awesome programmers.... im trying to studying perl opengl... i install all the modules and it went ok.. everythings fine! except for this...
my first code is
use OpenGL;
use SDL;
glpOpenWindow();
print "Return to exit\n";
while(<>){
exit;
}
and the result is
Goto undefined subroutine &AutoLoader::AUTOLOAD at C:/strawberry/perl/site/lib/OpenGL.pm line 6110.
i tried the test.pl of OpenGL.. awesomely works fine but this line of me is weird!
Below is the source code of method AUTOLOAD from OpenGL.pm
sub AUTOLOAD {
# This AUTOLOAD is used to 'autoload' constants from the constant()
# XS function. If a constant is not found then control is passed
# to the AUTOLOAD in AutoLoader.
# NOTE: THIS AUTOLOAD FUNCTION IS FLAWED (but is the best we can do for now).
# Avoid old-style ``&CONST'' usage. Either remove the ``&'' or add ``()''.
if (#_ > 0) {
# Is it an old OpenGL-0.4 function? If so, remap it to newer variant
local($constname);
($constname = $AUTOLOAD) =~ s/.*:://;
if (grep ($_ eq $constname, #rename_old)) {
eval "sub $AUTOLOAD { $AUTOLOAD" . "_s(\#_) }";
goto &$AUTOLOAD;
}
$AutoLoader::AUTOLOAD = $AUTOLOAD;
goto &AutoLoader::AUTOLOAD; #LINE 6110
}
They have put in comment that THIS AUTOLOAD FUNCTION IS FLAWED so maybe the warning you are getting is not due to your program but the problem with module itself.
Related
i am switching my application from Perl 5.8.8 to Perl 5.16.3 and now i get tons of warnings about the following third party code in SOAP::Lite
unless (defined %{"$protocol_class\::Client::" )
The code produces the following warings:
Warning in Perl code: \t(Maybe you should just omit the defined()?)
Warning in Perl code: defined(%hash) is deprecated at /.../SOAP/Lite.pm
line ...
If i reduce it to a simple example it looks like
unless( defined %{"some::string"} )
Question: Why should someone interpret a string "some::string" as a hash %{"some::string"} and check if the hash is defined? It doen't make any sense to me. I want to replace this codepiece with something else without breaking the third party module so i can focus on real important warnings and errors.
Here is the whole function. I don't know if this helps because think its some kind of Guru code which is a little bit hard to understand
sub proxy {
my $self = shift;
$self = $self->new() if not ref $self;
my $class = ref $self;
return $self->{_proxy} unless #_;
$_[0] =~ /^(\w+):/ or die "proxy: transport protocol not specified\n";
my $protocol = uc "$1"; # untainted now
# HTTPS is handled by HTTP class
$protocol =~s/^HTTPS$/HTTP/;
(my $protocol_class = "${class}::$protocol") =~ s/-/_/g;
no strict 'refs';
unless (defined %{"$protocol_class\::Client::"}
&& UNIVERSAL::can("$protocol_class\::Client" => 'new')
) {
eval "require $protocol_class";
die "Unsupported protocol '$protocol'\n"
if $# =~ m!^Can\'t locate SOAP/Transport/!;
die if $#;
}
$protocol_class .= "::Client";
return $self->{_proxy} = $protocol_class->new(endpoint => shift, #_);
}
The construct %Package:: gives access to a package's stash, i.e. the symbol table hash.
All this code is doing is checking whether a given package has been loaded (in which case its stash will exist) and that there is a new method for the package. If not then require is used to load the module.
The call to UNIVERSAL::can('package', 'method') is normally written as 'package'->can('method') and you can change that here if you like, but the code will work as it stands.
I suggest you do just as the warnings say, and omit the defined. It would also be nicer if you put the package name in its own variable instead of using the interpolated double-quoted string twice, and you can use the conventional call to can as I have described. It would look like this
my $package = "${protocol_class}::Client";
unless ( %{"${package}::"} and $package->can('new') ) {
# load missing module
}
EDIT:
I will try a better explication this time, this is the exact code from my script (sorry for all them coments, they are a result of your sugestions, and apear in the video below).
