Package system Tcl-files into `openroad` binary, that it can easily be used standalone

[hzeller]

Right now, the bazel build of openroad has all the relevant tcl system files (e.g. init.tcl, but also timezone data) packaged as runfiles. This has multiple issues

• Without intervention, this just works if openroad is called from within the bazel workspace. If it is copied outside, the user has to figure out a way to assemble the TCL_LIBRARY path. This makes it hard to just distribute a openroad binary.
• The single files in the runfiles require a symlink-tree for each of the uses (e.g. each test that uses the openroad binary) (see bazel: trim tcl_lang runfiles to reduce test symlinks by 58% #9973 )

Tcl already has a way to solve all this: package all these files together and use that via a virtual filesystem, then embed this collection into the final binary. There are multiple ways of doing that, needs to be explored. This entails

• Switching to Tcl 9. There the virtual filesystem has been a stable part of the standard distribution (first, the code needs to be fixed to work with tcl9; working on it in Use Tcl_Size for all tcl functions returning sizes. OpenSTA#323 and Use Tcl_Size for all tcl functions returning sizes. #9979 )
• Use rules_pkg to pack all relevant files togeher (I suggest also including the tclreadline scripts)
• Put this in the binary (various ways to do that: explore)

Result: a binary that is independent, can be copied anywhere and provides the full functionality. Also possibly faster to use in unit tests.

cc: @oharboe

[oharboe]

👍

It sounds like we're moving in the direction of setting more well bounded expectations for the user and this will lead to less disappointment.

OpenROAD executes Tcl but it is framework inverted, it is not a package that you import into your favorite Tcl. It is a walled of version of Tcl with enough functionality to be compatible with the existing use-cases, it is not real Tcl, you can't and shouldn't try to import packages.

If you need to import OpenROAD into a scripting language, use Python and import OpenROAD into your preferred Python installation.

[hzeller]

Tcl is not inverted, it actually is meant to be like that: you have a binary and provide scripting functionality with it. Tool Command Language. Meant to work right out of the box.

Python loading libs is another way some users might like (I am not one those users, as it involves Python :) ).

[oharboe]

Tcl and Python works both ways: you can embed Python/Tcl and be the interpreter or you can be a package that is imported to Tcl/Python.

OpenROAD used to have an embedded Python, but that is not what people have in mind when they say "Python support".

[oharboe]

I love Tcl for its consistent everything is a string paradigm and how small it is. I used jimtcl in embedded systems with hundreds of kbytes of RAM :-)

If I have megabytes, Python starts to become much more attractive.

[maliberty]

Beauty is in the eye of the beholder, I loath tcl and its everything is a string paradigm. I would love to be rid of it. I like Python and Henner doesn't. 🤷

[oharboe]

Languages are dead, all there is left is intent expressed in some form and preferred views of individuals and use cases.

[oharboe]

So maybe time to make Hermetic DSL Python: a subset without package support entirely in C++ with zero dependencies adequate for bazel build scripting and unittests?

A clearly defined restricted subset of features being the main feature.

Starlark did this...

Strangely, unittesting and mockkng is hard, or I have not seen it, in Starlark.

[maliberty]

"programming is solved problem" and other hype fail when you actually use the tools and see their limits. They are impressive but not eliminating humans at this point.

[oharboe]

True. Asymptotically approaching the three things it cant take away from me: Biking to work, drinking coffee and hooking up an oscilloscope.

[hzeller]

This is not a Python vs. Tcl discussion (I don't like any of these).

The topic is to have a openroad binary that does not need tons of symlinks and also works anywhere.

[oharboe]

Indeed, it is about dependencies, robustness and fast turnaround times, to my mind. I think a DSL hermetic Python for bazel scripting could be part of the answer: didnt google it... Surely it has been tried? ons. 1. apr. 2026, 16:59 skrev Henner Zeller ***@***.***>:

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