Here's a useful tidbit that I thought I would share. If you want to find out
all of the built-in #define's that GCC gives you, try this:
touch dummy_file.c; gcc -E -dM dummy_file.c
On recent versions of GCC this will give you a list of all the predefined
macros. On older systems (I don't know how far back) you can try this:
gcc -dumpspecs
It's harder to read, but many of the platform-specific macros are in there.
