The C Star (C*) language from the selfie project also does not support structs, yet in 12KLOC of code they implemented a C Star compiler that can compile selfie (and outputs ELF files), an emulator that runs RISC-U (RISC-V subset), and a hypervisor.

There was also Small-C[1], which initially only did integers, characters and simple arrays. Formed the basis for quite a few derivates.

[1]: https://en.wikipedia.org/wiki/Small-C