Study alternatives to use of auto_index for on-demand compilation

[andreas-kupries]

In mode compile&run Critcl currently populates the auto_index array with the declared commands, so that the standard unknown can trigger the compilation on first use.

Proposed alternatives:

• rkeene : Create Tcl shims which trigger compilation and get replaced with the compilation result.
• dgp : Hook into namespace unknown.

Study feasibility of either.

For background, there is some intent and pressure on the core to remove auto_index.

A first thing to do would be to isolate the code doing the registration (if it is not already).
Then it can be replaced with alternate implementations.

Thoughts:

• The idea of shims is likely the most portable not depending on any specific version of the core, and its features. I.e. namespace unknown is a recent feature we would have to check for before using it.
• The current code is portable across major versions simply because auto_index exists since pretty much the beginning. That breaks should auto_index go away. Plain Tcl procs on the other hand will never go away.

[rkeene]

I added the shim proc in tcc4tcl's basic critcl wrapper here: http://chiselapp.com/user/rkeene/repository/tcc4tcl/artifact?ln=68-85&name=f455727caf579fa7

And it seems to work

[andreas-kupries]

Thank you. Copied into here

    68  proc ::critcl::cproc {command argList resultType body} {
    69  	set handle [::critcl::_allocateHandle]
    71  	set command [::tcc4tcl::lookupNamespace $command]
    73  	$handle cproc $command $argList $resultType $body
    75  	set body {
    76  		set args [uplevel 1 set args]
    78  		::critcl::_go $handle
    81  		tailcall $command {*}$args
    82  	}
    84  	proc $command args [list apply [list {handle command} $body] $handle $command]
    85  }

Regular critcl might be able to work without apply, and tailcall conditionally (8.6+), uplevel otherwise.