Perl Sucks - and what to do about it

Perl Sucks! (and what to do about it)

What this talk is not • “Wah, no one uses ‘use strict’” • “People’s perception of Perl is wrong” • “The CPAN/mailing list/a other website isn’t exactly how I like it” • “The garbage collection de-allocation routine isn’t very efﬁcent”

What this talk is • What’s a few major annoyances with Perl • What we the humble programmer can do to work around them

scp ~/bin nethost:

ssh newhost

jabme -m ‘compile done’

Module “Jabber::Lite” not found

-bash: jabme: /usr/local/bin/ perl: bad interpreter: No such ﬁle or directory

My Scripts Need • A particular version of Perl • A set of Perl modules

#!/usr/bin/perl use strict; use warnings; use XML::LibXML; use Template; use DBD::SQLite; use CGI; use Parse::RecDescent; use List::MoreUtils; use Moose; print quot;Hello Worldnquot;;

Make an executable • perl -MCPAN -e ‘install PAR::Packer’ • pp -o hellow hellow.pl • ...copy “hellow” to new computer • ./hellow Hello World

#!/usr/bin/perl use strict; use warnings; print quot;Hello Worldnquot;;

Build our own Perl and ship the whole thing

Get Stable Perl • lwp-request $CPAN_URL > perl-5.8.8.tar.gz • gunzip -c perl-5.8.8.tar.gz | tar -xvf - • cd perl-5.8.8

Tell it where to go • mkdir -p /User/mark/bin/perl5.8.8 • ./conﬁgure.gnu --preﬁx=/User/mark/bin/ perl5.8.8

Install it • make • make test • make install

We now have our own perl in ~/bin

We can install it’s own modules

~/bin/perl5.8.8/bin/perl -MCPAN -e ‘install Template’

Problem: different paths • /home/mark/bin/myperl • /home/mfowler/bin/myperl • /home/nisuser/bin/myperl

mv ~/bin/perl5.8.8 whatever

whatever/bin/perl -e ‘use Storable’

Can't locate Storable.pm in @INC (@INC contains: /User/mark/bin/perl5.8.8/lib/5.8.8/ darwin-2level /User/mark/bin/perl5.8.8/lib/ 5.8.8 /User/mark/bin/perl5.8.8/lib/site_perl/ 5.8.8/darwin-2level /User/mark/bin/perl5.8.8/lib/ site_perl/5.8.8 /User/mark/bin/perl5.8.8/lib/ site_perl .) at -e line 1.

Can't locate Storable.pm in @INC (@INC contains: ../lib/5.8.8/darwin-2level ../lib/5.8.8 ../lib/site_perl/5.8.8/darwin-2level ../lib/site_perl/5.8.8 ../lib/site_perl .) at -e line 1.

bleed to the rescue

B E TA Get Bleed Perl • lwp-request $CPAN_URL > perl-5.9.5.tar.gz • gunzip -c perl-5.9.5.tar.gz | tar -xvf - • cd perl-5.9.5

B E TA Tell it where to go • mkdir -p /User/mark/bin/perl5.9.5 • ./Conﬁgure -Dusedevel -Dpreﬁx=/User/ mark/bin/perl5.9.5 -Duserelocatableinc -d

B E TA Install it • make • make test • make install

B E TA mv ~/bin/perl5.9.5 whatever

B E TA whatever/bin/perl5.9.5 -e ‘use Storable’

Exception Handling

Java try { throw new NoCheeseException(“redo”); } catch (NoCheeseException e) { system.err.println(e.toString()); }

Perl eval { die new NoCheeseError->new(“redo”); }; if (blessed($@) && $@->isa(“NoCheeseException”)) { print STDERR $@; } elsif ($@) { die $@ }

Perl has SUCKY SYNTAX

Sins include:

die “stop my program”;

die “some catchable exception”;

eval “some code to be compiled”;

eval { # run some code to catch errors in };

We can ﬁx it!