#use warnings;
#use Data::Dumper;
open(my $tmp_file, ">>", "/tmp/some_bad.log") or die "Can not open log file: $!\n";
#if( $id_client != "")
#allowed_locations = ();
#print $tmp_file "Before the if: ". Data::Dumper->Dump([\#allowed_locations, $id_client]) . "";
if( $id_client )
{
# print $tmp_file "Start the if: ". Data::Dumper->Dump([\#allowed_locations, $id_client]) . "";
# my $q = "select distinct id_location from locations inner join address using (id_db5_address) inner join zona_rural_detaliat using (id_city) where id_client=$id_client";
# my $st = &sql_special_transaction($sql_local_host, $sql_local_database, $sql_local_root, $sql_local_root_password, $q);
# print $tmp_file "Before the while loop: ref(st)='". ref($st) . "\n";
# while((my $id)=$st->fetchrow())
# {
# print $tmp_file "Row the while loop: ". Data::Dumper->Dump([$id]) . "";
# my $id = 12121212;
# push(#allowed_locations, $id);
# }
# print $tmp_file "After the while loop: ref(st)='". ref($st) . "\n";
# my($a) = 1;
#} else {
# my($a) = 0;
}
#print $tmp_file "After the if: ". Data::Dumper->Dump([\#allowed_locations, $id_client]) . "";
close($tmp_file) or die "Can not close file: $!\n";
#&html_error(#allowed_locations);
First off all, somebody said that I should try to run it in command line, the script works fine in command line (no warnings, It was uncommented then), but when triyng to load in via apache in the browser it fails, please see this video where I captured the script behavior, what I tried to show in the video:
I have opened 2 tabs the first doesn't define the variable $id_client, the second defines the variable $id_client that is read from GET: ?id_client=36124 => $id_client = 36124; , both of them include the library in the video "locallib.pl"
When running the script with all the
new code commented the page loads
when uncoment the line that defines
the #allowed_locations = (); the
script fails
leave this definition and uncoment
the if block, and the definition of
my $a; in the if block; Now the script works fine when $id_client is
defined, but fails when $id_client
is not defined
Uncoment the else block and the
definition of my $a; in the else
block. Now the script works fine
with or without $id_client
now comment all the my $a;
definisions and comment the else
block, the script fails
but if I'm using open() to open
a file before the IF, and
close() to close it after the if it does't fail even if the IF block
is empty and event if there is no
else block
I have replicated all the steps when running the script in the command line, and the script worked after each step.
I know it sounds like something that cannot be the behavior of the script, but please watch the video (2 minutes), maybe you will notice something that I'm doing wrong there.
Using perl version:
[root#db]# perl -v
This is perl, v5.8.6 built for i386-linux-thread-mult
Somebody asked if I don't have a test server, answer: NO, my company has a production server that has multiple purposes, not only the web interface, and I cannot risk to update the kernel or the perl version, and cannot risk instaling any debuger, as the company owners say: "If it works, leave it alone", and for them the solution with my ($a); is perfect beacause it works, I'm asking here just for me, to learn more about perl, and to understand what is going wrong and what can I do better next time.
Thank you.
P.S. hope this new approach will restore some of my -1 :)
EDIT:
I had success starting the error logging, and found this in the error log after each step that resulted in a failure I got this messages:
[Thu Jul 15 14:29:19 2010] [error] locallib.pl did not return a true value at /var/www/html/rdsdb4/cgi-bin/clients/quicksearch.cgi line 2.
[Thu Jul 15 14:29:19 2010] [error] Premature end of script headers: quicksearch.cgi
What I found is that this code is at the end of the main code in the locallib.pl after this there are sub definitions, and locallib.pl is a library not a program file, so it's last statement must returns true. , a simple 1; statement at the end of the library ensures that (I put it after sub definitions to ensure that noobody writes code in the main after the 1;) and the problem was fixed.
Don't know why in CLI it had no problem ...
Maybe I will get a lot of down votes now ( be gentle :) ) , but what can I do ...and I hope that some newbies will read this and learn something from my mistake.
Thank you all for your help.
You need to explicitly check for definedness.
If you want to enter the loop when $client is defined,
use if ( defined $client ).
If you want to enter the loop when $client is defined and a valid integer,
use if ( defined $client && $client =~ /^-?\d+$/ ).
I assume it's an integer from the context, if it can be a float, the regex needs to be enhanced - there's a standard Perl library containing pre-canned regexes, including ones to match floats. If you require a non-negative int, drop -? from regex's start.
