[Swig-devel] [ swig-Patches-1809819 ] prevent SWIG_Tcl_ConvertPtr from calling the unknown proc

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Patches item #1809819, was opened at 2007-10-08 12:03
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Cliff C (cliff_c)
Assigned to: Nobody/Anonymous (nobody)
Summary: prevent  SWIG_Tcl_ConvertPtr from calling the unknown proc

Initial Comment:
SWIG_Tcl_ConvertPtrFromString is called whenever a std::vector<> is used in an exported function. This is to check whether the object passed is actually a SWIG-owned pointer to a vector. It may be a native list, but the check for a pointer always happens first. 

The pointer check takes the argument and calls it like so: <argument> cget -this. If this fails, it knows it's not a pointer. The bad thing is that, if it's not a pointer, as part of the call to <argument> cget -this, the unknown proc will be called. This proc may be overridden by any Tcl user, and if it is, weird things may happen here.

The fix to this (admittedly obscure) issue is to first check whether <argument> is a command, and _then_ call cget -this on it. 

The change is to tclrun.swg. The new code was added between "/* Hmmm..." and "if (Tcl_VarEval(interp, c,"cget -this"...":

To test, you'd need a .i that uses vector (see the standard examples for that), and to redefine unknown to puts something when it is called (shown here): 

rename unknown unknown_orig
proc unknown {args} {puts "unknown called because of: $args"; uplevel 1 unknown_orig $args} 



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