(still) Perl try { throw NoCheeseException “redo”; } catch NoCheeseException with { print STDERR $@; };

try { throw NoCheeseException “redo”; } catch NoCheeseException with { print STDERR $@; } catch AnotherError with { print STDERR “oopsn”; };

try( sub { throw NoCheeseException “redo”; }, catch NoCheeseException with(sub { print STDERR $@; }, catch AnotherError with(sub { print STDERR “oopsn”; })));

try( sub { NoCheeseException->throw( “redo” ); }, NoCheeseException->catch( with(sub { print STDERR $@; }, AnotherError->catch( with(sub { print STDERR “oopsn”; })))));

sub with (&;@) { return @_ }

try( sub { NoCheeseException->throw( “redo” ); }, NoCheeseException->catch( with(sub { print STDERR $@; }, AnotherError->catch( with(sub { print STDERR “oopsn”; })))));

try( sub { NoCheeseException->throw( “redo” ); }, NoCheeseException->catch( sub { print STDERR $@; }, AnotherError->catch( sub { print STDERR “oopsn”; })));

package OurErrorSuperclass; sub catch { my $class = shift; my $action = shift; return +{ class => $class, action => $action }, @_; }

try( sub { NoCheeseException->throw( “redo” ); }, NoCheeseException->catch( sub { print STDERR $@; }, AnotherError->catch( sub { print STDERR “oopsn”; })));

try( sub { NoCheeseException->throw( “redo” ); }, NoCheeseException->catch( sub { print STDERR $@; }, +{ class => “AnotherError”, action => sub { print STDERR “oopsn” } }));

try( sub { NoCheeseException->throw( “redo” ); }, +{ class => “NoCheeseException”, action => sub { print STDERR $@; } }, +{ class => “AnotherError”, action => sub { print STDERR “oopsn” } });

(still) Perl try { throw NoCheeseException “redo”; } catch NoCheeseException with { print STDERR $@; };

sub foo { try { return “This doesn’t return from foo”; } catch NoCheeseException with { print STDERR $@; }; }

sub foo { eval { return “This doesn’t return from foo”; }; if ($@) { .... } }

sub foo { try { return “This doesn’t return from foo”; } catch NoCheeseException with { print STDERR $@; }; }

sub foo { try { rreturn “This doesn’t return from foo”; } catch NoCheeseException with { print STDERR $@; } and return allowed; }

MyException NoDairyException NoSpreadException NoMilkException NoButterException NoMargException NoCheeseException NoEdamException NoStiltonException NoBrieException

package NoDairyException; our @ISA = qw(MyError); package NoMilkException; our @ISA = qw(NoDairyException); package NoSpreadException; our @ISA = qw(NoDairyException); package NoButterException; our @ISA = qw(NoSpreadException); package NoMargException; our @ISA = qw(NoMargeException); package NoCheeseException; our @ISA = qw(NoDairyException); package NoEdamException; our @ISA = qw(NoCheeseException); package NoStiltonException; our @ISA = qw(NoCheeseException); package NoBrieException; our@ISA = qw(NoCheeseException);

Exceptions::deﬁne { exception NoDairyException; exception NoSpreadException extends NoDairyException; exception NoButterException extends NoSpreadException; exception NoMargException extends NoSpreadException; exception NoMilkException extends NoDairyException; exception NoCheeseException extends NoDairyException; exception NoEdamException extends NoCheeseException; exception NoStiltonException extends NoCheeseException; exception NoBrieException extends NoCheeseException; };

But it’s a scripting language!

Don’t you just love the Template Toolkit?

bash$ tpage [% FOR a = [1..5]; a; END %] ^D 12345 bash$

#!perl $whereami = “Vienna”; print “Hello $whereami!n”;

#!tpage [% whereami = “Vienna” -%] Hello [% whereami %]!

bash$ ./hellov.tp

bash$ ./hellov.tp -bash: ./hellov.tp: tpage: bad interpreter: No such ﬁle or directory

where bash ﬁnds the Executable code to #!tpage load into memory [% whereami = “Vienna” -%] Hello [% whereami %]!

bash$ cat tpage #!/usr/bin/perl -w use strict; use Template; use AppConﬁg; …

Two possible solutions

Method one: Abuse source ﬁlters

• “Source ﬁlters are a way to change your source code before perl gets to see it”

#!/usr/bin/perl use strict; use warnings; use EnableDebugging; # DEBUG printing stuff out print quot;hinquot;;

#!/usr/bin/perl use strict; use warnings; use EnableDebugging; ;print STDERR “DEBUG: printing stuff outn”; print quot;hinquot;;

package EnableDebugging; use Filter::Simple; FILTER { s{#s*DEBUGs+(.*)} {;print STDERR q<DEBUG: $1>, quot;nquot;;}; }; 1;

package tpage; use Filter::Simple; FILTER { s{#s*DEBUGs+(.*)} {;print STDERR q<DEBUG: $1>, quot;nquot;;}; }; 1;

package tpage; use Filter::Simple; FILTER { $template .= $_; $_ = “”; }; 1;

package tpage; use Filter::Simple; FILTER { $template .= $_; $_ = “”; }; END { use Template; Template->new->process($template); }

#!/usr/bin/perl use tpage; [%- whereami = “Vienna” -%] Hello [% whereami %]!

