How to not fold constants?

[Stephen L Moshier]

> It's not clear from your mail what the C9X standard requires

The C9X rule says, roughly speaking, that float constant expressions
may be folded only if nothing can possibly go wrong.  It goes on to
say that not ever folding at all is an acceptable way to implement
that rule  -- except for the case of static initializations.

So I am asking, how do we figure out that an expression is a
static initializer?