--- /home/fellowsd/lang/tcl/cvs/tcl/unix/tclUnixChan.c	Thu Feb 28 14:26:21 2002
+++ tclUnixChan.c	Tue Mar  5 16:12:40 2002
@@ -669,11 +669,17 @@
     ClientData instanceData;	/* Tty state. */
     Tcl_Interp *interp;		/* For error reporting - unused. */
 {
-    TtyState *ttyPtr;
+    TtyState *ttyPtr = (TtyState *) instanceData;
 
-    ttyPtr = (TtyState *) instanceData;
+    /*
+     * Only hard-flush channels that are not stdout and not stderr,
+     * otherwise debugging output sent to terminals can get lost!
+     * Tcl bug #525783
+     */
 #ifdef TTYFLUSH
-    TTYFLUSH(ttyPtr->fs.fd);
+    if (ttyPtr->fs.fd!=1 && ttyPtr->fs.fd!=2) {
+	TTYFLUSH(ttyPtr->fs.fd);
+    }
 #endif
 #if 0
     /*
@@ -720,10 +726,14 @@
     int toWrite;			/* How many bytes to write? */
     int *errorCodePtr;			/* Where to store error code. */
 {
-    if ( TclInExit() ) {
+    TtyState *ttyPtr = (TtyState *) instanceData;
+
+    if (ttyPtr->fs.fd!=1 && ttyPtr->fs.fd!=2 && TclInExit()) {
 	/*
-	 * Do not write data during Tcl exit.
-	 * Serial port may block preventing Tcl from exit.
+	 * Do not write data during Tcl exit (except to stdout and
+	 * stderr.) Serial port may block preventing Tcl from exit.
+	 * Note that stdout and stderr are excepted because of the
+	 * impact on interactive debugging...
 	 */
 	return toWrite;
     } else {