The Preprocessor

• Expands #define's, #ifdef's, etc.
• Uses /lib/cpp which we'll cover more later

Generating Object Files

Linking

• Resolves symbols between programs and creates executables
• Example from /mit/sipb-iap/unixsoftdev/examples/compilation/ex1:

  		cc -c hello.c
  		cc hello.o -o hello
  		hello
  

• Example: Linking with functions from elsewhere (ex2)

  		cc hello2.c     -o hello2 [fails]
  		cc hello2.c -lm -o hello2 [works]
  

  In this case, functions from the file /usr/lib/libm.a are needed for the sqrt function.

Compilation options

• For ensuring that code conforms to ANSI standard: -Wall -pedantic -ansi
• For optimization: -O3
• For debugging: -g (don't combine with -O)

Viewing symbols in an object file with nm

	% cc -c hello.c
	% nm hello.o
	00000000 t ___gnu_compiled_c
	         U ___main
	00000010 T _main
	         U _printf
	00000000 t gcc2_compiled.