Detect ICC vs GCC at compile time

Question

How to detect at compile time if I'm using gcc or icc?

(I was quite puzzled to find out that icc defines __GNUC__ -- and even __GNUC_MINOR__ and __GNUC_PATCHLEVEL__ ! why?)

Answer 1

We use

#ifdef __INTEL_COMPILER

to split icc off, assuming gcc as a default.