Question about precise definition FLOOR_MOD_EXPR

[Richard Kenner]

What should the result of <FLOOR_MOD_EXPR 11 -5> be?

There is recent code added to fold that says that the negation can be ignored
so this should be 1.

However, if the "-5" is a variable and you let it be evaluated at runtime,
the result is -4.

I think it's a bad idea that folding produces a different result than
executing the computation at run-time.

Moreover, what *is* the result supposed to be?  The Ada standard is clear
that it should be -4.  From looking at the online version of the C
standard, I can't tell whether 1, -4 or choosing either at random is
a valid result.  Does anybody know?  How about C++?  Java?  Does this
come up in Fortran?