C-- isn't a strict subset of C; it changes a lot, but it takes the idea of a C subset as its starting point and then makes a wide swath of changes as needed. It

C-- isn't a strict subset of C; it changes a lot, but it takes the idea of a C subset as its starting point and then makes a wide swath of changes as needed. It's also designed to be non-portable (apparently to make sure that architecture-dependent optimizations can be performed if necessary), although from my limited experience with the specification I doubt it'd be hard to write semi-portable C-- and modify it as necessary at the loss of some optimizations.