bug with printf positional arguments?

[Jon Turney <jon.turney@dronecode.org.uk>]

The following trivial program (extracted from a glib testcase)

> #include <stdio.h>
> 
> int main()
> {
>   printf ("%1$*2$.*3$s", "abc", 5, 2);
> }

does not produce the expected output of "   ab", on 64-bit Cygwin.

 From a bit of staring at and stepping through get_args() in 
libc/stdio/vfprintf.c, it looks like the problem is (something like) we 
don't have the knowledge that the first positional variadic argument 
should be treated as a pointer, at the point that we store it's value, 
so it gets treated as an integer (the default), which is going to lead 
to truncation on LP64 platforms.

A straightforward way to fix this eludes me.