2. Build our own executable

#include <EXTERN.h> #include <perl.h> static PerlInterpreter *my_perl; int main(int argc, char **argv, char **env) { char *embedding[] = { quot;quot;, quot;-equot;, quot;0quot; }; PERL_SYS_INIT3(&argc,&argv,&env); my_perl = perl_alloc(); perl_construct(my_perl); perl_parse(my_perl, NULL, 3, embedding, NULL); PL_exit_ﬂags |= PERL_EXIT_DESTRUCT_END; perl_run(my_perl); eval_pv(quot;print qq'oh hain’;quot;, TRUE); perl_destruct(my_perl); perl_free(my_perl); PERL_SYS_TERM(); }

( stolen from “perldoc perlembed”)

#include <EXTERN.h> #include <perl.h> static PerlInterpreter *my_perl; int main(int argc, char **argv, char **env) { char *embedding[] = { quot;quot;, quot;-equot;, quot;0quot; }; PERL_SYS_INIT3(&argc,&argv,&env); my_perl = perl_alloc(); perl_construct(my_perl); perl_parse(my_perl, NULL, 3, embedding, NULL); PL_exit_ﬂags |= PERL_EXIT_DESTRUCT_END; perl_run(my_perl); eval_pv(quot;print qq'o hain';quot;, TRUE); perl_destruct(my_perl); perl_free(my_perl); PERL_SYS_TERM(); }

#include <EXTERN.h> #include <perl.h> static PerlInterpreter *my_perl; int main(int argc, char **argv, char **env) { char *embedding[] = { quot;quot;, quot;-equot;, quot;0quot; }; PERL_SYS_INIT3(&argc,&argv,&env); my_perl = perl_alloc(); perl_construct(my_perl); perl_parse(my_perl, NULL, 3, embedding, NULL); PL_exit_ﬂags |= PERL_EXIT_DESTRUCT_END; perl_run(my_perl); eval_pv(quot;print qq’o hain’;quot;, TRUE); perl_destruct(my_perl); perl_free(my_perl); PERL_SYS_TERM(); }

cc -o hellow hellow.c `perl -MExtUtils::Embed -e ccopts -e ldopts`

bash$ ./hellow o hai

#include <EXTERN.h> #include <perl.h> static PerlInterpreter *my_perl; int main(int argc, char **argv, char **env) { char *embedding[] = { quot;quot;, quot;-equot;, quot;0quot; }; PERL_SYS_INIT3(&argc,&argv,&env); my_perl = perl_alloc(); perl_construct(my_perl); perl_parse(my_perl, NULL, 3, embedding, NULL); PL_exit_ﬂags |= PERL_EXIT_DESTRUCT_END; perl_run(my_perl); eval_pv(quot;print qq'o hain';quot;, TRUE); perl_destruct(my_perl); perl_free(my_perl); PERL_SYS_TERM(); }

#include <EXTERN.h> #include <perl.h> static PerlInterpreter *my_perl; int main(int argc, char **argv, char **env) { char *embedding[] = { quot;quot;, quot;-equot;, quot;0quot; }; PERL_SYS_INIT3(&argc,&argv,&env); my_perl = perl_alloc(); perl_construct(my_perl); perl_parse(my_perl, NULL, 3, embedding, NULL); PL_exit_ﬂags |= PERL_EXIT_DESTRUCT_END; perl_run(my_perl); eval_pv(quot;print qq’o hain’;quot;, TRUE); perl_destruct(my_perl); perl_free(my_perl); PERL_SYS_TERM(); }

#include <EXTERN.h> #include <perl.h> static PerlInterpreter *my_perl; int main(int argc, char **argv, char **env) { char *embedding[] = { quot;quot;, quot;-equot;, quot;0quot;, argv[0]}; PERL_SYS_INIT3(&argc,&argv,&env); my_perl = perl_alloc(); perl_construct(my_perl); perl_parse(my_perl, NULL, 4, embedding, NULL); PL_exit_ﬂags |= PERL_EXIT_DESTRUCT_END; perl_run(my_perl); eval_pv(quot;print qq’o hain’;quot;, TRUE); perl_destruct(my_perl); perl_free(my_perl); PERL_SYS_TERM(); }

#include <EXTERN.h> #include <perl.h> static PerlInterpreter *my_perl; int main(int argc, char **argv, char **env) { char *embedding[] = { quot;quot;, quot;-equot;, quot;0quot;, argv[0]}; PERL_SYS_INIT3(&argc,&argv,&env); my_perl = perl_alloc(); perl_construct(my_perl); perl_parse(my_perl, NULL, 4, embedding, NULL); PL_exit_ﬂags |= PERL_EXIT_DESTRUCT_END; perl_run(my_perl); eval_pv( “use Template Template->new->process($ARGV[0])quot;, TRUE); perl_destruct(my_perl); perl_free(my_perl); PERL_SYS_TERM(); }

cc -o mytt mytt.c `perl -MExtUtils::Embed -e ccopts -e ldopts`

now Executable code to load into memory #!mytt [% whereami = “Vienna” -%] Hello [% whereami %]!

