[cmake] Use the compiler clad is built for if compiling benchmarks an…

…d tests.

We need to attach the clad plugin to the compiler invocations in order to
either benchmark or test clad's infrastructure. The best way I could find is by
setting/resetting the CMAKE_CXX_COMPILER variable which is a hack that works.
Note that we do not have a cmake guarantee that will work but since that's in
the core of our testing infrastructure we will find out quickly if, when and
where it breaks.

CMakeLists.txt

@@ -295,8 +295,20 @@ if (CLAD_INCLUDE_DOCS)
   add_subdirectory(docs)
 endif()
 
+
 if (NOT CLAD_BUILD_STATIC_ONLY)
   include(AddClad)
+
+  if (CLAD_ENABLE_BENCHMARKS)
+    include(GoogleBenchmark)
+  endif(CLAD_ENABLE_BENCHMARKS)
+
+  # Change the default compiler to the clang which we run clad upon. Our unittests
+  # need to use a supported by clad compiler. Note that's a huge hack and it is
+  # not guaranteed to work with cmake.
+  set(stored_cxx_compiler ${CMAKE_CXX_COMPILER})
+  set(CMAKE_CXX_COMPILER ${LLVM_TOOLS_BINARY_DIR}/clang)
+
   add_subdirectory(unittests)
   add_subdirectory(test)
   add_subdirectory(demos/ErrorEstimation/CustomModel)
@@ -307,6 +319,8 @@ if (NOT CLAD_BUILD_STATIC_ONLY)
     add_subdirectory(benchmark)
   endif(CLAD_ENABLE_BENCHMARKS)
 
+  # Restore the default compiler.
+  set(CMAKE_CXX_COMPILER ${stored_cxx_compiler})
 endif()
 
 # Workaround for MSVS10 to avoid the Dialog Hell

benchmark/CMakeLists.txt

@@ -1,8 +1,6 @@
 set(CTEST_BUILD_NAME ${ROOT_ARCHITECTURE}-${CMAKE_BUILD_TYPE})
 enable_testing()
 
-include(GoogleBenchmark)
-
 CB_ADD_GBENCHMARK(Simple Simple.cpp)
 CB_ADD_GBENCHMARK(AlgorithmicComplexity AlgorithmicComplexity.cpp)
 CB_ADD_GBENCHMARK(ArrayExpressionTemplates ArrayExpressionTemplates.cpp)

cmake/modules/AddClad.cmake

@@ -10,9 +10,6 @@ string(REPLACE "/" "" CURRENT_REPO_COMMIT ${CURRENT_REPO_COMMIT})
 set_property(DIRECTORY APPEND PROPERTY
              CMAKE_CONFIGURE_DEPENDS "${CMAKE_SOURCE_DIR}/.git/HEAD")
 
-# Change the default compiler to the clang which we run clad upon.
-set(CMAKE_CXX_COMPILER ${LLVM_TOOLS_BINARY_DIR}/clang)
-
 #-------------------------------------------------------------------------------
 # function ENABLE_CLAD_FOR_EXECUTABLE(<executable>
 #   DEPENDS dependencies...

unittests/CMakeLists.txt

@@ -11,6 +11,7 @@ endif()
 # Will compile the list of files together and link against clad.
 # Produces a binary named 'basename(test_dirname)'.
 function(add_clad_unittest test_dirname)
+
   add_unittest(CladUnitTests ${test_dirname} ${ARGN})
 
   # Remove the llvm_gtest_* coming from add_unittest.
@@ -32,4 +33,3 @@ function(add_clad_unittest test_dirname)
 endfunction()
 
 add_subdirectory(Basic)
-