On Sep 27, 2006, at 12:35 PM, Steve Kargl wrote:
The author of g77 made the decide to use the f2c runtime library.
f2c always promotes a single precision function to double
precision.
I don't see an obvious way to do that and still conform to the Fortran
standard. Perhaps I am missing a trick. Or perhaps g77 just fails to
conform to the Fortran standard there. Having a compiler switch to
enable a nonconforming behavior is one thing. But having a compiler
that did not even have the option to conform to the standard strikes me
as.... um.... problematic.
The nonconformance might not show up in most codes, but it sure isn't
hard to come up with a case of valid Fortran code that would fail under
such an implementation. Consider
call sub(f(x))
where f(x) returns a (single precision) real, and sub has a (single
precision) real dummy argument. If f(x) is implemented to return a
double instead of a single, then its result isn't going to be valid as
an actual argument for sub. But if sub is separately compiled, there
won't be an opportunity for the compiler to detect or fix the problem.
Perhaps I'm misunderstanding what was going on here, but I'm at least a
little suspicious that you've just described a way in which g77
violates the standard (which is different from extending it).