#include <EXTERN.h> #include <perl.h> static PerlInterpreter *my_perl; “hellov.tp” int main(int argc, char **argv, char **env) { char *embedding[] = { quot;quot;, quot;-equot;, quot;0quot;, argv[0]}; PERL_SYS_INIT3(&argc,&argv,&env); my_perl = perl_alloc(); perl_construct(my_perl); perl_parse(my_perl, NULL, 4, embedding, NULL); PL_exit_ﬂags |= PERL_EXIT_DESTRUCT_END; perl_run(my_perl); eval_pv( “use Template Template->new->process($ARGV[0])quot;, TRUE); perl_destruct(my_perl); perl_free(my_perl); PERL_SYS_TERM(); }

A LP H A We’ve already seen source ﬁlters

B E TA PPI • Pure Perl parser • Only parses a subset of Perl • Can’t tell the difference between certain Perl constructs • This said - very very good at what it does

A LP H A MAD

A LP H A ./conﬁgure.gnu --preﬁx=~/bin/perl595 -Dusedevel -Dmad=y make && make test && make install

A LP H A my $a = 1; my $b = 2; print $a + $b;

A LP H A PERL_XMLDUMP=quot;foo.xmlquot; ./perl foo.pl

</op_nextstate> A LP <op_sassign seq=quot;9 -> 10quot; H flags=quot;VOID,KIDS,STACKEDquot;> A <op_leave seq=quot;0 -> DONEquot; targ=quot;1quot; flags=quot;VOID,KIDS,PARENSquot; private=quot;REFCOUNTEDquot; refcnt=quot;1quot;> <op_enter seq=quot;1 -> 2quot; /> <op_null seq=quot;0 -> (2)quot; flags=quot;VOIDquot;> <madprops> <mad_sv key=quot;;quot; val=quot;quot;/> </madprops> <madprops> </op_null> <op_nextstate seq=quot;2 -> 3quot; flags=quot;VOIDquot; line=quot;1quot; package=quot;mainquot;> <madprops> <mad_sv key=quot;;quot; val=quot;;quot;/> <mad_sv key=quot;#;quot; val=quot;
quot;/> </madprops> <mad_sv key=quot;oquot; val=quot;=quot;/> </op_nextstate> <op_sassign seq=quot;5 -> 6quot; flags=quot;VOID,KIDS,STACKEDquot;> <madprops> <mad_sv key=quot;oquot; val=quot;=quot;/> <mad_sv key=quot;_oquot; val=quot; quot;/> </madprops> <op_const seq=quot;3 -> 4quot; flags=quot;SCALARquot; IV=quot;1quot;> <mad_sv key=quot;_oquot; val=quot; quot;/> <madprops> <mad_sv key=quot;Xquot; val=quot;1quot;/> <mad_sv key=quot;_Xquot; val=quot; quot;/> </madprops> </op_const> <op_padsv seq=quot;4 -> 5quot; targ=quot;1quot; flags=quot;SCALAR,REF,MOD,SPECIALquot; private=quot;INTROquot;> <madprops> </madprops> <mad_sv key=quot;$quot; val=quot;$aquot;/> <mad_sv key=quot;_$quot; val=quot; quot;/> <mad_sv key=quot;dquot; val=quot;myquot;/> <mad_sv key=quot;_dquot; val=quot;quot;/> </madprops> </op_padsv> </op_sassign> <op_nextstate seq=quot;6 -> 7quot; flags=quot;VOIDquot; <op_const seq=quot;7 -> 8quot; flags=quot;SCALARquot; line=quot;2quot; package=quot;mainquot;> <madprops> <mad_sv key=quot;;quot; val=quot;;quot;/> <mad_sv key=quot;#;quot; val=quot;
quot;/> </madprops> </op_nextstate> <op_sassign seq=quot;9 -> 10quot; flags=quot;VOID,KIDS,STACKEDquot;> <madprops> IV=quot;2quot;> <mad_sv key=quot;oquot; val=quot;=quot;/> <mad_sv key=quot;_oquot; val=quot; quot;/> </madprops> <op_const seq=quot;7 -> 8quot; flags=quot;SCALARquot; IV=quot;2quot;> <madprops> <mad_sv key=quot;Xquot; val=quot;2quot;/> <mad_sv key=quot;_Xquot; val=quot; quot;/> <madprops> </madprops> </op_const> <op_padsv seq=quot;8 -> 9quot; targ=quot;2quot; flags=quot;SCALAR,REF,MOD,SPECIALquot; private=quot;INTROquot;> <madprops> <mad_sv