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Re: Internal procedure not allowed as actual argument

Janus Weil wrote: 
Hi all,
I have a question: why doesn't gfortran allow passing an internal
procedure as an argument to another procedure, as in this example:


subroutine sub

 call proc(f1)
 call proc(f2)

contains

 real function f1(x)
 ...
 end function f1

end subroutine sub


real function f2(x)
...
end function f2


If we have a subroutine "proc" that expects an external function as
its argument, "call proc(f2)" is allowed by gfortran, while "call
proc(f1)" triggers an error like this:

Error: Internal procedure 'f1' is not allowed as an actual argument at (1)

g95 shows the same behaviour, but ifort doesn't complain about this at all.
Can anyone tell me what the reason for this restriction is?

Quoting 12.4.1.3. from the F2K draft standard:

"If a dummy argument is a dummy procedure without the POINTER attribute, the associated actual argument shall be the specific name of an external, module, dummy, or intrinsic procedure, an associated procedure pointer, or a reference to a function that returns an associated procedure pointer. The only intrinsic procedures permitted are those listed in 13.6 and not marked with a bullet (•). If the specific name is also a generic name, only the specific procedure is associated with the dummy argument."

Note that internal procedures are not mentioned. The idea behind this is that it is hard to make the local variables of the containing procedure visible to the contained procedure when it's called from somewhere else.

Cheers,
- Tobi

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