Detect ICC vs GCC at compile time?

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(I was quite puzzled to find out that icc defines __GNUC__ -- and even __GNUC_MINOR__ and __GNUC_PATCHLEVEL__! Why? ) c++ c gcc icc predefined-macro link|improve this question edited Apr 20 '11 at 21:39osgx13.1k32081 asked Apr 20 '11 at 21:21Znorg353.

2 Clang also defines these, they are for compatibility purposes: you can just replace the gcc command with icc, with the exact same options, without anything breaking (or that's the idea). – rubenvb Apr 20 '11 at 21:31.

We use #ifdef __INTEL_COMPILER to split icc off, assuming gcc as a default.

3 Handy link time: predef.sourceforge.net/precomp.html – Cat Plus Plus Apr 20 '11 at 21:25.

I believe you could check for __INTEL_COMPILER according to this.

The reason ICC defines __GNUC__ etc. is because of code like yours that is inspecting compiler-specific macros and expects to see them...

Traditionally, compilers have defined a symbol of their own as well as their version as preprocessor symbols so that the code could be adapted (generally to work around bugs or specificities). CLang has introduced a mechanism I had not seen so far, under the form of the __has_feature query. It does not replace the "work around bugs" practices (which is why CLang still exposes specific symbols) but allows a more natural style for querying the compiler capacities.

I don't know if other compilers plan on defining such a facility.

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