Stop the segfault in iogt-2.4. First by changing the UpdateInterest()

call that triggers it.  "downChanPtr" may no longer be the right argument
at that point.  Second, after ending the segfault, the test became an 
infinite loop (nested unstacking?!  whoa.), so revised the test to one
that terminates (and passes).  Left behind a comment that the recursive
unstacking case may require more examination.

1 files changed, 8 insertions, 1 deletions

diff --git a/generic/tclIO.c b/generic/tclIO.c
index 776ff12..a83cdcd 100644
--- a/generic/tclIO.c
+++ b/generic/tclIO.c
@@ -1876,6 +1876,13 @@ Tcl_UnstackChannel(
 	 * into the old structure.
 	 */
 
+	/*
+	 * TODO: Figure out how to handle the situation where the chan
+	 * operations called below by this unstacking operation cause
+	 * another unstacking recursively.  In that case the downChanPtr
+	 * value we're holding on to will not be the right thing.
+	 */
+
 	Channel *downChanPtr = chanPtr->downChanPtr;
 
 	/*
@@ -1980,7 +1987,7 @@ Tcl_UnstackChannel(
 	 */
 
 	Tcl_EventuallyFree(chanPtr, TCL_DYNAMIC);
-	UpdateInterest(downChanPtr);
+	UpdateInterest(statePtr->topChanPtr);
 
 	if (result != 0) {
 	    Tcl_SetErrno(result);