A bytecode format, like what CUDA, Metal Compute and DirectX Compute use.

Which Khronos finally adopted as SPIR, but the drivers aren't there yet.

Regarding the other Khronos APIs, a C API is like being stuck in a PDP-11 world.

Many mix the idea of C API with OS ABI, it only happens to be the same if the OS APIs are exposed as plain C.

There many cases where this isn't like it, e.g. mainframes, mobile OSes, and most userspace on OS X (Obj-C runtime) and Windows (.NET and COM).