Things I’ve learned recently:

• Using hg log on a file that was removed will not list the revision in which the file was removed. You want hg log --removed.
• Waist Watcher sodas are sweetened with Splenda, but don’t have the metallic taste that some other diet sodas do. I especially like the Citrus Frost (grapefruit) flavor. It’s like Fresca without the hidden Aspartame. (I have bad digestive reactions to Apartame.)
• Linking libxul on my Linux machine takes between 3 and 10 seconds, but apparently this is unusual. Several other people have reported link times that can range into the minutes. I recommend buying as much RAM as you can: if your entire object directory fits in the filesystem memory cache, build speed is much faster.
• When Microsoft Visual C++ mangles function symbols, the return type is encoded in the mangled name. When GCC mangles names, the return type is not encoded:
  

  	GCC	MSVC
  int testfunc(int)	_Z8testfunci	?testfunc@@YAHH@Z
  void testfunc(int)	_Z8testfunci	?testfunc@@YAXH@Z

  This means that separate functions in different translation units may not differ only by return type. We found this trying to combine the Chromium IPC code with Mozilla: const std::string& EmptyString() and const nsAFlatString& EmptyString() differ only by return type. On Windows this links correctly, but on Linux this causes multiple-definition errors.