[actually on the Cforall team] This is basically our pitch -- the last 30 years of language design features applied to a language that is not only source-compatible with C (like C++), but actually maintains the procedural paradigm of C (unlike C++) -- idiomatic C code should require minimal to no change to make it idiomatic Cforall code, and skilled C programmers should be able to learn the extension features orthogonally, rather than needing to figure out complex interactions between, say, templates and class inheritance. We are working in the same space as C++, and do draw inspiration from C++ where useful, but with the benefit of decades of watching C++ try things to see where the important features are.
There's also some really neat language-level concurrency support; work is ongoing on new features and a shorter summary, but you can see one of our Master's student theses for details: https://uwspace.uwaterloo.ca/handle/10012/12888
the existence of exceptions seems to bely the idea of minimal changes to make idiomatic C code idiomatic Cforall code.
While C does have longjmp and friends, usage of them is hardly idiomatic, so most C code assumes no non-local tranfer of control happens when calling functions. Coding with non-local transfer of control and without require very different idioms.
There's also some really neat language-level concurrency support; work is ongoing on new features and a shorter summary, but you can see one of our Master's student theses for details: https://uwspace.uwaterloo.ca/handle/10012/12888