Todd.p6

#!/usr/bin/perl6

#`{
   Note: Fedora need the following for NativeCall to work:
       # ln /usr/lib64/libX11.so.6 /usr/lib64/libX11.so
       # ln /usr/lib/libX11.so.6 /usr/lib/libX11.so

https://rt.perl.org/Search/Simple.html?q=nativecall any of these bugs yours?
<samcv> if they are not, then send the bug report by email to rakudobug@perl.org

paste over at http://vpaste.net

https://linux.die.net/man/3/xfetchbytes
https://www.cs.bham.ac.uk/research/projects/poplog/doc/popxref/XBuffers

Str:D means a "defined" string.  Str:U means "undefined"
https://docs.perl6.org/language/nativecall#Passing_and_Returning_Values
}

use NativeCall;


# char *XDisplayName(char *string);
sub XDisplayName(Str:D $name) is native('X11') returns Str { * };

# char *XFetchBytes(Display *display, int *nbytes_return)
sub XFetchBytes(Pointer $display, int32 $length) is native('X11') returns Str { * };

# XStoreBytes(displayptr, string, numbytes)
sub XStoreBytes(Str:D $display, Str:D $str, int32:D $len) is native('X11') { * }

#Display *XOpenDisplay(char *display_name);
sub XOpenDisplay(Str:D $display_name) is native('X11') returns Pointer { * }

my Str $Display;
my $NullStr; # Do not initialize this guy!
$Display = XDisplayName( $NullStr );
my Pointer $displayptr = XOpenDisplay($Display);

print "\$Display = <$Display> \$displayptr = $displayptr.gist()\n";
#XFetchBytes($displayptr, 2).say; crashes

#1 change; before #1  4 seconds ago