As I said, I think that basically doing a global search and replace of "undefined" with "implementation-defined" in the standard would be a good first attempt (

As I said, I think that basically doing a global search and replace of "undefined" with "implementation-defined" in the standard would be a good first attempt (this should be possible, because that's how C compilers worked for a long time and – with optimizations turned off – generally still do). This wouldn't solve everything, but it makes the use case for C as a "portable assembler" better, which could then be used as a foundation to build upon.