If you want to enter the loop when $client is defined and a non-zero (and assuming it shouldn't ever be an empty string),
use if ( $client ).
If you want to enter the loop when $client is defined and a valid non-zero int,
use if ( $client && $client =~ /^-?\d+$/ ).
Your #ids is "undef" when if condition is false, which may break the code later on if it relies on #ids being an array. Since you didn't actually specify how the script breaks without an else, this is the most likely cause.
Please see if this version works (use whichever "if" condition from above you need, I picked the last one as it appears to match the closest witrh the original code's intent - only enter for non-zero integers):
UPDATED CODE WITH DEBUGGING
use Data::Dumper;
open(my $tmp_file, ">", "/tmp/some_bad.log") or die "Can not open log file: $!\n";
#ids = (); # Do this first so #ids is always an array, even for non-client!
print $tmp_file "Before the if: ". Data::Dumper->Dump([\#ids, $client]) . "\n";
if ( $client && $client =~ /^-?\d+$/ ) # First expression catches undef and zero
{
print $tmp_file "Start the if: ". Data::Dumper->Dump([\#ids, $client]) . "\n";
my $st = &sql_query("select id from table where client=$client");
print $tmp_file "Before the while loop: ref(st)='". ref($st) . "'\n";
while(my $row = $st->fetchrow())
{
print $tmp_file "Row the while loop: ". Data::Dumper->Dump([row]) . "'\n";
push(#ids, $row->[0]);
}
print $tmp_file "After the while loop: ref(st)='". ref($st) . "'\n";
# No need to undef since both variables are lexically in this block only
}
print $tmp_file "After the if\n";
close($tmp_file) or die "Can not close file: $!\n";
when checking against a string, == and != should be respectively 'eq' or 'ne'
if( $client != "" )
should be
if( $client ne "" )
Otherwise you don't get what you're expecting to get.
Always begin your script with :
use warnings;
use strict;
these will give you usefull informations.
Then you could write :
my #ids;
if (defined $client) {
#ids = (); # not necessary if you run this part only once
my $st = sql_query("select id from table where client=$client");
while( my ($id) = $st->fetchrow ) {
push #ids, $id;
}
} else {
warn '$client not defined';
}
if (#ids) { # Your query returned something
# do stuff with #ids
} else {
warn "client '$client' does not exist in database";
}
Note: this answer was deleted because I consider that this is not a real question. I am undeleting it to save other people repeating this.
Instead of
if( $client != "" )
try
if ($client)
Also, Perl debugging is easier if you
use warnings;
use strict;
What I found is that this code is at the end of the main code in the locallib.pl after this there are sub definitions, and locallib.pl is a library not a program file, so it's last statement must returns true, a simple 1; statement at the end of the library ensures that (put it after sub definitions to ensure that noobody writes code in the main after the 1;) and the problem was fixed.
The conclusion:
I have learned that every time you write a library or modify one, ensure that it's last statment returns true;
Oh my... Try this as an example instead...
# Move the logic into a subroutine
# Forward definition so perl knows func exists
sub getClientIds($);
# Call subroutine to find id's - defined later.
my #ids_from_database = &getClientIds("Joe Smith");
# If sub returned an empty list () then variable will be false.
# Otherwise, print each ID we found.
if (#ids_from_database) {
foreach my $i (#ids_from_database) {
print "Found ID $i \n";
}
} else {
print "Found nothing! \n";
}
# This is the end of the "main" code - now we define the logic.
# Here's the real work
sub getClientIds($) {
my $client = shift #_; # assign first parameter to var $client
my #ids = (); # what we will return
# ensure we weren't called with &getClientIds("") or something...
if (not $client) {
print "I really need you to give me a parameter...\n";
return #ids;
}
# I'm assuming the query is string based, so probably need to put it
# inside \"quotes\"
my $st = &sql_query("select id from table where client=\"$client\"");
# Did sql_query() fail?
if (not $st) {
print "Oops someone made a problem in the SQL...\n";
return #ids;
}
my #result;
# Returns a list, so putting it in a list and then pulling the first element
# in two steps instead of one.
while (#result = $st->fetchrow()) {
push #ids, $result[0];
}
# Always a good idea to clean up once you're done.
$st->finish();
return #ids;
}
To your specific questions:
If you want to test if $client is defined, you want "if ( eval { defined $client; } )", but that's almost certainly NOT what you're looking for! It's far easier to ensure $client has some definition early in the program (e.g. $client = "";). Also note Kaklon's answer about the difference between ne and !=
if (X) { stuff } else { } is not valid perl. You could do: if (X) { stuff } else { 1; } but that's kind of begging the question, because the real issue is the test of the variable, not an else clause.
