }
         Tcl_SetHashValue(hPtr, (ClientData) chanPtr);
     }
+
     statePtr->refCount++;
 }
 
@@ -808,6 +809,17 @@ 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;
     }
@@ -2527,6 +2539,14 @@ Tcl_Close(interp, chan)
     if (statePtr->refCount > 0) {
         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
@@ -2551,6 +2571,8 @@ Tcl_Close(interp, chan)
         ckfree((char *) cbPtr);
     }
 
+    statePtr->flags &= ~CHANNEL_INCLOSE;
+
     /*
      * Ensure that the last output buffer will be flushed.
      */
@@ -4225,6 +4247,7 @@ 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
@@ -4240,6 +4263,7 @@ 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
@@ -4251,7 +4275,9 @@ 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
@@ -4265,11 +4291,13 @@ 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;
@@ -5310,6 +5338,7 @@ 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
@@ -5324,9 +5353,14 @@ 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;
@@ -5342,11 +5376,13 @@ 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;
@@ -6740,6 +6776,7 @@ 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
@@ -6753,6 +6790,7 @@ 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
@@ -6993,6 +7031,7 @@ 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
@@ -7004,10 +7043,15 @@ 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;
@@ -9239,8 +9283,11 @@ 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 7f2c421..ea3c6e4 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 1.5.4.1 2004/05/19 19:16:24 andreas_kupries Exp $
+ * RCS: @(#) $Id: tclIO.h,v 1.5.4.2 2004/07/15 20:46:19 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,