Top 3 C Type System Projects

datatype99

29 794 3.5 C

Algebraic data types for C99
interface99

15 262 1.9 C

Full-featured interfaces for C99
InfluxDB

www.influxdata.com sponsored

Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
libGimbal

3 60 8.8 C

C17-based extended standard library, cross-language type system, and unit testing framework targeting Sega Dreamcast, Sony PSP and PSVita, Windows, Mac, Linux, Android, iOS, and WebAssembly.

Project mention: Object-oriented Programming with ANSI-C [pdf] | news.ycombinator.com | 2023-06-21

I'm a huge academic fan of what GTk has accomplished (thanks to their GObject type system), and as much as I know the C89 crowd who thinks macros are all evil probably abhor this kind of thing, I think GTk is one of the most epic, impressive, ambitious C codebases in existence. Witness as non-OO C matches, rivals, and quite often beats Qt on equivalent classes/features in plain C... It's even above "just C++ style C," as they have added features like a property and signal system...
Such a fanboy it inspired my own type system and massive core library, libgimbal, which uses a type system similar to GObject and targets game consoles like the Sega Dreamcast: https://github.com/gyrovorbis/libgimbal

NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020).