Sorry, no clue on that - I think the problem's elsewhere.
I also echo Kinopiko in recommending you add "use strict;" at the start of your program. That means that any $variable #that %you use has to be pre-defined as "my $varable; my #that; my %you;" It may seem like more work, but it's less work than trying to deal with undefined versus defined variables in code. It's a good habit to get into.
Note that my variables only live within the squiggliez in which they are defined (there's implicit squiggliez around the whole file:
my $x = 1;
if ($x == 1)
{
my $x = 2;
print "$x \n"; # prints 2. This is NOT the same $x as was set to 1 above.
}
print "$x \n"; # prints 1, because the $x in the squiggliez is gone.
I want something like..
all_objects.pl
my $sub = $ARGV[1];
...
#objs = get_all_objects();
for my $obj (#objs) {
// invoke subroutine $sub with param as $obj.
}
now if I say
all_objects.pl "print 'x '"
all_objects.pl "print '$_ '"
I should get
obj1 obj2 obj3 ...
i.e. the command line arg act as a subroutine in some way. Can this be achieved?
eval "" is bad. Use something like the following, if it fulfills your needs:
my ($sub) = #ARGV;
my %prepared = (
print => sub { print "$_[0]\n" },
woof => sub { $_[0]->woof },
meow => sub { $_[0]->meow },
);
#objs = get_all_objects();
for my $obj (#objs) {
$prepared{$sub}->($obj);
}
Update: For debugging purposes, Perl has a debugger: perldoc perldebug
Eval is evil unless you really know what you're doing (think of it as an unshielded thermonuclear nuke -- sure you could handle one if you had to, and it might even save the world, but you'd be better off leaving it as a last resort, and let the nuclear physicists deal with it.)
You could put your all_objects.pl code into a module, and then use the module on the command line:
put this into AllObjects.pm:
package AllObjects;
use strict;
use warnings;
sub get_all_objects
{
# code here...
}
1;
Now on the command line:
perl -I. -MAllObjects -wle'for my $obj (AllObjects::get_all_objects()) { print "object is $obj" }'
However, it's not really clear what you are trying to achieve with the overall design.
You can read more about perl command-line invokation at perldoc perlrun, and making modules at perldoc perlmod (as well as many posts here on Stack Overflow).
I'm working on a test framework in Perl. As part of the tests, I may need to add precondition or postcondition checks for any given test, but not necessarily for all of them. What I've got so far is something like:
eval "&verify_precondition_TEST$n";
print $# if $#;
Unfortunately, this outputs "Undefined subroutine &verify_precondition_TEST1 called at ..." if the function does not exist.
How can I determine ahead of time whether the function exists, before trying to call it?
Package::Name->can('function')
or
*Package::Name::function{CODE}
# or no strict; *{ "Package::Name::$function" }{CODE}
or just live with the exception. If you call the function in an eval and $# is set, then you can't call the function.
Finally, it sounds like you may want Test::Class instead of writing this yourself.
Edit: defined &function_name (or the no strict; defined &{ $function_name } variant), as mentioned in the other answers, looks to be the best way. UNIVERSAL::can is best for something you're going to call as a method (stylistically), and why bother messing around with the symbol table when Perl gives you syntax to do what you want.
Learning++ :)
sub function_exists {
no strict 'refs';
my $funcname = shift;
return \&{$funcname} if defined &{$funcname};
return;
}
if (my $subref = function_exists("verify_precondition_TEST$n") {
...
}
With defined:
if (eval "defined(&verify_precondition_TEST$n)") {
eval "&verify_precondition_TEST$n";
print $# if $#;
}
else {
print "verify_precondition_TEST$n does not exist\n";
}
EDIT: hmm, I only thought of eval as it was in the question but with symbolic references brought up with Leon Timmermans, couldn't you do
if (defined(&{"verify_precondition_TEST$n"}) {
&{"verify_precondition_TEST$n"};
print $# if $#;
}
else {
print "verify_precondition_TEST$n does not exist\n";
}
even with strict?