key=quot;$quot; val=quot;$bquot;/> <mad_sv key=quot;_$quot; val=quot; quot;/> <mad_sv key=quot;dquot; val=quot;myquot;/> <mad_sv key=quot;Xquot; val=quot;2quot;/> </madprops> </op_padsv> </op_sassign> <op_nextstate seq=quot;10 -> 11quot; flags=quot;VOIDquot; line=quot;3quot; package=quot;mainquot;> <madprops> <mad_sv key=quot;;quot; val=quot;;quot;/> <mad_sv key=quot;_Xquot; val=quot; quot;/> <mad_sv key=quot;_;quot; val=quot;quot;/> <mad_sv key=quot;#;quot; val=quot;
quot;/> </madprops> </op_nextstate> <op_print seq=quot;15 -> 16quot; flags=quot;SCALAR,KIDSquot;> <madprops> <mad_sv key=quot;oquot; val=quot;printquot;/> </madprops> </madprops> <op_pushmark seq=quot;11 -> 12quot; flags=quot;SCALARquot; /> <op_add seq=quot;14 -> 15quot; targ=quot;3quot; flags=quot;SCALAR,KIDSquot;> <madprops> <mad_sv key=quot;oquot; val=quot;+quot;/> <mad_sv key=quot;_oquot; val=quot; quot;/> </madprops> <op_padsv seq=quot;12 -> 13quot; targ=quot;1quot; flags=quot;SCALARquot;> <madprops> </op_const> <mad_sv key=quot;$quot; val=quot;$aquot;/> <mad_sv key=quot;_$quot; val=quot; quot;/> </madprops> </op_padsv> <op_padsv seq=quot;13 -> 14quot; targ=quot;2quot; flags=quot;SCALARquot;> <madprops> <mad_sv key=quot;$quot; val=quot;$bquot;/> <mad_sv key=quot;_$quot; val=quot; quot;/> </madprops> <op_padsv seq=quot;8 -> 9quot; targ=quot;2quot; </op_padsv> </op_add> </op_print> <op_null seq=quot;0 -> (16)quot; flags=quot;VOIDquot; /> </op_leave> flags=quot;SCALAR,REF,MOD,SPECIALquot;

B::Generate • Can be used to create OP codes (i.e. compiled Perl code) directly from Perl

use B::Generate; # Do nothing, slowly. CHECK { my $null = new B::OP(quot;nullquot;,0); my $enter = new B::OP(quot;enterquot;,0); my $cop = new B::COP(0, quot;hiyaquot;, 0); my $leave = new B::LISTOP(quot;leavequot;, 0, $enter, $null); $leave->children(3); $enter->sibling($cop); $enter->next($cop); $cop->sibling($null); $null->next($leave); $cop->next($leave); # Tell Perl where to ﬁnd our tree. B::main_root($leave); B::main_start($enter); }

optomize.pm • Can be used to manipulate the OP codes after they’ve loaded • Kinda like source ﬁlters for compiled bypecode

Use? • PPI is reliable, but limited in it’s ability • Easy to try to do too much with • Other techniques are very unstable / new • B::Generate • optomize • MAD

A LP H A package main; use typesafety; # 'summary', 'debug'; my FooBar $foo; # establish type-checked variables my FooBar $bar; # FooBar is the base class of references $bar will hold my BazQux $baz; $foo = new FooBar; # this is okay, because $foo holds FooBars $bar = $foo; # this is okay, because $bar also holds FooBars # $foo = 10; # this would throw an error - 10 is not a FooBar # $baz = $foo; # not allowed - FooBar isn't a BazQux $foo = $baz; # is allowed - BazQux is a FooBar because of inheritance $bar = $foo->foo($baz, 1); # this is okay, as FooBar::foo() returns FooBars also typesafety::check(); # perform type check static analysis

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Perl Sucks - and what to do about it

by 2shortplanks on Aug 30, 2007

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