-Os & inlining functions used only once

[Joe Buck]

> Perhaps it could make sense to add a warning (not enabled through either -W
> or -Wall) which would warn if a static function used only once was not
> marked inline.

Or the user can compile twice, and the first compile writes a side file
that is read the second time.  That approach can be extended to allow
for optimizations across compilation units (the canonical C++ example
is to notice which virtual functions are never overriden by derived
classes, permitting direct calls or inlined calls rather than calls
through the vtable).