---
name: "Apache2::compat"
section: "3pm"
platform: "linux"
package: "libapache2-mod-perl2"
version: "2.0.13-2+b2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Apache2::compat"
---

# Apache2::compat(3pm)

## NAME

Apache2::compat -- 1.0 backward compatibility functions deprecated in 2.0

## Synopsis

```
  # either add at the very beginning of startup.pl
  use Apache2::compat;
  # or httpd.conf
  PerlModule Apache2::compat
  # override and restore compat functions colliding with mp2 API
  Apache2::compat::override_mp2_api('Apache2::Connection::local_addr');
  my ($local_port, $local_addr) = sockaddr_in($c->local_addr);
  Apache2::compat::restore_mp2_api('Apache2::Connection::local_addr');
```

## Description

`"Apache2::compat"` provides mod\_perl 1.0 compatibility layer and can be used to smooth the transition process to mod\_perl 2.0.

It includes functions that have changed their API or were removed in mod\_perl 2.0. If your code uses any of those functions, you should load this module at the server startup, and everything should work as it did in 1.0. If it doesn't please report the bug, but before you do that please make sure that your code does work properly under mod\_perl 1.0.

However, remember, that it's implemented in pure Perl and not C, therefore its functionality is not optimized and it's the best to try to port your code not to use deprecated functions and stop using the compatibility layer.

## Compatibility Functions Colliding with mod\_perl 2.0 API

Most of the functions provided by Apache2::compat don't interfere with mod\_perl 2.0 API. However there are several functions which have the same name in the mod\_perl 1.0 and mod\_perl 2.0 API, accept the same number of arguments, but either the arguments themselves aren't the same or the return values are different. For example the mod\_perl 1.0 code:

```
  require Socket;
  my $sockaddr_in = $c->local_addr;
  my ($local_port, $local_addr) = Socket::sockaddr_in($sockaddr_in);
```

should be adjusted to be:

```
  require Apache2::Connection;
  require APR::SockAddr;
  my $sockaddr = $c->local_addr;
  my ($local_port, $local_addr) = ($sockaddr->port, $sockaddr->ip_get);
```

to work under mod\_perl 2.0.

As you can see in mod\_perl 1.0 API **local\_addr()** was returning a SOCKADDR\_IN object (see the Socket perl manpage), in mod\_perl 2.0 API it returns an `"APR::SockAddr"` object, which is a totally different beast. If Apache2::compat overrides the function `local_addr()` to be back-compatible with mod\_perl 1.0 API. Any code that relies on this function to work as it should under mod\_perl 2.0 will be broken. Therefore the solution is not to override `local_addr()` by default. Instead a special API is provided which overrides colliding functions only when needed and which can be restored when no longer needed. So for example if you have code from mod\_perl 1.0:

```
  my ($local_port, $local_addr) = Socket::sockaddr_in($c->local_addr);
```

and you aren't ready to port it to to use the mp2 API:

```
  my ($local_port, $local_addr) = ($c->local_addr->port,
                                   $c->local_addr->ip_get);
```

you could do the following:

```
  Apache2::compat::override_mp2_api('Apache2::Connection::local_addr');
  my ($local_port, $local_addr) = Socket::sockaddr_in($c->local_addr);
  Apache2::compat::restore_mp2_api('Apache2::Connection::local_addr');
```

Notice that you need to restore the API as soon as possible.

Both `override_mp2_api()` and `restore_mp2_api()` accept a list of functions to operate on.

### Available Overridable Functions

At the moment the following colliding functions are available for overriding:

- Apache2::RequestRec::notes

  - Apache2::RequestRec::filename

  - Apache2::RequestRec::finfo

  - Apache2::Connection::local\_addr

  - Apache2::Connection::remote\_addr

  - Apache2::Util::ht\_time

  - Apache2::Module::top\_module

  - Apache2::Module::get\_config

  - APR::URI::unparse

  ## Use in CPAN Modules

The short answer: **Do not use** `"Apache2::compat"` in CPAN modules.

The long answer:

`"Apache2::compat"` is useful during the mod\_perl 1.0 code porting. Though remember that it's implemented in pure Perl. In certain cases it overrides mod\_perl 2.0 methods, because their API is very different and doesn't map 1:1 to mod\_perl 1.0. So if anything, not under user's control, loads `"Apache2::compat"` user's code is forced to use the potentially slower method. Which is quite bad.

Some users may choose to keep using `"Apache2::compat"` in production and it may perform just fine. Other users will choose not to use that module, by porting their code to use mod\_perl 2.0 API. However it should be users' choice whether to load this module or not and not to be enforced by CPAN modules.

If you port your CPAN modules to work with mod\_perl 2.0, you should follow the porting Perl and XS module guidelines.

Users that are stuck with CPAN modules preloading `"Apache2::compat"`, can prevent this from happening by adding

```
  $INC{'Apache2/compat.pm'} = __FILE__;
```

at the very beginning of their *startup.pl*. But this will most certainly break the module that needed this module.

## API

You should be reading the mod\_perl 1.0 API docs for usage of the methods and functions in this package, since what this module is doing is providing a backwards compatibility and it makes no sense to duplicate documentation.

Another important document to read is: Migrating from mod\_perl 1.0 to mod\_perl 2.0 which covers all mod\_perl 1.0 constants, functions and methods that have changed in mod\_perl 2.0.

## See Also

mod\_perl 2.0 documentation.

## Copyright

mod\_perl 2.0 and its core modules are copyrighted under The Apache Software License, Version 2.0.

## Authors

The mod\_perl development team and numerous contributors.