El dom, 6 dic 2020 a las 10:09, ToddAndMargo via perl6-users (<
perl6-us...@perl.org>) escribió:
> On 12/4/20 8:55 PM, ToddAndMargo via perl6-users wrote:
> > On 2020-12-04 20:28, Curt Tilmes wrote:
> >> On Fri, Dec 4, 2020 at 10:52 PM ToddAndMargo via perl6-users
> >> <perl6-us...@perl.org> wrote:
> >>
> >>> This is the C way, although it shows deleted printers as well:
> >>>
> >>> #include <iostream>
> >>> #include <cups/cups.h>
> >>>
> >>> int main() {
> >>> cups_dest_t* dests;
> >>> int nCount = cupsGetDests2(CUPS_HTTP_DEFAULT, &dests);
> >>>
> >>> for (int i = 0; i < nCount; i++) {
> >>> cups_dest_t dest = dests[i];
> >>> std::cout << dest.name << std::endl;
> >>> }
> >>> }
> >>
> >> Roughly translating that into Raku Nativecall (my system has
> >> cupsGetDests(), but not cupsGetDests2() -- you'll have to update to
> >> that)
> >>
> >> use NativeCall;
> >> class CupsDest is repr('CStruct') {
> >> has Str $.name; # This is the first field in the struct --
> >> add more if you need them
> >> }
> >>
> >> sub cupsGetDests(Pointer is rw --> int32) is native('cups') {}
> >>
> >> my $ptr = Pointer.new;
> >> my $nCount = cupsGetDests($ptr);
> >>
> >> for ^$nCount -> $i {
> >> my $dest = nativecast(CupsDest, Pointer.new($ptr + $i *
> >> nativesizeof(Pointer)));
> >> say $dest.name;
> >> }
> >>
> >
> >
> >
> > Hi Curt,
> >
> > What am I doing wrong?
> >
> > #!/usr/bin/env raku
> >
> > use NativeCall;
> > class CupsDest is repr('CStruct') {
> > has Str $.name; # This is the first field in the struct --
> > add more if you need them
> > }
> >
> > sub cupsGetDests(Pointer is rw --> int32) is native('cups') {}
> >
> > my $ptr = Pointer.new;
> > my $nCount = cupsGetDests($ptr);
> >
> > for ^$nCount -> $i {
> > my $dest = nativecast(CupsDest, Pointer.new($ptr + $i *
> > nativesizeof(Pointer)));
> > say $dest.name;
> > }
> >
> > $ ListPrinters.pl6
> > Cannot locate native library 'libcups.so': libcups.so: cannot open
> > shared object file: No such file or directory
> > in method setup at
> >
> /opt/rakudo-pkg/share/perl6/core/sources/947BDAB9F96E0E5FCCB383124F923A6BF6F8D76B
>
> > (NativeCall) line 298
> > in block cupsGetDests at
> >
> /opt/rakudo-pkg/share/perl6/core/sources/947BDAB9F96E0E5FCCB383124F923A6BF6F8D76B
>
> > (NativeCall) line 587
> >
> >
> > $ locate libcups.so
> > /usr/lib/libcups.so.2
> > /usr/lib64/libcups.so.2
> >
> >
> > -T
>
> I did the following:
>
> # cd /usr/lib
> # gls libcups
> libcupsimage.so.2
> libcups.so.2
>
> # ln -s libcups.so.2 libcups.so
>
Why did you do so? ;-)
# ls -al libcups*
> -rwxr-xr-x. 1 root root 14612 Nov 10 06:07 libcupsimage.so.2
> lrwxrwxrwx. 1 root root 12 Dec 6 01:03 libcups.so -> libcups.so.2
> -rwxr-xr-x. 1 root root 710236 Nov 10 06:07 libcups.so.2
>
> # cd /usr/lib64
> # ln -s libcups.so.2 libcups.so
> # ls -al libcups*
> lrwxrwxrwx. 1 root root 23 Nov 23 22:09 libcupsfilters.so.1 ->
> libcupsfilters.so.1.0.0
> -rwxr-xr-x. 1 root root 264440 Nov 23 22:09 libcupsfilters.so.1.0.0
> -rwxr-xr-x. 1 root root 15256 Nov 10 06:08 libcupsimage.so.2
> lrwxrwxrwx. 1 root root 12 Dec 6 01:04 libcups.so -> libcups.so.2
> -rwxr-xr-x. 1 root root 686128 Nov 10 06:08 libcups.so.2
>
>
> Running the program now gives:
>
> $ ListPrinters.pl6
> B4350
> (Str)
> Segmentation fault (core dumped)
>
Well, the second $dest clearly has no value in "name". And in the next one
you are getting into a loop and casting pointers and stuff without actually
checking if they're good. It looks like it's pointing nowhere; either the
size is off, or there's any other problem.
Cheers
JJ
--
JJ
