title: How do I identify x86 vs. x86_64 at compile time in gcc?
body: <p>I want to compile part of my code only on x86 and x86_64 linux, but not s390 linux or others. How to use the macro define in C to achieve it? I know <strong>linux</strong> is to determine linux OS, and <strong>386</strong>, <strong>486</strong> and <strong>586</strong> to determine CPU architecture. Is there an easy macro define to determine x86 linux and x86_64 linux? Thanks </p>