[Tcl-bugs] [ tcl-Bugs-405769 ] rare segfault at "unset -nocomplain"

[nobody <no...@so...>]

Bugs #405769, was updated on 2001-03-03 19:46
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Category: Variables
Group: 8.4a2
Status: Open
Priority: 7
Submitted By: miguel sofer
Assigned to: Donal K. Fellows
Summary: rare segfault at "unset -nocomplain"

Initial Comment:
The command
   unset -nocomplain
(with no further arguments) causes Tcl_UnsetObjCmd (in
tclVar.c) to request the string representation of an
object which was *not* passed as an argument. 

Under special circumstances (which I couldn't trigger
in current sources) this causes a segfault. In order to
cause a segfault,   
    *(stackPtr(stackTop+1)->bytes)
must be in a forbidden memory region at the moment of
the invocation of "unset -nocomplain".

The cure seems pretty harmless: remove the offending
line, which is unused anyway. The offending statement
(line 2627 in tclVar.c) reads:
     name = TclGetString(objv[i]);

Thusly corrected sources pass all tcltests.



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Comment By: miguel sofer
Date: 2001-03-03 20:10

Message:
Logged In: YES 
user_id=148712

Forgot a detail: this also cures the following behaviour,
which is not in agreement with the man page for unset (and
hence is a bug):

[mig@ant bin2]$ tclsh8.4 
% set -- 1
1
% unset -nocomplain --
% set --
1



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