Compiling Universal Binaries under Mac OS X -- My Experience

I've spent a few months (on and mostly off) trying to get my C++/FLTK program, FamilyRelationsII, to build on my MacBook for both old and new Macs.

I was helped immensely by Mando Rodriguez and Diane Trout, both of whom contributed various snippets. Getting it all to play nice together was still painful enough that I think it's time to contribute something back to the lazyweb/googleplex.

Problem 1: Compiling FLTK cross-platform

I didn't actually keep notes for this, but basically I generated an X code project for FLTK and then selected "build cross-platform".

  1. In your fltk-1.1.x directory, generate an Xcode project with cmake -G Xcode .
  2. open FLTK.xcodeproj
  3. Select "FLTK" in the "Groups and Files" pane (left)
  4. Double-click, select 'Build'. Double-click on Architectures. Pick 'em both.
  5. Assuming the build works, you should see something like 'bin/Debug/libfltk.a'. These are the libraries you want.

I haven't figured out how to have them installed correctly yet; presumably that's yet another click away. At this point I just copy them into /usr/local/lib ;).

Problem 2: Compiling Xerces C++ cross-platform


./runConfigure -p macosx -n native -t native \
     -z -arch -z i386 -z -arch -z ppc \
     -l -arch -l i386 -l -arch -l ppc \
     -l -Wl,-syslibroot,/Developer/SDKs/MacOSX10.4u.sdk

for the default runConfigure command in the Xerces C documentation. Then make, make install.

(I guess I'll contact the Xerces C people about adding this to their docs...)

Problem 3(a): Linking /usr/local in properly

Because FLTK and Xerces-C++ are installed into /usr/local/lib by default, the -isysroot /Developer/SDKS/MacOSX10.4u.sdk stuff will not work unless you also do this:

% ln -fs /usr/local /Developer/SDKS/MacOSX10.4u.sdk/usr

Apparently you need to do this because -isysroot adds the /Developer/SDSKS/MacOSX10.4u.sdk/ prefix on to all library and header filename lookups; this lets Mac OS X know that universal libraries etc can be found under /usr/local as well.

Problem 3(b): Compiling your own code properly

The following CMake snippet (courtesy of Diane Trout) does the job well:

      "-isysroot /Developer/SDKS/MacOSX10.4u.sdk -arch i386 -arch ppc")

       "-Wl,-syslibroot,/Developer/SDKs/MacOSX10.4u.sdk -arch ppc -arch i386")


Then a standard 'cmake .' will put the right magic into your compilation flags.

Problem 3(c): Distributing dylibs with your Mac app

If you're planning to distribute your universal binary, and it depends on Xerces-C++ libraries, read this very helpful Qt doc; look esp at the Shared Libraries section. This worked beautifully for me.

Briefly, you need to use install_name_tool on both the Xerces-C++ dylib files and your compiled applications, to change the location in which they will be looking for libxerces-c.27.dylib. See my build-dist script diff for exactly what I do.

Conclusion: Double-checking stuff

If at any point you run into trouble compiling with both the '-arch ppc' and '-arch i386' flags, run 'file' on required libraries and other binaries to make sure they're universal:

% file FRII/app/FRII
FRII/app/FRII: Mach-O universal binary with 2 architectures
FRII/app/FRII (for architecture i386):  Mach-O executable i386
FRII/app/FRII (for architecture ppc):   Mach-O executable ppc

Well, I hope this helps someone! It was painful to learn, and AFAIK the correct Xerces-C++ incantations are not available elsewhere on the Web ;).

cheers, --titus

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