[Bug middle-end/49905] Better sanity checking on sprintf src & dest to produce warning for dodgy code ?

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49905

--- Comment #9 from David Binderman <dcb314 at hotmail dot com> ---
I tried a build of the gcc fortran compiler and I found this warning:

../../../src/trunk/libgfortran/intrinsics/date_and_time.c:173:33: warning:
‘%+03d’ directive output truncated while writing ‘9’ bytes into a region of
size ‘6’ [-Wformat-length=]

Source code is

    snprintf (zone, ZONE_LEN + 1, "%+03d%02d",
          values[3] / 60, abs (values[3] % 60));

and

#define ZONE_LEN 5

  char zone[ZONE_LEN + 1];

While it is clear that the region size of 6 is fine, I can't see where the
value 
of 9 bytes is coming from.