HP-UX 10.20 has fputs_unlocked in libc.  However, it doesn't
have fputc_unlocked.  GCC appears to optimize a call to
fputs_unlocked with a character count of one to a call to
fputc_unlocked.  This fails on HP-UX 10.20.  Here is a
little test program, "fputc_unlocked.c", which demonstates
the problem:

typedef struct {
  int __cnt;
  unsigned char *__ptr;
  unsigned char *__base;
  unsigned short __flag;
  unsigned char __fileL;
  unsigned char __fileH;
} FILE;

extern FILE __iob[];

extern char *fgets_unlocked(char *, int, FILE *);

int main ()
{
  fputs_unlocked ("\n", (&__iob[1]));
}

516 (hiauly1)dave> /opt/gnu/bin/gcc -o fputc_unlocked fputc_unlocked.c -O1
/usr/ccs/bin/ld: Unsatisfied symbols:
   fputc_unlocked (code)
collect2: ld returned 1 exit status

Release:
gcc 3.2 branch and later

Environment:
hppa1.1-hp-hpux10.20