Bob Rogers <[EMAIL PROTECTED]> wrote:
From: Leopold Toetsch <[EMAIL PROTECTED]>
Date: Mon, 18 Sep 2006 11:53:36 +0200
Am Montag, 18. September 2006 03:56 schrieb Bob Rogers:
> The attached patch consolidates most of the existing stack-unwinding
> code into Continuation:invoke; previously, RetContinuation:invoke and
> find_exception_handler also did stack-unwinding, and none of the three
> did it quite the same way.
Very good.
Thanks.
Unfortunately, this patch breaks Tcl. There seems to be some bug with
exceptions.
Here's the Tcl used for this example:
proc test {} {uplevel #0 {append}}
test
[uplevel] executes its argument in another scope. In this case, it's
executing [append] in the global scope. This [append] call will throw
an exception because it hasn't passed enough arguments. [uplevel]
catches the exception so it can restore the call stack and then
rethrows the exception.
The code for this can be found in
languages/tcl/runtime/builtin/uplevel.pir (the actual catch happens on
line 68). The .catch() and .rethrow() macros are defined in
languages/tcl/src/macros.pir.
What's actually happening when I run this code is that the [uplevel]
code restores the call stack and rethrows the exception... and then
somehow catches it again (this is the bug), which causes a
ResizablePMCArray "can't pop from empty array" error.
I tried to write up a small test case demonstrating what the problem
was, but none of my guesses of what's causing it were correct. I hope
I've given you enough information to fix it. If I haven't, let me know
what else I can provide.
Thanks,
--
Matt Diephouse
http://matt.diephouse.com
