Compiling ANSI C on non-ANSI C environment

[Dave Jones]

The topic under consideration is a compiler from ANSI-C to
original C, ("C Classic"?), for those of us who have UNIX boxes
with C, but not the ANSI extensions and changes -- Sun workstations
in my case. I'm seeing more and more stuff on the net in ANSI-C, which
I cannot use easily, and it would be nice to have some of the features
for development work also, particularly prototypes.

So, what exactly are the tricky bits?

I mentioned passing floats (not doubles) to procedures. Ditto chars.
Raymond Chen reminded me of the ANSI rule against rearranging
floating-point expressions.

What else?