CALL decc$bsearch from FORTRAN

[Michael Menge]

VMS 8.3 FORTRAN X8.0n
In a Fortran application I call the C-routine decc$bsearch using the HP specific POINTER statement: POINTER (pointer,pointee) (ex. test_bsearch1.for, o.k.).
Another way is to use an interface block to define the function and its parameter (ex. test_bsearch2.for). Example 2 runs with accvio and I think some dummy parameters are not defined correctly. You can see the correct C-format of the interface block with
$ help crtl bsearch.

An interface block in Fortran is type specific I think, there is no "void" pointer as in C. What is to do if you want to call decc$bsearch twice in a routine with different table-types and keys? With the Pointer statement as in example 1 it's easy, but using interface blocks, do I have to write two special routines with different interface blocks each?

[Hoff]

Probably not the answer you want...

Do you need to call the innards of a C standard library function directly from Fortran?

Under the theory of "if it hurts, don't do it", I'd tend to either jacket the code with C code that has tailored the underlying interface to meet Fortran norms, or move to the lib$ tree-related calls, including:

LIB$INSERT_TREE, LIB$LOOKUP_TREE, LIB$TRAVERSE_TREE_64, etc.

I personally find that arbitrary API jacketing is easier in C than in Fortran.

And if this is a case of not using C, you can also use a Macro32 jacket. Or the LIB$ RTL calls.

Rules for pointees (which you've probably already found) are here:

http://h71000.www7.hp.com/DOC/82final/6324/6324pro_060.html#df_pointer_stmt

[John Gillings]

Michael,

If you want your arguments type checked, and have different types, then you'll need to distinguish between different instances of the routine. FORTRAN doesn't do polymorphism very well.

I don't have a compiler handy to check, but it's possible the function name doesn't need to be the same as the C function name. So this might work:

INTERFACE
FUNCTION decc$bsearch_TYPE1 (key, tab, tabSize, elemSize, cmpFunc)
USE keyidx
IMPLICIT NONE
!DEC$ ATTRIBUTES C :: decc$bsearch
...
END INTERFACE

INTERFACE
FUNCTION decc$bsearch_TYPE2 (key, tab, tabSize, elemSize, cmpFunc)
USE keyidx
IMPLICIT NONE
!DEC$ ATTRIBUTES C :: decc$bsearch
...
END INTERFACE

if not you can implement a simple jacket routine. Hoff finds C easier, but I think MACRO32 is the easiest of all:

.title DECC$BSEARCH_JACKETS
.psect $code,rd,nowrt,exe
.CALL_ENTRY LABEL=decc$bsearch_type1,MAX_ARGS=5,HOME_ARGS=TRUE
CALLG (AP),G^DECC$BSEARCH
RET
.CALL_ENTRY LABEL=decc$bsearch_type2,MAX_ARGS=5,HOME_ARGS=TRUE
CALLG (AP),G^DECC$BSEARCH
RET
.END

On the other hand, if you use a builtin function on your argument %VAL, %REF you disable type checking for that argument. So, using a builtin when you don't actually need to will make that argument polymorphic (but the compiler won't help spot your bugs)