From 81d499ea3132322afb4b7b97c56a949ad04609ac Mon Sep 17 00:00:00 2001
From: pooryorick <com.digitalsmarties@pooryorick.com>
Date: Mon, 26 Apr 2021 23:06:14 +0000
Subject: Fix for io-28.6.

---
 generic/tclIO.c      | 40 ++++++++++++++++++++++++----------------
 generic/tclIORChan.c |  8 ++++----
 2 files changed, 28 insertions(+), 20 deletions(-)

diff --git a/generic/tclIO.c b/generic/tclIO.c
index fd87520..b9ec2a7 100644
--- a/generic/tclIO.c
+++ b/generic/tclIO.c
@@ -3660,7 +3660,7 @@ Tcl_CloseEx(
      * That won't do.
      */
 
-    if (statePtr->flags & CHANNEL_INCLOSE) {
+    if (GotFlag(statePtr, CHANNEL_INCLOSE)) {
 	if (interp) {
 	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
                     "illegal recursive call to close through close-handler"
@@ -8605,9 +8605,12 @@ ChannelTimerProc(
     ClientData clientData)
 {
     Channel *chanPtr = (Channel *)clientData;
+
+    /* State info for channel */
     ChannelState *statePtr = chanPtr->state;
-				/* State info for channel */
 
+	/* Preserve chanPtr to guard against deallocation in Tcl_NotifyChannel. */
+    TclChannelPreserve((Tcl_Channel)chanPtr);
     Tcl_Preserve(statePtr);
     statePtr->timer = NULL;
     if (statePtr->interestMask & TCL_WRITABLE
@@ -8623,22 +8626,27 @@ ChannelTimerProc(
 	Tcl_NotifyChannel((Tcl_Channel) chanPtr, TCL_WRITABLE);
     }
 
-    if (!GotFlag(statePtr, CHANNEL_NEED_MORE_DATA)
-	    && (statePtr->interestMask & TCL_READABLE)
-	    && (statePtr->inQueueHead != NULL)
-	    && IsBufferReady(statePtr->inQueueHead)) {
-	/*
-	 * Restart the timer in case a channel handler reenters the event loop
-	 * before UpdateInterest gets called by Tcl_NotifyChannel.
-	 */
+    /* The channel may have just been closed from within Tcl_NotifyChannel */
+    if (!GotFlag(statePtr, CHANNEL_INCLOSE)) {
+	if (!GotFlag(statePtr, CHANNEL_NEED_MORE_DATA)
+		&& (statePtr->interestMask & TCL_READABLE)
+		&& (statePtr->inQueueHead != NULL)
+		&& IsBufferReady(statePtr->inQueueHead)) {
+	    /*
+	     * Restart the timer in case a channel handler reenters the event loop
+	     * before UpdateInterest gets called by Tcl_NotifyChannel.
+	     */
 
-	statePtr->timer = Tcl_CreateTimerHandler(SYNTHETIC_EVENT_TIME,
-                ChannelTimerProc,chanPtr);
-	Tcl_NotifyChannel((Tcl_Channel) chanPtr, TCL_READABLE);
-    } else {
-	UpdateInterest(chanPtr);
+	    statePtr->timer = Tcl_CreateTimerHandler(SYNTHETIC_EVENT_TIME,
+		    ChannelTimerProc,chanPtr);
+	    Tcl_NotifyChannel((Tcl_Channel) chanPtr, TCL_READABLE);
+	} else {
+	    UpdateInterest(chanPtr);
+	}
     }
+
     Tcl_Release(statePtr);
+    TclChannelRelease((Tcl_Channel)chanPtr);
 }
 
 /*
@@ -8703,7 +8711,7 @@ Tcl_CreateChannelHandler(
 
     /*
      * The remainder of the initialization below is done regardless of whether
-     * or not this is a new record or a modification of an old one.
+     * this is a new record or a modification of an old one.
      */
 
     chPtr->mask = mask;
diff --git a/generic/tclIORChan.c b/generic/tclIORChan.c
index 88f6de8..9097bf4 100644
--- a/generic/tclIORChan.c
+++ b/generic/tclIORChan.c
@@ -80,7 +80,7 @@ static const Tcl_ChannelType tclRChannelType = {
     ReflectGetOption,	   /* Get options.			NULL'able */
     ReflectWatch,	   /* Initialize notifier			  */
     NULL,		   /* Get OS handle from the channel.	NULL'able */
-	ReflectClose,	   /* No close2 support.		NULL'able */
+    ReflectClose,	   /* No close2 support.		NULL'able */
     ReflectBlock,	   /* Set blocking/nonblocking.		NULL'able */
     NULL,		   /* Flush channel. Not used by core.	NULL'able */
     NULL,		   /* Handle events.			NULL'able */
@@ -1156,7 +1156,7 @@ TclChanCaughtErrorBypass(
  * ReflectClose --
  *
  *	This function is invoked when the channel is closed, to delete the
- *	driver specific instance data.
+ *	driver-specific instance data.
  *
  * Results:
  *	A posix error.
@@ -1189,8 +1189,8 @@ ReflectClose(
 	/*
 	 * This call comes from TclFinalizeIOSystem. There are no
 	 * interpreters, and therefore we cannot call upon the handler command
-	 * anymore. Threading is irrelevant as well. We simply clean up all
-	 * our C level data structures and leave the Tcl level to the other
+	 * anymore. Threading is irrelevant as well. Simply clean up all
+	 * the C level data structures and leave the Tcl level to the other
 	 * finalization functions.
 	 */
 
-- 
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