title: How can I figure out which architecture I'm compiling for in GCC?
body: <p>I want to write code that compiles easily for either 32 or 64 bit linux under gcc.  I guess I'm looking for something like</p>
  
  <pre><code>#ifdef IA32
  subl $0x4, %esp
  #endif
  
  #ifdef X86_64
  subl $0x4, %rsp
  #endif
  </code></pre>