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    use Devel::CheckLib;

    check_lib_or_exit( lib => 'jpeg', header => 'jpeglib.h' );
    check_lib_or_exit( lib => [ 'iconv', 'jpeg' ] );
  
    # or prompt for path to library and then do this:
    check_lib_or_exit( lib => 'jpeg', libpath => $additional_path );

=head1 USING IT IN Makefile.PL or Build.PL

If you want to use this from Makefile.PL or Build.PL, do
not simply copy the module into your distribution as this may cause
problems when PAUSE and search.cpan.org index the distro.  Instead, use
the use-devel-checklib script.

=head1 HOW IT WORKS

You pass named parameters to a function, describing to it how to build
and link to the libraries.

It works by trying to compile this:

    int main(void) { return 0; }

and linking it to the specified libraries.  If something pops out the end
which looks executable, then we know that it worked.  That tiny program is
built once for each library that you specify, and (without linking) once
for each header file.

=head1 FUNCTIONS

All of these take the same named parameters and are exported by default.
To avoid exporting them, C<use Devel::CheckLib ()>.

=head2 assert_lib

This takes several named parameters, all of which are optional, and dies
with an error message if any of the libraries listed can
not be found.  B<Note>: dying in a Makefile.PL or Build.PL may provoke
a 'FAIL' report from CPAN Testers' automated smoke testers.  Use 
C<check_lib_or_exit> instead.

The named parameters are:

=over

=item lib

Must be either a string with the name of a single 
library or a reference to an array of strings of library names.  Depending
on the compiler found, library names will be fed to the compiler either as
C<-l> arguments or as C<.lib> file names.  (E.g. C<-ljpeg> or C<jpeg.lib>)

=item libpath

a string or an array of strings
representing additional paths to search for libraries.

=item LIBS

a C<ExtUtils::MakeMaker>-style space-seperated list of
libraries (each preceded by '-l') and directories (preceded by '-L').

This can also be supplied on the command-line.

=back

And libraries are no use without header files, so ...

=over

=item header

Must be either a string with the name of a single 
header file or a reference to an array of strings of header file names.

=item incpath

a string or an array of strings
representing additional paths to search for headers.

=item INC

a C<ExtUtils::MakeMaker>-style space-seperated list of
incpaths, each preceded by '-I'.

This can also be supplied on the command-line.

=back

=head2 check_lib_or_exit

This behaves exactly the same as C<assert_lib()> except that instead of
dieing, it warns (with exactly the same error message) and exits.
This is intended for use in Makefile.PL / Build.PL
when you might want to prompt the user for various paths and
things before checking that what they've told you is sane.

If any library or header is missing, it exits with an exit value of 0 to avoid
causing a CPAN Testers 'FAIL' report.  CPAN Testers should ignore this
result -- which is what you want if an external library dependency is not
available.

=cut

sub check_lib_or_exit {
    eval 'assert_lib(@_)';
    if($@) {
        warn $@;
        exit;
    }
}

sub assert_lib {
    my %args = @_;
    my (@libs, @libpaths, @headers, @incpaths);

    # FIXME: these four just SCREAM "refactor" at me
    @libs = (ref($args{lib}) ? @{$args{lib}} : $args{lib}) 
        if $args{lib};
    @libpaths = (ref($args{libpath}) ? @{$args{libpath}} : $args{libpath}) 
        if $args{libpath};
    @headers = (ref($args{header}) ? @{$args{header}} : $args{header}) 
        if $args{header};
    @incpaths = (ref($args{incpath}) ? @{$args{incpath}} : $args{incpath}) 
        if $args{incpath};

    # work-a-like for Makefile.PL's LIBS and INC arguments
    # if given as command-line argument, append to %args
    for my $arg (@ARGV) {
        for my $mm_attr_key qw(LIBS INC) {
            if (my ($mm_attr_value) = $arg =~ /\A $mm_attr_key = (.*)/x) {
            # it is tempting to put some \s* into the expression, but the
            # MM command-line parser only accepts LIBS etc. followed by =,
            # so we should not be any more lenient with whitespace than that
                $args{$mm_attr_key} .= " $mm_attr_value";
            }
        }
    }

    # using special form of split to trim whitespace
    if(defined($args{LIBS})) {
        foreach my $arg (split(' ', $args{LIBS})) {
            die("LIBS argument badly-formed: $arg\n") unless($arg =~ /^-l/i);