The last tcc release is very old, and tcc has received many fixes and new features since then.
What are the plans for a new release?
I vote for a 0.9.28 rc with the current features, see, what simple fixes are possible and then make a release in the next weeks. (Would help distros to include a recent tcc)
Afterwarde prepare for tcc 1.0 later this year. That would make it possible for distros to add tcc 1.0 in there spring/LTS releases.
Unfortunately, we missed the 20. anniversary for tcc 1.0 (first commit: 27. Oct. 2001), but releasing at the 21. anniversary is still possible.
For 1.0, i vote for fixing more bugs and verified C99 support, either excluding Complex math or with optional Complex math (enable during configure, but defaults 'off')
tcc already understand some C11 features and newer extensions (example: __has_include) but the related implementation is missing or buggy (_Atomic)
I would see fixes for C11 things as 'cool, when working', but optional for tcc 1.0.