Fortran calls to C

[tkhandan]

I am trying to call a C routine from my Fortran main. I am having difficulty in prototyping two arrays, one 1D array and another a 2D array. Following some examples in the Visual Studio (V6.0), I trid declaring as

INTERFACE TO FUNCTION ADD2 [C,ALIAS:'_ADD2'] (a, b)

REAL*4 a [REFERENCE]
REAL*4 b [REFERENCE]
END

where a is 1D array and b is 2D array. I get the compiler error "Error: The shape matching rules of actual arguments and dummy arguments have been violated." Any help would be greatly appreciated.

Thanks,

Khandan

[Jugoslav_Dujic]

You have to specify that a andb are arrays:

INTERFACE

FUNCTION ADD2 (a, b)

!DEC$ATTRIBUTES C, ALIAS: "_ADD2":: ADD2

REAL*4 a(*)

REAL*4 b(*)

END FUNCTION

END INTERFACE

Syntax with brackets and INTERFACE TO is obsolete and not documented (although still supported for compatibility with old MS compilers) -- I suggest using official !DEC$ form.

Matching a 1-d dummy to a 2-d actual argument is allowed for assumed-size arrays. However, note that C function has to know the leading dimension of b somehow -- either as hard-coded or by using an extra argument. Note also that indexing such an array is reversed in Fortran and C, andindexing is also different (starting with 1 in Fortran and 0 in C), e.g.

REAL:: B(10,5)

B(7,3) <-> *(b + (3-1)*10 + (7-1)) <-> b[2][6]

Jugoslav

[tkhandan]

Thnak you Yugoslav.

Your suggestions worked very well. I also have another problem in which I am calling a Fortran code from C where I need to transfer data back and forth via a COMMON BLOCK. I tried creating a C structure with fields corresponding to the common-block variables and declared as "extern struct block_name CBLOCK" as per on line help in V.Studio 6.0. When I step into Fortran, the values are not there. I would greatly appreciate any help with a simple example.

Thank you

Khandan