Passing Fortran CHAR*(*) to C

[CJason]

I'm using the Intel compiler on Linux.

I'm attempting to pass a Fortran string variable defined as:

CHARACTER*(*) THIS

to a C function. I've passed character strings from Fortran to C MANY times...with no real issues. However, trying to pass a variable declared as above, proves very difficult. NORMALLY, I can get the length of the strings off the last hidden arguments in the C functions. However, when the variable is defined as above, this hidden arguments are proving very unstable (that is, not accurate AT ALL).

Any ideas?

 

[ArkM]

Read this:

http://www.ncsa.illinois.edu/UserInfo/Resources/Software/Intel/Compilers/8.1/f_ug1/pgwchars.htm

May be it helps...

 

[xwb]

Which version of the Intel compiler are you using? Version 10 and 11 support the C interface.

 

[CJason]

Version 11. What do you mean by "support the C interface"? It's true that I've been successfully interfacing Fortran and C with "normally defined" fortran characters (like CHARACTER*10). But, the problem occurs with the CHARACTER*(*) declarations. Any ideas?

 

[xwb]

V11 supports Fortran 2003 which defines a standard interface for C.

To get your C routines to accept Fortran strings, you have to account for the length argument passed along with the string address. For example:

! Fortran code
INTERFACE
   SUBROUTINE usestr (string)
   CHARACTER*(*) string
END INTERFACE

The C routine must expect two arguments

void usestr (
   char *string,
   unsigned int string_len)

Alternatively, if you wish to just use one argument for the C routine, you must null terminate the string in Fortran.