[Tcl-bugs] [ tcl-Bugs-219145 ] traces on nonexistent variables

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Bugs item #219145, was opened at 2000-10-25 22:02
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Category: 07. Variables
Group: = 8.0.3
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Kevin B KENNY (kennykb)
Summary: traces on nonexistent variables

Initial Comment:
OriginalBugID: 875 RFE
Version: 8.0.3
SubmitDate: '1998-11-25'
LastModified: '2000-02-22'
Severity: LOW
Status: Assigned
Submitter: pat
ChangedBy: hobbs
RelatedBugIDs: 752 4213
OS: All
FixedDate: '2000-10-25'
FixedInVersion: NA
ClosedDate: '2000-10-25'


This is another problem pointed out by Kevin Kenny in his Tcl/Tk
Conference paper.

Tcl and Tk are missing several pieces of introspection that are
meeting to find memory leaks.  Right now there are no Tcl commands
that can be invoked to find out about traces on nonexistent variables

Something like 'trace vunknown'. 
-- 02/22/2000 hobbs

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>Comment By: Jeffrey Hobbs (hobbs)
Date: 2003-01-17 19:07

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I believe Kevin's point in this is that there is no ability to do a 
trace for the creation of unknown named vars, to see when 
they come into existence.  This would be for either the perl 
behavior of default any non-preexistent var to "" or 0, or in a 
debugging context to trap errors.

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Comment By: Joe English (jenglish)
Date: 2003-01-17 19:00

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[trace vinfo] works on nonexistant variables:

  % trace variable a w someProc
  % trace vinfo a
  {w someProc}
  % info exists a
  0

This works as far back as Tcl 7.4.

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Comment By: Don Porter (dgp)
Date: 2002-07-05 13:55

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1) Is this still correct?

2) Should there be a FR to fill in the missing introspection?

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