topic Passing array of strings to Fortran in Intel® Fortran Compiler

Passing array of strings to Fortran

Martin__Paul — Thu, 07 Apr 2011 17:17:54 GMT

I am calling a 3rd party Fortran DLL from C. The manual describes a function whose argument include: character units(*)*(*)

This I understand refers to a variable-length array of strings.

In this situation does Fortran expect a string length argument for each of the strings in the array? If so should the length arguments be passed individually or also in an array?

Thanks in adv.

Passing array of strings to Fortran

Steven_L_Intel1 — Thu, 07 Apr 2011 17:42:46 GMT

Not "variable length" - what you have here is an array of strings all the same length. What would be passed is the starting address of the strings and, as a "hidden" parameter after all the explicit arguments, the string length passed by value (and of type size_t, not int!) I'm not immediately certain how you would declare such a thing in C - it is not the same as an array of strings in C which is actually an array of pointers.

Passing array of strings to Fortran

Martin__Paul — Thu, 07 Apr 2011 17:53:26 GMT

Thanks. The problem is the library I am calling from C is 3rd party so I can't change its interface. I've tried all the standard things like C-style arrays but as you point out this is not of the same type. Any suggestions gratefully received!

Passing array of strings to Fortran

Steven_L_Intel1 — Thu, 07 Apr 2011 18:06:36 GMT

I was not suggesting you change the third-party interface. I was explaining how you would call this from C. In the simple case of a single argument that is this CHARACTER(*)(*) array, it would be something like:

fsub(char * string, size_t string_len)

where "string" is a series of fixed-length strings (not nul-terminated). Perhaps you can declare it as something like:

char[40][10]

assuming 10 elements of 40 characters each, but my C is rusty enough that I am not sure - this itself may end up as an array of pointers which you don't want. Maybe char[40*10] and fill it in as needed.

Passing array of strings to Fortran

Martin__Paul — Fri, 08 Apr 2011 19:38:29 GMT

The second suggestion worked - indeed the point about char[][] resolving to an array of pointers was correct. As it turned out the library expects strings up to length 8 characters, so I was able to pass a single char* containing the individual string components, e.g.:

char[] = "aaa bbb ccc ddd eee fff ";

This worked - thank you for the swift replies.