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?)

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

score 19 · Accepted Answer · answered Apr 20 '11 at 21:24

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We use

#ifdef __INTEL_COMPILER

to split icc off, assuming gcc as a default.

answered Apr 20 '11 at 21:24

Dirk Eddelbuettel

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score 9 · Answer 2 · answered Apr 20 '11 at 21:25

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I believe you could check for __INTEL_COMPILER according to this.

answered Apr 20 '11 at 21:25

cnicutar

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This is more transparent https://www.boost.org/doc/libs/1_59_0/boost/config/compiler/intel.hpp – alfC Mar 11 '21 at 02:24

score 1 · Answer 3 · answered Nov 29 '12 at 11:56

You can make the processor output the defined macros in the preprocessor output and look for a macro that suits you. You can generated the preprocessor output like this:

icc  -dM -E -o foo.P foo.c

Then look at foo.P (since it is a text file). In my case, I found icc defined an __ICC macro with the version of the compiler. It didn't define any __INTEL_COMPILER though.

score 1 · Answer 4 · answered Apr 20 '11 at 21:56

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

answered Apr 20 '11 at 21:56

R.. GitHub STOP HELPING ICE

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You make it sound like it is a) his fault, b) not a good thing to do without giving any explanation. – Zulan Feb 04 '16 at 08:24
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Another way to put this is that ICC implements the GNU dialect of C (and C++), and that's what the presence of `__GNUC__` indicates. It doesn't mean that the compiler is the GNU implementation of the GNU C language. – Peter Cordes Nov 08 '16 at 18:16

score 1 · Answer 5 · answered Apr 21 '11 at 08:18

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.

Detect ICC vs GCC at compile time

5 Answers5