[Bug c/71870] wrong location of "%n$" directive in -Wformat

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71870

Eric Gallager <egallager at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2017-07-30
                 CC|                            |egallager at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #2 from Eric Gallager <egallager at gcc dot gnu.org> ---
Confirmed. Note that the original testcase now prints an additional
-Wformat-overflow warning:

$ /usr/local/bin/gcc -c -Wall -Wextra -Wpedantic -S 71870.c
71870.c: In function ‘f’:
71870.c:5:26: warning: unknown conversion type character ‘r’ in format
[-Wformat=]
  __builtin_sprintf (d, "%r");
                          ^
71870.c:7:2: warning: ISO C does not support %n$ operand number formats
[-Wformat=]
  __builtin_sprintf (d, "%2$i%1$i", 1, 234);
  ^~~~~~~~~~~~~~~~~
71870.c:7:33: warning: ‘__builtin_sprintf’ writing a terminating nul past the
end of the destination [-Wformat-overflow=]
  __builtin_sprintf (d, "%2$i%1$i", 1, 234);
                                 ^
71870.c:7:2: note: ‘__builtin_sprintf’ output 5 bytes into a destination of
size 4
  __builtin_sprintf (d, "%2$i%1$i", 1, 234);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
$