#476 Hang in ctext with regexp match

[Neil Madden]

Just been playing with ctext and I ran into a bug which causes an
endless loop on my system. The problem came from trying to
highlight Tcl comments, using:

ctext::addHighlightClassForRegexp $win comment navy
{#[^\n]*\n}

Then if I add the following to the text widget:

This is a test
# This is a test
foo

Then position the cursor somewhere in the comment, and press
backspace - endless loop occurs in ctext::highlight - the third while
1 loop. Problem seems to be that the [$win search..] stuff is
passed indices like 4.0 3.15 (i.e. start is after end), and it return
3.0 bizarrely (this may be a bug in the text widget, or possibly in
the Mac OS X implementation - I haven't followed up yet). The fix
was to add these lines after the {"" == $res} check:

# If result given is less than the start index (can happen), then
# break out
foreach {l1 c1} [split $res .] {l2 c2} [split $si .] { break }
if {$l1 < $l2 || ($l1 == $l2 && $c1 < $c2)} { break }

Everything seems to work again after adding that in. I would
upload a patch, but I'm very busy at present. Hassle me by email
if you really really want a patch!

[Anonymous]

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user_id=585068

This failure only occurs with Tk 8.5/HEAD. I can't
duplicate it with 8.4.6.

With 8.4.6 this *does not* work:
ctext::addHighlightClassForRegexp .ct comment navy {#[^\n]*\n}
That same RE works properly in 8.5/HEAD.

This RE always seems to work (and interestingly seems to
avoid the endless loop with 8.5):
ctext::addHighlightClassForRegexp .ct comment khaki {#[^\n\r]*}

Time to file a bug for Tk I think.