Question

I have one question with mixing C-string and fortran-string in one file.

Supposed I am playing with the name string with fixed length 9, I define a length Macro like

#define NAME_LEN 9

in a .c file.

There is an existing fortran-function, let’s name it fortran_function(char* name)

Now I have to call this fortran function in a c function, let’s name is

c_function(char name[]) {

   fortran_function(name)

}

Now the problem is, how should I declare the c_function signature?

c_function(char name[])
c_function(char name[NAME_LEN +1])

or

c_function(char name[NAME_LEN])

Under what situations, I should use 9 as name length or 10?

My understanding is that, as long as you passed a null-terminated string with 9 characters to the c_function, all the declaration are correct. Is that right?

Any other concern should be put here? Any potential bugs?

Answer 1

There’s one more gotcha here, if I remember correctly. Fortran does not use null-terminated strings; instead, it pads the right end of the buffer with 0x20 (space). So, if you have access to the Fortran source, I would modify the function signature to take the length of the passed-in string as an argument. Otherwise, you will probably crash the Fortran side of the code.