为什么我会得到“重新定义” 带有“使用常量”的警告 在 mod_perl 下？

Question

我使用 apache2 运行 CGI 脚本，并且在 error.log 中出现了以下警告行（我从输出中删除了所有类似的行）：

[Thu Jul 30 09:39:37 2009] upload.pl: Constant subroutine ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::UPLOAD_DIR redefined at /usr/share/perl/5.10/constant.pm line 115,  line 133.
Constant subroutine
    ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::BUFFER_SIZE redefined at /usr/share/perl/5.10/constant.pm line 115,  line 133 (#1)
[Thu Jul 30 09:39:37 2009] upload.pl: Constant subroutine ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::BUFFER_SIZE redefined at /usr/share/perl/5.10/constant.pm line 115,  line 133.
Constant subroutine
    ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::MAX_FILE_SIZE redefined at /usr/share/perl/5.10/constant.pm line 115,  line 133 (#1)
[Thu Jul 30 09:39:37 2009] upload.pl: Constant subroutine ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::MAX_FILE_SIZE redefined at /usr/share/perl/5.10/constant.pm line 115,  line 133.
Constant subroutine
    ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::MAX_DIR_SIZE redefined at /usr/share/perl/5.10/constant.pm line 115,  line 133 (#1)
[Thu Jul 30 09:39:37 2009] upload.pl: Constant subroutine ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::MAX_DIR_SIZE redefined at /usr/share/perl/5.10/constant.pm line 115,  line 133.
Constant subroutine
    ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::MAX_OPEN_TRIES redefined at /usr/share/perl/5.10/constant.pm line 115,  line 133 (#1)
[Thu Jul 30 09:39:37 2009] upload.pl: Constant subroutine ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::MAX_OPEN_TRIES redefined at /usr/share/perl/5.10/constant.pm line 115,  line 133.
Subroutine dir_size redefined at /home/stanislav/cgi/perl/upload.pl line 79,
     line 133 (#2)
[Thu Jul 30 09:39:37 2009] upload.pl: Subroutine dir_size redefined at /home/stanislav/cgi/perl/upload.pl line 79,  line 133.
Subroutine error redefined at /home/stanislav/cgi/perl/upload.pl line 90,
     line 133 (#2)
[Thu Jul 30 09:39:37 2009] upload.pl: Subroutine error redefined at /home/stanislav/cgi/perl/upload.pl line 90,  line 133.
Argument "" isn't numeric in numeric ge (>=) at
    /home/stanislav/cgi/perl/upload.pl line 62 (#4)
[Thu Jul 30 09:39:37 2009] -e: Argument "" isn't numeric in numeric ge (>=) at /home/stanislav/cgi/perl/upload.pl line 62.
Filehandle OUTPUT opened only for input at /home/stanislav/cgi/perl/upload.pl
    line 69 (#5)
[Thu Jul 30 09:39:37 2009] -e: Filehandle OUTPUT opened only for input at /home/stanislav/cgi/perl/upload.pl line 69.
Constant subroutine
    ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::UPLOAD_DIR redefined at /usr/share/perl/5.10/constant.pm line 115,  line 133 (#1)

为什么这些行在那里，有办法阻止它们吗？

发出此警告的代码（取自《CGI Programming with Perl》一书，其中包含一些 错误已修复）：

#!/usr/bin/perl
use strict;
use warnings;


use CGI;
use CGI::Carp;
#use diagnostics qw/-verbose/;

use Fcntl qw( :DEFAULT :flock );
use constant UPLOAD_DIR     => "/tmp/test_upload/";
use constant BUFFER_SIZE    => 16_384;
use constant MAX_FILE_SIZE  => 1_048_576;       # Limit each upload to 1 MB
use constant MAX_DIR_SIZE   => 100 * 1_048_576; # Limit total uploads to 100 MB
use constant MAX_OPEN_TRIES => 100;

$CGI::DISABLE_UPLOADS   = 0;
$CGI::POST_MAX          = MAX_FILE_SIZE;
my $q = new CGI;
$q->cgi_error and error( $q, "Error transferring file: " . $q->cgi_error );
my $file      = $q->param( "file" )     || error( $q, "No file received." );
my $filename  = $q->param( "filename" ) || error( $q, "No filename entered." );
my $fh        = $q->upload( "file" )     || error( $q, "Something is wrong with file handle." );
#my $fh        = $q->upload( $file );
my $buffer    = "";
if ( dir_size( UPLOAD_DIR ) + $ENV{CONTENT_LENGTH} > MAX_DIR_SIZE ) {
    error( $q, "Upload directory is full." );
}
# Allow letters, digits, periods, underscores, dashes
# Convert anything else to an underscore
$filename =~ s/[^\w.-]/_/g;
if ( $filename =~ /^(\w[\w.-]*)/ ) {
    $filename = $1;
}
else {
    error( $q, "Invalid file name; files must start with a letter or number." );
}
# Open output file, making sure the name is unique
until ( sysopen OUTPUT, UPLOAD_DIR . $filename, O_CREAT | O_EXCL ) {
    $filename =~ s/(\d*)(\.\w+)$/($1||0) + 1 . $2/e;
    $1 >= MAX_OPEN_TRIES and error( $q, "Unable to save your file." );
}
# This is necessary for non-Unix systems; does nothing on Unix
binmode $fh;
binmode OUTPUT;
# Write contents to output file
while ( read( $fh, $buffer, BUFFER_SIZE ) ) {
    print OUTPUT $buffer;
}
close OUTPUT;

if ( -T $fh ) {
    print $q->header("text/plain");
    seek $fh, 0, 0;
    map { print } ;
}

sub dir_size {
    my $dir = shift;
    my $dir_size = 0;

    # Loop through files and sum the sizes; doesn't descend down subdirs
    opendir DIR, $dir or die "Unable to open $dir: $!";
    while ( $_ = readdir DIR ) {
        $dir_size += -s "$dir/$_";
    }
    return $dir_size;
}
sub error {
    my( $q, $reason ) = @_;

    print $q->header( "text/html" ),
          $q->start_html( "Error" ),
          $q->h1( "Error" ),
          $q->p( "Your upload was not procesed because the following error ",
                 "occured: " ),
          $q->p( $q->i( $reason ) ),
          $q->end_html;
    exit;
}

此代码具有类似的输出： $ perl -e 'sub FOO () { 1 } BEGIN{ *FOO = sub () { 2 }; } print FOO;'

Constant subroutine main::FOO redefined at -e line 1.

我没有放置任何警告 qw/redefine/ 但它没有帮助。

Answer 1

AFAIK，只有当您修改脚本然后由 mod_perl 为符合内联条件的子例程重新编译脚本时，您才会收到这些警告。 当子例程重新编译时，如果它返回的值发生更改，则该新值将不会反映在先前内联的位置。

如果您更改了 BUFFER_SIZE 等值，则应重新启动 apache。

我还认为 mod_perl / Apache::Registry 意外关闭 与您的脚本有关。

Answer 2

据猜测，FOO 的第一个定义正在被优化掉。 在正文中用语句定义它，我想您会发现错误消失了。

<代码>
$ perl -e 'sub FOO () { print 1; } 开始{ *FOO = sub () { 2 }; } 打印 FOO;'