XPCOM and OS X

What I had to do to get an XPCOM component written in C++ compiled and linked on OS X

1. Install Xcode

2. Install Fink

3. At command prompt
cd /sw/bin;
sudo ./apt-get install glib
sudo ./apt-get install libIDL2
sudo cp libIDL-config-2 libIDL-config

4. Download the source of the Firefox version you'll be developing for. The only steps I had to perform that weren't mentioned on
http://developer.mozilla.org/en/docs/Mac_OS_X_Build_Prerequisites
was to add the following directory to my path
/sw/bin

5. change to directory to which Firefox source was downloaded and run the following commands
cp ./obj-ff/dist/bin/libxpcom_core.dylib ./obj-ff/dist/sdk/bin
cp ./obj-ff/dist/bin/libplds4.dylib ./obj-ff/dist/sdk/bin
cp ./obj-ff/dist/bin/libplc4.dylib ./obj-ff/dist/sdk/bin

6. Follow the steps give in
http://rcrowley.org/2007/07/17/cross-platform-xpcom-a-howto/
with Makefile looking like this:

GECKO_SDK := /obj-ff/dist/sdk

DEFINE := -DXP_UNIX -DXP_MACOSX
all: xpt dylib
xpt:
$(GECKO_SDK)/bin/xpidl -m header -I$(GECKO_SDK)/idl foo.idl
$(GECKO_SDK)/bin/xpidl -m typelib -I$(GECKO_SDK)/idl foo.idl
impl:
g++ -w -c -o foo_impl.o -I $(GECKO_SDK)/include $(DEFINE) foo_impl.cpp
module:
g++ -w -c -o foo_module.o -I $(GECKO_SDK)/include $(DEFINE) foo_module.cpp
dylib: impl module
g++ -dynamiclib -o foo.dylib foo_impl.o foo_module.o -L$(GECKO_SDK)/lib \
-L$(GECKO_SDK)/bin -Wl,-executable_path,$(GECKO_SDK)/bin \
-lxpcomglue_s -lxpcom -lnspr4
clean:
rm *.o
rm foo.h
rm foo.xpt
rm foo.dylib

7. Run make. Hopefully, it should work.