[CMake] infinite loop when trying to change the compiler in CMakeLists.txt

[Marcel Loose]

Another way to deal with this is to set CMAKE_C_COMPILER and
CMAKE_CXX_COMPILER *before* the first project() command. You could do
this in the main CMakeLists.txt file or in a separate CMake script file
that you include before the project() command.

In fact, this is what also happens when you do cross-compilation using a
tool-chain file. The tool-chain file is being read as the very first
file, before any CMakeLists.txt file is processed.

I don't know if doing things this way is considered good practice, but
I'm using it for our project to build with different compilers depending
on the name of the build directory.

Hope this helps,
Marcel Loose.

On Thu, 2009-11-05 at 11:36 -0700, Will Dicharry wrote:
> I think the best way to do that is with an initial cache via the -C
> flag to cmake.  Then you can set the initial CMAKE_<LANG>_COMPILER
> option in a CMake file and start with that file.
> 
> I currently don't do this, but I should.  At the moment I am doing
> this wrong by using the CMAKE_TOOLCHAIN_FILE variable and setting up
> the MPI wrapper compilers in there.  This is currently working for me,
> but it is the wrong way of doing it since the toolchain files should
> really only be used for cross compiling.
> 
> -- Will
> 
> On 11/05/2009 11:07 AM, bthomas at nexus.hu wrote: 
> > Dear All,
> > 
> > I am managing a CFD code where wish to set the CMAKE_C_COMPILER and CMAKE_CXX_COMPILER to openmpi 
> > wrappers.
> > 
> > So far i was using cmake 2.4.7 and in the CMakeLists.txt the following lines were working perfectly:
> > SET(CMAKE_C_COMPILER ${MPI_INSTALL_ROOT}/bin/mpicc )
> > SET(CMAKE_CXX_COMPILER ${MPI_INSTALL_ROOT}/bin/mpic++ )
> > 
> > Now that I changed to CMake 2.8.0 there is an infinite loop when trying to configure:
> > 
> > name at machine: ./deps/bin/cmake ../
> > -- The C compiler identification is GNU
> > -- The CXX compiler identification is GNU
> > -- Check for working C compiler: /usr/bin/gcc
> > -- Check for working C compiler: /usr/bin/gcc -- works
> > -- Detecting C compiler ABI info
> > -- Detecting C compiler ABI info - done
> > -- Check for working CXX compiler: /usr/bin/c++
> > -- Check for working CXX compiler: /usr/bin/c++ -- works
> > -- Detecting CXX compiler ABI info
> > -- Detecting CXX compiler ABI info - done
> > -- Configuring done
> > You have changed variables that require your cache to be deleted.
> > Configure will be re-run and you may have to reset some variables.
> > The following variables have changed:
> > CMAKE_C_COMPILER= /usr/bin/gcc
> > CMAKE_CXX_COMPILER= /usr/bin/c++
> > 
> > -- The C compiler identification is GNU
> > -- The CXX compiler identification is GNU
> > -- Check for working C compiler: /usr/bin/gcc
> > -- Check for working C compiler: /usr/bin/gcc -- works
> > -- Detecting C compiler ABI info
> > -- Detecting C compiler ABI info - done
> > -- Check for working CXX compiler: /usr/bin/c++
> > -- Check for working CXX compiler: /usr/bin/c++ -- works
> > -- Detecting CXX compiler ABI info
> > -- Detecting CXX compiler ABI info - done
> > -- Configuring done
> > You have changed variables that require your cache to be deleted.
> > Configure will be re-run and you may have to reset some variables.
> > The following variables have changed:
> > CMAKE_C_COMPILER= /usr/bin/gcc
> > CMAKE_CXX_COMPILER= /usr/bin/c++
> > 
> > ... and enters an infinite loop.
> > 
> > If I set the compilers via command line arguments, its fine.
> > But for easy-to-compile-by-the-users reason, I would like to set them in the CMakeLists.txt if
> > possible.
> > Can somebody help me out how to do this right?
> > 
> > The machine: Ubuntu, openmpi 1.3.3 with system gcc 4.4.1 behind
> > 
> > Thx:
> > Th
> > 
> > P.S.: I noted a bugfix in CMake 2.6.2 RC 2, may be connected:
> > "Fix infinite recursion bug with try-compile and change of compilers"
> > 
> > 
> > 
> > 
> >   
> > 
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