bugText Extractor TXR - Bugs: bug #34863, Particular invalid input triggers...


bug #34863: Particular invalid input triggers start condition underflow in scanner.

Submitted by:  Kaz Kylheku <kkylheku>
Submitted on:  Sat 19 Nov 2011 05:41:19 AM UTC  
Category:  None Severity:  2 - Minor
Item Group:  Correctness Status:  Fixed
Privacy:  Public Assigned to:  Kaz Kylheku <kkylheku>
Originator Name:  Open/Closed:  Closed
Component Version:  None Operating System:  None
Fixed Release:  None Planned Release:  None
Architecture:  All ABI:  All

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Thu 10 Oct 2013 05:49:38 AM UTC, comment #1:

Okay, now this is quite interesting.

I tried that on git head (just after Version 68) and the problem did not reproduce!

I searched my working directory and found a .txr file with the test case for this, last modified February 2012:

$ ls -l start-condition-stack-oflow.txr
-rw-r--r-- 1 kaz kaz 23 Feb 4 2012 start-condition-stack-oflow.txr

Was I looking at this at that time? I checked out some revisions of txr from around the time, but the problem did not reproduce. On the date when that file was last touched, the problem was already gone.

Intrigued, I performed a "git bisect" to find when the problem went away. Which commit fixed it?

It turns out to be the "Critical regression" fix to hash tables which I did on 2011-12-20, whereby negative values coming out of a hashing function would cause code to negatively index before the start of a hash table.

Kaz Kylheku <kkylheku>
Project AdministratorIn charge of this item.
Sat 19 Nov 2011 05:41:19 AM UTC, original submission:

Test case:

After seeing the @", the parser gets confused and the ) which follows later triggers an invalid start condition stack pop in the scanner.

Kaz Kylheku <kkylheku>
Project AdministratorIn charge of this item.


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    Follow 3 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2013-10-10 kkylheku StatusNone => Fixed
        Assigned toNone => kkylheku
        Open/ClosedOpen => Closed

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