Re: [Libguestfs] [nbdkit PATCH 0/2] bind .zero to more languages

On 01/24/2017 09:16 AM, Richard W.M. Jones wrote: > In Perl, old code to raise an error would look like: > > sub pread > { > my $h = shift; > my $count = shift; > my $offset = shift; > my $ret; > read ($FH, $ret, $count, $offset) || die "read: $!" > return $ret; > } > > (Note that die does not exit the program, it raises an exception which > is caught and turned into nbdkit_error in the Perl nbdkit plugin). > > This would continue to work fine, but new code which cared about the > errno could do this instead: > > sub pread > { > my $h = shift; > my $count = shift; > my $offset = shift; > my $ret; > read ($FH, $ret, $count, $offset) || { > nbdkit_set_errno (POSIX::errno ()); > die "read: $!" > } > return $ret; > } Except I can't even figure out how to expose nbdkit_set_error (hmm, I named it set_error instead of set_errno in my v2 series) to the perl code.

In fact, with just this change to example.pl: diff --git i/plugins/perl/example.pl w/plugins/perl/example.pl index fcdac33..64f6de3 100644 --- i/plugins/perl/example.pl +++ w/plugins/perl/example.pl @@ -1,4 +1,5 @@ use strict; +use POSIX (); # Example Perl plugin. # @@ -80,6 +81,8 @@ sub pwrite my $buf = shift; my $count = length ($buf); my $offset = shift; + my $err = POSIX::EPERM; substr ($disk, $offset, $count) = $buf; + die "forced write failure"; } I'm getting this failure: $ ./src/nbdkit -e foo -fv plugins/perl/.libs/nbdkit-perl-plugin.so \ script=plugins/perl/example.pl nbdkit: debug: registering plugins/perl/.libs/nbdkit-perl-plugin.so nbdkit: debug: registered plugins/perl/.libs/nbdkit-perl-plugin.so (name perl) nbdkit: debug: plugins/perl/.libs/nbdkit-perl-plugin.so: load nbdkit: debug: plugins/perl/.libs/nbdkit-perl-plugin.so: config key=script, value=plugins/perl/example.pl Can't load module Fcntl, dynamic loading not available in this perl. (You may need to build a new perl executable which either supports dynamic loading or has the Fcntl module statically linked into it.) at /usr/lib64/perl5/POSIX.pm line 17. Compilation failed in require at /usr/lib64/perl5/POSIX.pm line 17. BEGIN failed--compilation aborted at /usr/lib64/perl5/POSIX.pm line 17. Compilation failed in require at plugins/perl/example.pl line 2. BEGIN failed--compilation aborted at plugins/perl/example.pl line 2. nbdkit: error: plugins/perl/example.pl: one of the required callbacks 'open', 'get_size' or 'pread' is not defined by this Perl script. nbdkit requires these callbacks. So I'm not sure how anyone else is doing anything fancy in an NBD perl script.