[CMake] How to determine the compiler used outside of cmake

[Miller, Frank]

Update. The reason I didn’t have CMAKE_CXX_COMPILER in my cache is because I was doing a

  set(CMAKE_CXX_COMPILER /usr/bin/g++44 )

at the top of my root CMakeLists.txt. That preempts the set( CACHE ) call that project() does. My bad.

Frank

From: cmake-bounces at cmake.org [mailto:cmake-bounces at cmake.org] On Behalf Of Miller, Frank
Sent: Thursday, May 02, 2013 9:51 AM
To: m.hergarden at euphoria-it.nl
Cc: cmake at cmake.org
Subject: Re: [CMake] How to determine the compiler used outside of cmake

Interesting. I am running a very recent version (2.8.10.20130415) built from git. Perhaps the handling of CMAKE_CXX_COMPILER has changed recently.

I can’t believe I didn’t think to manually put it in the cache. That will work for me. Thanks.

As for the bigger problem I am solving... I have a wrapper script that drives the build. This is done to emulate a legacy build system and add some nice-to-haves. For example, the user can call the script from their source tree and it will call cmake/ninja in the proper binary tree. The default compiler to be used is hard coded into the CMakeLists.txt and I would like to have the script detect when the compiler changes and do a reconfigure automatically.

Now that I’m explaining the larger problem, I think I will have to put extra information in the cache to detect when the user manually overrides the default compiler. So I probably would have come around to your suggestion on my own.

Thanks again,

Frank

From: m.hergarden [mailto:m.hergarden at euphoria-it.nl]
Sent: Thursday, May 02, 2013 12:16 AM
To: Miller, Frank
Cc: cmake at cmake.org<mailto:cmake at cmake.org>
Subject: Re: [CMake] How to determine the compiler used outside of cmake

The compiler does show up in my cache: CMAKE_CXX_COMPILER:FILEPATH=/usr/bin/c++, but that doesn't solve your issue.
What is the bigger problem you are solving? If you really really need it in the cache, you can always write a variable yourself to make sure it's there.

Regards,
Micha

On 05/01/2013 09:56 PM, Miller, Frank wrote:
Greetings,

Given a configured build tree, I would like to determine the c++ compiler used without reconfiguring. I expected the CMAKE_CXX_COMPILER variable would be in the CMakeCache.txt but I was wrong. I tried to run a simple cmake script with ‘cmake -P’ and print the value of CMAKE_CXX_COMPILER but that does not work. I found the value in ‘CMakeFiles/2.8.10.20130415/CMakeCXXCompiler.cmake’, so I have a workaround, but that smells like the wrong solution. Does anyone know of a better way?

Thanks as always,

Frank



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