change cmake compiler from clang to g++ for mac

Question

I am working with a very inconvenient software, and it doesn't support clang. So, I am required to change my cmake compiler and as I read almost everywhere, and here How can I make CMake use GCC instead of Clang on Mac OS X?, I tried :

cmake -DCMAKE_CXX_COMPILER=/usr/bin/g++

However, I am still getting this error

CMake Error at CMakeLists.txt:59 (message):

GAMBIT does not support the Clang compiler. Please choose another compiler.

-- Configuring incomplete, errors occurred!

Any suggestion, please?

Try setting both the C and C++ compilers in the CMakeLists.txt file: SET(CMAKE_C_COMPILER /path/to/c/compiler) SET(CMAKE_CXX_COMPILER /path/to/cpp/compiler) — Scott Mudge, Sep 28 '17 at 14:29
Check if you have *real* gcc installed. AFAIR Xcode no longer ships *gcc*, and running `gcc` invokes `clang`. — el.pescado - нет войне, Sep 29 '17 at 10:13
I had two g++ one /usr/bin/g++ which was symlink of clang and the other one was /opt/local/bin/g++ which was my installed g++! — ShS, Sep 29 '17 at 18:33

Angew is no longer proud of SO · Accepted Answer · 2017-09-28T17:26:28.543

8

I've found setting environment variables CC and CXX before running CMake for the first time peferrable to messing with CMAKE_CXX_COMPILER. Also note that it's probably a good idea to set both. So get into an empty binary directory and run this:

CC=/usr/bin/gcc CXX=/usr/bin/g++ cmake ...

Also make sure that /usr/bin/gcc is really GCC and not e.g. a symlinked or otherwise disguised Clang (I believe such setup can exist in the MacOS world).

edited Sep 28 '17 at 17:26

answered Sep 28 '17 at 15:00

Angew is no longer proud of SO

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Also, relevant is that /usr/bin/gcc may not be gcc in the questioner's environment... – Jeff Garrett Sep 28 '17 at 15:20
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@JeffGarrett I've edited the answer, but my dev life and Apple do not intersect at all; can you please check that I've captured the concern correctly? – Angew is no longer proud of SO Sep 28 '17 at 15:37
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I don't have my MBP nearby. The following even claims it might be clang but not-a-symlink: https://stackoverflow.com/questions/20663695/mac-os-x-usr-bin-gcc-file – Jeff Garrett Sep 28 '17 at 16:23
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A comment here describes it as a clang shim: https://github.com/Homebrew/legacy-homebrew/issues/40374 – Jeff Garrett Sep 28 '17 at 16:23

valiano · Answer 2 · 2017-09-30T16:18:04.463

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You probably need to set CMAKE_C_COMPILER as well, that is:

cmake -DCMAKE_CXX_COMPILER=/usr/bin/g++ -DCMAKE_C_COMPILER=/usr/bin/gcc

Indeed, looking at Gambit source code, it seems it's mostly C.

Personally, I usually like to set both, just in case.

edited Sep 30 '17 at 16:18

answered Sep 29 '17 at 10:01

valiano

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my /usr/bin/g++ was actually a symlink to clang and the real address for my g++ was /opt/local/bin/g++! the default /usr/bin/g++ is the one coming with xcode – ShS Sep 29 '17 at 18:36

change cmake compiler from clang to g++ for mac

2 Answers2