Tcl Source Code

The patch insures that there are always valid
iPtr->varFramePtr and iPtr->framePtr, even at root
level. This simplifies the code as the checks for
iPtr->varFramePtr==NULL are not needed anymore.

It also adds new functionality (currently unused): core
calls to Tcl_EvalObjv with TCL_EVAL_INVOKE may set a
namespace in which the command lookup is to be
performed; if none is requested, the lookup is done at
global level as before.

The patch hijacks two unused fields from the Interp struct:

-    char *unused3; /* No longer used (was errorInfo) */
-    char *unused4; /* No longer used (was errorCode) */
+    CallFrame *rootFramePtr; /* Global frame pointer
for this interpreter */
+    Namespace *lookupNsPtr;  /* Namespace to use ONLY
on the next
+                              * TCL_EVAL_INVOKE call
to Tcl_EvalObjv */

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Possible alternative implementation of the ns lookup
feature: add a flag value TCL_EVAL_IN_NAMESPACE that causes
TEOV and TEOVI to interpret objv[0] as a namespace name for
lookup? May be cleaner, and easier to expose to extensions.

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The tying-in to TCL_EVAL_INVOKE is just an attempt to
minimize the scope of the patch to where it is needed for
enabling 1577492, 1577324 and 1577282. It is trivial to
avoid tying it in by just using iPtr->lookupNsPtr!=NULL as
the signal to use this, as long as TCL_EVAL_GLOBAL is not
passed.

I do not remember what the problem is with the TEI flag. If
it is just the fact that it is a flag that is publicly
exposed but not meant to be used outside the core, this also
would enable its complete removal: again, let
iPtr->lookupNsPtr!=NULL be the way to signal that the TEI
behaviour is wanted, with the current behaviour triggered by
iPtr->lookupNsPtr==iPtr->globalNsPtr

I am somewhat confident that this does not stand in the way
of a fix of the TEI issue, even without knowing what the
issue actually is. 

One possible way to explode it: let the current behavior of
TEI be separated in:

* run in global: set iPtr->lookupNsPtr=iPtr->globalNsPtr
* do not trace errors: rename TEI to TCL_EVAL_NO_ERROR, and
let it mean just that
* do not reset ensemble flags: a new flag value? Or keep it
tied to the "run in global" behaviour?

Note that TEI is currently exposed in tcl.h but not
documented in the man pages, so it is a valid question if
any extension is actually using it.

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One possible wrinkle here
is that we should really
be doing away with, or at
least "exploding" the
TCL_EVAL_INVOKE flag, if
it's the one I suspect it is.

This feature might well
be suitable for one of
its successors.

File Added - 198168: varframe.patch