README.macosx - Perl under Mac OS X

This document briefly describes perl under Mac OS X.

The latest Perl (5.8.1-RC3 as of this writing) builds without changes under Mac OS X. Under the 10.3 Panther release, all self-tests pass, and all standard features are supported.

Earlier Mac OS X releases did not include a completely thread-safe libc, so threading is not fully supported. Also, earlier releases included a somewhat buggy libdb, so some of the DB_File tests are known to fail on those releases.

The default installation location for this release uses the traditional UNIX directory layout under /usr/local. This is the recommended location for most users, and will leave the Apple-supplied Perl and its modules undisturbed.

Using an installation prefix of '/usr' will result in a directory layout that mirrors that of Apple's default Perl, with core modules stored in '/System/Library/Perl/${version}', CPAN modules stored in '/Library/Perl/${version}', and the addition of '/Network/Library/Perl/${version}' to CW@INC for modules that are stored on a file server and used by many Macs.

Mac OS X ships with a dynamically-loaded libperl, but the default for this release is to compile a static libperl. The reason for this is pre-binding. Dynamic libraries can be pre-bound to a specific address in memory in order to decrease load time. To do this, one needs to be aware of the location and size of all previously-loaded libraries. Apple collects this information as part of their overall OS build process, and thus has easy access to it when building Perl, but ordinary users would need to go to a great deal of effort to obtain the information needed for pre-binding.

You can override the default and build a shared libperl if you wish (Configure ... -Duseshrlib), but the load time will be significantly greater than either the static library, or Apple's pre-bound dynamic library.

As of this writing, the latest Perl release that has been tested and approved for inclusion in the 10.3 Panther release of Mac OS X is 5.8.1 RC3. It is currently unknown whether the final 5.8.1 release will be made in time to be tested and included with Panther.

If the final release of Perl 5.8.1 is not made in time to be included with Panther, it is recommended that you wait for an official Apple update to the OS, rather than attempting to update it yourself. In most cases, if you need a newer Perl, it is preferable to install it in some other location, such as /usr/local or /opt, rather than overwriting the system Perl. The default location (no -Dprefix=... specified when running Configure) is /usr/local.

If you find that you do need to update the system Perl, there is one potential issue. If you upgrade using the default static libperl, you will find that the dynamic libperl supplied by Apple will not be deleted. If both libraries are present when an application that links against libperl is built, ld will link against the dynamic library by default. So, if you need to replace Apple's dynamic libperl with a static libperl, you need to be sure to delete the older dynamic library after you've installed the update.

Note that this is only an issue when updating from an older build of the same Perl version. If you're updating from (for example) 5.8.1 to 5.8.2, this issue won't affect you.

If you have installed extra libraries such as GDBM through Fink (in other words, you have libraries under /sw/lib), or libdlcompat to /usr/local/lib, you may need to be extra careful when running Configure to not to confuse Configure and Perl about which libraries to use. Being confused will show up for example as dyld errors about symbol problems, for example during make test. The safest bet is to run Configure as

    Configure ... -Uloclibpth -Dlibpth=/usr/lib

to make Configure look only into the system libraries. If you have some extra library directories that you really want to use (such as newer Berkeley DB libraries in pre-Panther systems), add those to the libpth:

    Configure ... -Uloclibpth -Dlibpth='/usr/lib /opt/lib'

The default of building Perl statically may cause problems with complex applications like Tk: in that case consider building shared Perl

    Configure ... -Duseshrplib

but remember that there's a startup cost to pay in that case (see above libperl and Prebinding).

Quite a bit has been written about MacPerl, the Perl distribution for Classic MacOS - that is, versions 9 and earlier of MacOS. Because it runs in environment that's very different from that of UNIX, many things are done differently in MacPerl. Modules are installed using a different procedure, Perl itself is built differently, path names are different, etc.

From the perspective of a Perl programmer, Mac OS X is more like a traditional UNIX than Classic MacOS. If you find documentation that refers to a special procedure that's needed for MacOS that's drastically different from the instructions provided for UNIX, the MacOS instructions are quite often intended for MacPerl on Classic MacOS. In that case, the correct procedure on Mac OS X is usually to follow the UNIX instructions, rather than the MacPerl instructions.

MacPerl ships with a number of modules that are used to access the classic MacOS toolbox. Many of these modules have been updated to use Mac OS X's newer Carbon toolbox, and are available from CPAN in the Mac::Carbon module.

There are two ways to use Cocoa from Perl. Apple's PerlObjCBridge module, included with Mac OS X, can be used by standalone scripts to access Foundation (i.e. non-GUI) classes and objects.

An alternative is CamelBones, a framework that allows access to both Foundation and AppKit classes and objects, so that full GUI applications can be built in Perl. CamelBones can be found on SourceForge, at <http://www.sourceforge.net/projects/camelbones/>.

Unfortunately it is not that difficult somehow manage to break one's Mac OS X Perl rather severely. If all else fails and you want to really, REALLY, start from scratch and remove even your Apple Perl installation (which has become corrupted somehow), the following instructions should do it. Please think twice before following these instructions: they are much like conducting brain surgery to yourself. Without anesthesia. We will not come to fix your system if you do this.

First, get rid of the libperl.dylib:

    # cd /System/Library/Perl/darwin/CORE
    # rm libperl.dylib

Then delete every .bundle file found anywhere in the folders:

    /System/Library/Perl
    /Library/Perl

You can find them for example by

    # find /System/Library/Perl /Library/Perl -name '*.bundle' -print

After this you can either copy Perl from your operating system CDs (you will need at least the /System/Library/Perl and /usr/bin/perl), or rebuild Perl from the source code with CWConfigure -Dprefix=/usr -Dusershrplib NOTE: the CW-Dprefix=/usr to replace the system Perl works much better with Perl 5.8.1 and later, in Perl 5.8.0 the settings were not quite right.

This README was written by Sherm Pendley <sherm@dot-app.org>. The Starting From Scratch recipe was contributed by John Montbriand <montbriand@apple.com>.

Last modified 2003-09-08.