Apache Module mod_so

Summary

On selected operating systems this module can be used to load modules into Apache HTTP Server at runtime via theDynamic Shared Object (DSO) mechanism, rather than requiring a recompilation.

On Unix, the loaded code typically comes from shared object files (usually with.so extension), on Windows this may either be the.so or.dll extension.

Topics

• Creating Loadable Modules for Windows

Directives

• LoadFile
• LoadModule

Bugfix checklist

• httpd changelog
• Known issues
• Report a bug

See also

• Comments

Creating Loadable Modules for Windows

The Apache httpd module API is unchanged between the Unix and Windows versions. Many modules will run on Windows with no or little change from Unix, although others rely on aspects of the Unix architecture which are not present in Windows, and will not work.

When a module does work, it can be added to the server in one of two ways. As with Unix, it can be compiled into the server. Because Apache httpd for Windows does not have theConfigure program of Apache httpd for Unix, the module's source file must be added to the ApacheCore project file, and its symbols must be added to theos\win32\modules.c file.

The second way is to compile the module as a DLL, a shared library that can be loaded into the server at runtime, using theLoadModule directive. These module DLLs can be distributed and run on any Apache httpd for Windows installation, without recompilation of the server.

To create a module DLL, a small change is necessary to the module's source file: The module record must be exported from the DLL (which will be created later; see below). To do this, add theAP_MODULE_DECLARE_DATA (defined in the Apache httpd header files) to your module's module record definition. For example, if your module has:

Replace the above with:

Note that this will only be activated on Windows, so the module can continue to be used, unchanged, with Unix if needed. Also, if you are familiar with.DEF files, you can export the module record with that method instead.

Now, create a DLL containing your module. You will need to link this against the libhttpd.lib export library that is created when the libhttpd.dll shared library is compiled. You may also have to change the compiler settings to ensure that the Apache httpd header files are correctly located. You can find this library in your server root's modules directory. It is best to grab an existing module .dsp file from the tree to assure the build environment is configured correctly, or alternately compare the compiler and link options to your .dsp.

This should create a DLL version of your module. Now simply place it in themodules directory of your server root, and use theLoadModule directive to load it.

LoadFileDirective

TheLoadFile directive links in the named object files or libraries when the server is started or restarted; this is used to load additional code which may be required for some module to work.Filename is either an absolute path or relative toServerRoot.

For example:

LoadFile "libexec/libxmlparse.so"

LoadModuleDirective

TheLoadModule directive links in the object file or libraryfilename and adds the module structure namedmodule to the list of active modules.Module is the name of the external variable of typemodule in the file, and is listed as theModule Identifier in the module documentation.

For example:

LoadModule status_module "modules/mod_status.so"

loads the named module from the modules subdirectory of the ServerRoot.