Added comment explaining the "knownBug" in iogt-6.1

1 files changed, 9 insertions, 0 deletions

diff --git a/tests/iogt.test b/tests/iogt.test
index 50034de..33a6425 100644
--- a/tests/iogt.test
+++ b/tests/iogt.test
@@ -839,6 +839,15 @@ test iogt-6.0 {Push back} -constraints testchannel -body {
     close $f
 } -result {xxx}
 test iogt-6.1 {Push back and up} -constraints {testchannel knownBug} -body {
+
+    # This test demonstrates the bug/misfeature in the stacked
+    # channel implementation that data can be discarded if it is
+    # read into the buffers of one channel in the stack, and then
+    # that channel is popped before anything above it reads.
+    #
+    # This bug can be worked around by always setting -buffersize
+    # to 1, but who wants to do that?
+
     set f [open $path(dummy) r]
     # contents of dummy = "abcdefghi..."
     read $f 3;		# skip behind "abc"