Item12956: Unitialized variable crash after using back button to return to edit, and save.

Reproducable on trunk.foswiki.org

• Edit a topic
• Save
• Use browser back button to return to edit
• Change and save again
• Confirm the Strike One suspicious change warning
• Crash

 Use of uninitialized value $values[0] in join or string at /usr/home/trunk.foswiki.org/core/lib/Foswiki/Prefs/Request.pm line 59.
 at /usr/local/lib/perl5/5.16/CGI/Carp.pm line 379.
   CGI::Carp::realdie("Use of uninitialized value \$values[0] in join or string at /u"...) called at /usr/local/lib/perl5/5.16/CGI/Carp.pm line 468
   CGI::Carp::die("Use of uninitialized value \$values[0] in join or string at /u"...) called at /usr/home/trunk.foswiki.org/core/lib/AssertOn.pm line 14
   Assert::__ANON__("Use of uninitialized value \$values[0] in join or string at /u"...) called at /usr/home/trunk.foswiki.org/core/lib/Foswiki/Prefs/Request.pm line 59
   Foswiki::Prefs::Request::set(Foswiki::Request=HASH(0x802942e58), Foswiki::Meta=HASH(0x8042b9828)) called at /usr/home/trunk.foswiki.org/core/lib/Foswiki/UI/Save.pm line 222
   Foswiki::UI::Save::buildNewTopic(Foswiki=HASH(0x802c599a8), Foswiki::Meta=HASH(0x8042b9828), "save") called at /usr/home/trunk.foswiki.org/core/lib/Foswiki/UI/Save.pm line 635
   Foswiki::UI::Save::save(Foswiki=HASH(0x802c599a8)) called at /usr/home/trunk.foswiki.org/core/lib/Foswiki/UI.pm line 346
   Foswiki::UI::__ANON__() called at /usr/local/lib/perl5/site_perl/5.16/Error.pm line 421
   eval {...} called at /usr/local/lib/perl5/site_perl/5.16/Error.pm line 413
   Error::subs::try(CODE(0x8010915d0), HASH(0x802c59468)) called at /usr/home/trunk.foswiki.org/core/lib/Foswiki/UI.pm line 467
   Foswiki::UI::_execute(Foswiki::Request=HASH(0x802942e58), CODE(0x8029a3750), "save", 1) called at /usr/home/trunk.foswiki.org/core/lib/Foswiki/UI.pm line 299
   Foswiki::UI::handleRequest(Foswiki::Request=HASH(0x802942e58)) called at /usr/home/trunk.foswiki.org/core/lib/Foswiki/Engine/CGI.pm line 89
   Foswiki::Engine::CGI::run(Foswiki::Engine::CGI=HASH(0x8018c2540)) called at /home/trunk.foswiki.org/core/bin/save line 29.

-- GeorgeClark - 02 Jul 2014

I think this needs an assist from you as well Crawford. The difference is that on a save, the empty params are set to '', and after the redirect they are undef. Below is a snippet of a Data::Dumper dump of the Foswiki::Request:

Save

                   'param' => {
                                'redirectto' => [
                                                  ''
                                                ],
                                'action_addform' => [
                                                      ''
                                                    ],
                                'action_save' => [
                                                   'Save'
                                                 ],
                                'Default+ALLOWTOPICVIEW' => [
                                                              'undefined'
                                                            ],
                                'nowysiwyg' => [
                                                 ''
                                               ],
                                'Set+ALLOWTOPICCHANGE' => [
                                                            'undefined'
                                                          ],
                                'action_checkpoint' => [
                                                         ''
                                                       ],
                                'Local+PERMSET_CHANGE' => [
                                                            'default'
                                                          ],
                                'Default+PERMSET_CHANGE' => [
                                                              'default'
                                                            ],
                                'Local+PERMSET_VIEW' => [
                                                          'everybody'
                                                        ],

Redirect

                   'param' => {
                                'redirectto' => [
                                                  undef
                                                ],
                                'action_addform' => [
                                                      undef
                                                    ],
                                'action_save' => [
                                                   'Save'
                                                 ],
                                'Default+ALLOWTOPICVIEW' => [
                                                              'undefined'
                                                            ],
                                'nowysiwyg' => [
                                                 undef
                                               ],
                                'Set+ALLOWTOPICCHANGE' => [
                                                            'undefined'
                                                          ],
                                'action_checkpoint' => [
                                                         undef
                                                       ],
                                'Local+PERMSET_CHANGE' => [
                                                            'default'
                                                          ],
                                'Default+PERMSET_CHANGE' => [
                                                              'default'
                                                            ],
                                'Local+PERMSET_VIEW' => [
                                                          'everybody'
                                                        ],
                                'Default+DENYTOPICCHANGE' => [
                                                               'undefined'
                                                             ],

The fix is pretty simple if I can just check for defined in Foswiki::Prefs::Request::set, but is this where the problem lies, or is the triggered when the redirect cache rebuilds the query?

-- GeorgeClark - 02 Jul 2014

This seems to be a fix.

diff --git a/core/lib/Foswiki/Request.pm b/core/lib/Foswiki/Request.pm
index 62bb2c3..a8e8210 100644
--- a/core/lib/Foswiki/Request.pm
+++ b/core/lib/Foswiki/Request.pm
@@ -625,6 +625,7 @@ sub load {
         last if /^=$/;
         my ( $key, $value ) =
           map { defined $_ ? Foswiki::urlDecode($_) : $_ } split /=/;
+        $value = '' unless defined $value;
         if ( exists $param{$key} ) {
             push @{ $param{$key} }, $value;
         }

-- GeorgeClark - 02 Jul 2014

Whoops - broke the unit tests. Reopening.

-- GeorgeClark - 05 Jul 2014

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