snprintf (d, sizeof (d), fmt, dir, fname);
snprintf (d, l, fmt, dir, fname);
char *mutt_concat_path (char *d, const char *dir, const char *fname, size_t l){  const char *fmt = "%s/%s";    if (!*fname || (*dir && dir[strlen(dir)-1] == '/'))    fmt = "%s%s";    snprintf (d, sizeof (d), fmt, dir, fname);  return d;}