Author:         Ashok P. Nadkarni <[email protected]>
State:          Draft
Type:           Project
Tcl-Version:    9.1
Tcl-Branch:     tip-702

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Abstract

This TIP proposes to always statically link the registry and dde extensions on Windows.

Rationale

Historically, the registry and dde packages (only available on Windows) have been shipped as separate shared libraries when Tcl is dynamically linked. In the 9.0 default build configuration, the DLL's are stored in the ZipFS archive and then written out to disk before loading. This has the following drawbacks:

• The file system is cluttered with temporary files that are not cleaned up - Ticket.

• Some real-time AV scanners flag programs that write DLL's to disk and load them immediately as malware.

• There is some performance cost associated with the mechanism, though perhaps immaterial in the grand scheme of things.

The above ticket has a proposal to use CRC's to identify the file and prevent file clutter. The exact scheme has not been detailed but any such has the potential to create race conditions. More important, it does not help with the AV flagging.

It is also the case that there is no obvious benefit to keeping the extensions as separate DLL's.

This TIP therefore proposes to always build registry and dde as static packages.

Specification

The nmake and autoconf build systems will be changed to compile and statically link the registry and dde packages as part of the main Tcl library (either shared or static).

The tclreg*.{lib,dll} and tcldde*.{dll,lib} DLL and static libraries will no longer be built.

Applications will still be required to

package require registry
package require dde

to use the package commands. But see Discussion below.

The registry and dde packages will no longer be versioned separately and will instead use the Tcl version. This is primarily because they are always shipped as part of the Tcl core library and a separate version adds unnecessary work to update in at least six different locations.

The Tcl 8.7 compatible DLL's will not be built. Since Tcl 9 will no longer build the DLL's, it serves little purpose to build the ones for Tcl 8.7. Keeping both implementations in the same code base adds unnecessary complexity that will likely never be used.

Discussion

Issue: is the package require really necessary?

My preference is for the registry and dde commands to be always available without the need for a package require. It reduces (albeit marginally) the start up overhead of registering static libraries. However, a small incompatibility would be introduced as applications that never use the registry and dde packages may have their own registry and dde global commands (or from other packages) that would now be in conflict. Personally, I feel the chances of this are low and would prefer the commands always be available. Opinions sought.

Implementation

See the tip-702 branch.

Copyright

This document has been placed in the public domain.