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authorandreas_kupries <akupries@shaw.ca>2003-04-11 17:35:30 (GMT)
committerandreas_kupries <akupries@shaw.ca>2003-04-11 17:35:30 (GMT)
commit89975c594f663fa730e70a1d45ba4e4aedb9aed8 (patch)
treee11b3e273ce55293fd3b461371c4824d69f126c6
parentd5f0a961d91663c289bcfab20356dfb54493659a (diff)
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* generic/tclIO.c (UpdateInterest): When dropping interest in
TCL_READABLE now dropping interest in TCL_EXCEPTION too. This fixes a bug where Expect detects eof on a file prematurely on solaris 2.6 and higher. A much more complete explanation is in the code itself (40 lines of comments for a one-line change :)
-rw-r--r--ChangeLog8
-rw-r--r--generic/tclIO.c45
2 files changed, 46 insertions, 7 deletions
diff --git a/ChangeLog b/ChangeLog
index ecb0883..c48934e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2003-04-11 Andreas Kupries <andreask@activestate.com>
+
+ * generic/tclIO.c (UpdateInterest): When dropping interest in
+ TCL_READABLE now dropping interest in TCL_EXCEPTION too. This
+ fixes a bug where Expect detects eof on a file prematurely on
+ solaris 2.6 and higher. A much more complete explanation is in
+ the code itself (40 lines of comments for a one-line change :)
+
2003-04-10 Donal K. Fellows <fellowsd@cs.man.ac.uk>
* doc/binary.n: Fixed typo in [binary format w] desc. [Bug 718543]
diff --git a/generic/tclIO.c b/generic/tclIO.c
index d4177c1..6ef2b5e 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 1.61.2.1 2003/04/10 22:18:07 andreas_kupries Exp $
+ * RCS: @(#) $Id: tclIO.c,v 1.61.2.2 2003/04/11 17:35:33 andreas_kupries Exp $
*/
#include "tclInt.h"
@@ -6852,15 +6852,46 @@ UpdateInterest(chanPtr)
mask &= ~TCL_READABLE;
/*
- * Andreas Kupries -- Experimental change
+ * Andreas Kupries, April 11, 2003
*
- * Squash interest in exceptions too. Solaris may/will
- * generate superfluous exceptions for plain text files,
- * screwing up expect, which doesn't get the synthesized
- * readable event, or to late.
+ * Some operating systems (Solaris 2.6 and higher (but not
+ * Solaris 2.5, go figure)) generate READABLE and
+ * EXCEPTION events when select()'ing [*] on a plain file,
+ * even if EOF was not yet reached. This is a problem in
+ * the following situation:
+ *
+ * - An extension asks to get both READABLE and EXCEPTION
+ * events.
+ * - It reads data into a buffer smaller than the buffer
+ * used by Tcl itself.
+ * - It does not process all events in the event queue, but
+ * only only one, at least in some situations.
+ *
+ * In that case we can get into a situation where
+ *
+ * - Tcl drops READABLE here, because it has data in its own
+ * buffers waiting to be read by the extension.
+ * - A READABLE event is syntesized via timer.
+ * - The OS still reports the EXCEPTION condition on the file.
+ * - And the extension gets the EXCPTION event first, and
+ * handles this as EOF.
+ *
+ * End result ==> Premature end of reading from a file.
+ *
+ * The concrete example is 'Expect', and its [expect]
+ * command (and at the C-level, deep in the bowels of
+ * Expect, 'exp_get_next_event'. See marker 'SunOS' for
+ * commentary in that function too).
+ *
+ * [*] As the Tcl notifier does. See also for marker
+ * 'SunOS' in file 'exp_event.c' of Expect.
+ *
+ * Our solution here is to drop the interest in the
+ * EXCEPTION events too. This compiles on all platforms,
+ * and also passes the testsuite on all of them.
*/
- mask &= ~TCL_EXCEPTION;
+ mask &= ~TCL_EXCEPTION;
if (!statePtr->timer) {
statePtr->timer = Tcl_CreateTimerHandler(0, ChannelTimerProc,