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Description of problem:
Using a main program in C and a subroutine in Fortran, where the Fortran
uses isatty without using any other Fortran I/O, results in a segmentation fault
at that point.

Inserting another Fortran I/O operation before the call to isatty works around
the problem. Alternatively, calling f_init explicitly from the C code before
calling the Fortran also works.

My problem occurs in a large complicated set of code mixing C and Fortran, but
the example below illustrates the problem.

Version-Release number of selected component (if applicable):
gcc-g77-3.2-7

How reproducible:
Always

Steps to Reproduce:
1.Use a C main routine like:
#include <stdio.h>

int main(int argc, char **argv) {
   
   extern a_(int *result);
   int result = 0;
   
   a_(&result);
   printf("result = %d\n", result);
   return(0);
}

2.and a Fortran subroutine like:
      subroutine a(result)
      integer result

      result = 1
      if (isatty(6) .eqv. .true.) result = 2
      return
      end

3. g77 -o mytest mytest.c mytest.for
4. ./mytest
    

Actual Results:  Segmentation fault
Running with g77 -g and gdb:
#0  0x42069ab7 in fileno_unlocked () from /lib/i686/libc.so.6
#1  0x4003c337 in G77_fnum_0 () from /usr/lib/libg2c.so.0
#2  0x4003c6e8 in G77_isatty_0 () from /usr/lib/libg2c.so.0
#3  0x080484e8 in a_ (result=0xbffff454) at mytest.for:5
#4  0x080484af in main (argc=1, argv=0xbffff4a4) at mytest.c:8
#5  0x420158f7 in __libc_start_main () from /lib/i686/libc.so.6


Expected Results:  Should return "result = 1" or "result = 2" depending on
whether output
is redirected or not.

Additional info:

Inserting the line:
f_init();
in the C code prior to calling the function "a_" works around the problem.

Or, inserting the line:
      write(*,'($)')
before the call to isatty in the Fortran also works around the problem, since
write implicitly calls f_init.

It is not a very serious bug, but one which proved rather hard to track down and
I suspect is probably easy to fix, so it would be nice to see it fixed.