how to give more than one c file as input to GNU Cflow?

I was able to generate the callgraph of one file using gnu – cflow, but I was not able to find out how to generate the call graph for multiple files using cflow.

I tried following

• cflow test.c,hello.c

  It generates the callgraph for test.c and not creating it for hello.c

• cflow test.c hello.c

  It generates the callgraph for hello.c and not creating it for test.c

I don’t know how to pass multiple files to cflow.

Any idea about this?

hello.c

int
 who_am_i (void)
 {
     struct passwd *pw;
     char *user = NULL;

     pw = getpwuid (geteuid ());
     if (pw)
     user = pw->pw_name;
     else if ((user = getenv ("USER")) == NULL)
     {
         fprintf (stderr, "I don't know!n");
         return 1;
     }
     printf ("%sn", user);
     unused_function();
     return 0;
 }

 int
 main (int argc, char **argv)
 {
     if (argc > 1)
     {
         fprintf (stderr, "usage: whoamin");
         return 1;
     }
     return who_am_i ();
 }
 void unused_function()
 {
     printf();
     error1();
     printf();
 }
 void error1()
 {
     error2();
 }
 void error2()
 {

 }

test.c

int tests()
{ return 0;}

Answer

• cflow test.c hello.c

Actually above statement is correct and tests() does not show up in callgraph, because it is never called.

answer given by @AndreasGrapentin