[gnugo-devel] cygwin sscanf problem in gtp.c

[Trevor Morris]

Here's a test file that shows how gtp.c fails.
In short, the " %s %n" construct isn't working as expected.  In the
last sscanf, 1 is returned, but n is not set.  This causes very
bad behavior in gtp.c (line 97, etc.) [specifically p += n].
Is this specific to cygwin, or do other platforms have this problem
too?

const char *db = "dragon_data black\n";
const char *d1 = "dragon_data\n";

char command[1024];
int n=-1,r;

dump(const char *s, char*command) {
  printf("%d %d '%s' '%s'\n", r, n, command, s);
  n = -1 ;
}


main() {
  r = sscanf(d1, " %s%n", command, &n);
  dump(d1, command);
  r = sscanf(db, " %s%n", command, &n);
  dump(db, command);
  r = sscanf(d1, " %s%n", command, &n);
  dump(d1, command);

  r = sscanf(d1, " %s %n", command, &n);
  dump(d1, command);
  r = sscanf(db, " %s %n", command, &n);
  dump(db, command);
  r = sscanf(d1, " %s %n", command, &n);
  dump(d1, command);
}

cygwin (gcc) output:
1 11 'dragon_data' 'dragon_data
'
1 11 'dragon_data' 'dragon_data black
'
1 11 'dragon_data' 'dragon_data
'
1 -1 'dragon_data' 'dragon_data
'
1 12 'dragon_data' 'dragon_data black
'
1 -1 'dragon_data' 'dragon_data
'


VC output:
1 11 'dragon_data' 'dragon_data
'
1 11 'dragon_data' 'dragon_data black
'
1 11 'dragon_data' 'dragon_data
'
1 12 'dragon_data' 'dragon_data
'
1 12 'dragon_data' 'dragon_data black
'
1 12 'dragon_data' 'dragon_data
'