[jcranmer]

So the things you mention aren't useful for getting consistent numerical results. You really have to start getting into obscure platforms like mainframes to find stuff where float and double aren't IEEE 754 single and double precision, respectively. FLT_EVAL_METHOD is largely only relevant if you're working on 32-bit x86 code, and even then, you can sidestep those problems if you're willing to require that hardware be newer than 20 years old or so.

The actual thing you need to do for consistency is to be extremely vigilant in the command line options you use, and also bring your own math library implementations rather than using the standard library. You also need vigilance in your dependencies, for somebody deciding to enable denormal flushing screws everybody in the same process.