I had used Leon's approach, but when I had multiple packages, it failed. I'm not sure precisely why; I think it relates to the propagation of scope between namespaces. This is the solution I came up with.
my %symbols = ();
my $package = __PACKAGE__; # bring it in at run-time
{
no strict;
%symbols = %{$package . "::"}; #S ee Symbol Tables on perlmod
}
print "$funcname not defined\n" if (!defined($symbols{$funcname});
References:
__PACKAGE__ reference on the perlmod page.
Packages/__PACKAGE__reference on Perl Training Australia.
Requirement is to pass module name and function name from the command-line argument.
I need to get the command-line argument in the program and I need to call that function from that module
For example, calling a try.pl program with 2 arguments: MODULE1(Module name) Display(Function name)
perl try.pl MODULE1 Display
I want to some thing like this, but its not working, please guide me:
use $ARGV[0];
& $ARGV[0]::$ARGV[1]();
Assuming the function is not a class method, try this:
#!/usr/bin/perl
use strict;
use warnings;
my ( $package, $function ) = #ARGV;
eval "use $package (); ${package}::$function()";
die $# if $#;
Keep in mind that this technique is wide open to code injection. (The arguments could easily contain any Perl code instead of a module name.)
There's many ways to do this. One of them is:
#!/usr/bin/perl
use strict;
use warnings;
my ( $package, $function ) = #ARGV;
eval "use $package; 1" or die $#;
$package->$function();
Note the the first argument of the function will be $package.
Assuming the module exports the function, this should do:
perl -Mmodule -e function
If you want to make sure your perl script is secure (or at least, prevent yourself from accidentally doing something stupid), I'd avoid doing any kind of eval on data passed in to the script without at least some kind of checking. But, if you're doing some kind of checking anyway, and you end up explicitly checking the input, you might as well explicitly spell out witch methods you want to call. You could set up a hash with 'known good' methods, thus documenting everything that you want callable and protecting yourself at the same time.
my %routines = (
Module => {
Routine1 => \&Module::Method,
Routine2 => \&Module::Method2,
},
Module2 => {
# and so on
},
);
my $module = shift #ARGV;
my $routine = shift #ARGV;
if (defined $module
&& defined $routine
&& exists $routines{$module} # use `exists` to prevent
&& exists $routines{$module}{$routine}) # unnecessary autovivication
{
$routines{$module}{$routine}->(#ARGV); # with remaining command line args
}
else { } # error handling
As a neat side effect of this method, you can simply iterate through the methods available for any kind of help output:
print "Available commands:\n";
foreach my $module (keys %routines)
{
foreach my $routine (keys %$module)
{
print "$module::$routine\n";
}
}
As per Leon's, if the perl module doesn't export it, you can call it like so
perl -MMyModule -e 'MyModule::doit()'
provided that the sub is in that package.
If it exports the sub all the time (in #EXPORT), then Leon's will work:
perl -MMyModule -e doit
If it is an optional export (in #EXPORT_OK), then you can do it like this.
perl -MMyModule=doit -e doit
But the first will work in any case where the sub is defined to the package, and I'd probably use that one over the last one.
Always start your Perl like this:
use strict;
use warnings 'all';
Then do this:
no strict 'refs';
my ($class, $method) = #_;
(my $file = "$class.pm") =~ s/::/\//g;
require $file;
&{"$class\::$method"}();
Whatever you do, try not to eval "$string" ever.
Well, for your revised question, you can do this:
use strict;
use warnings;
{
no strict;
use Symbol qw<qualify>;
my $symb = qualify( $ARGV[1], $ARGV[0] );
unless ( defined &{$symb} ) {
die "&$ARGV[1] not defined to package $ARGV[0]\::";
}
&{$symb};
}
And because you're specifying it on the command line, the easiest way to include from the command line is the -M flag.
perl -MMyModule try.pl MyModule a_subroutine_which_does_something_cool
But you can always
eval "use $ARGV[0];";
But that's highly susceptible to injection:
perl try.pl "Carp; `do something disastrous`;" no_op
I'd use UNIVERSAL::require. It allows you to require or use a module from a variable. So your code would change to something like this:
use UNIVERSAL::require;
$ARGV[0]->use or die $UNIVERSAL::require::ERROR;
$ARGV[0]::$ARGV[1]();
Disclaimer: I did not test that code and I agree Robert P's comment about there probably being a better solution than passing these as command line arguments.