Re: [PATCH] stdio: fix probe on mingw under gcc 5.1

[Paul Eggert]

$EGREP has undefined behavior on binary data, so this isn't portable.

I long ago gave up on AC_EGREP_CPP, since it's too flaky nowadays.  Why can't we 
test directly for what we're worried about?  I'm afraid I am not following why 
the value of PRIdMAX is related to whether printf should use the __gnu_printf__ 
or the __printf__ attribute.

By "test directly" I mean compile a little test program with printf and see 
whether GCC warns about misuse.  By seeing what GCC warns about and what it 
doesn't we should be able to figure out which attribute is appropriate.