[CMake] Adding compile and build type tests to CMake/CTest

[paul]

On Thu, 2017-09-07 at 02:58 -0400, Edward Diener wrote:
> On 9/6/2017 11:39 PM, P F via CMake wrote:
> > 
> > The `add_test` function can run whatever command you want it to, including
> > compiling a target:
> > 
> > add_library(foo_compile_test STATIC EXCLUDE_FROM_ALL foo_compile_test.cpp)
> > add_test(NAME foo_compile_test
> >      COMMAND ${CMAKE_COMMAND} --build . --target foo_compile_test --config 
> > $<CONFIGURATION>
> >      WORKING_DIRECTORY ${CMAKE_BINARY_DIR})
> > 
> > Then you set cmake to expect failure:
> > 
> > set_tests_properties(foo_compile_test PROPERTIES WILL_FAIL TRUE)
> > 
> > You can also check for output instead of just expecting failure:
> > 
> > set_tests_properties(mytest PROPERTIES
> >    PASS_REGULAR_EXPRESSION "foo failed"
> > )
> > 
> > This is especially useful to make sure that the error is from the
> > static_assert message and not from another compile error.
> > 
> > Of course, cmake could provide a module which provides a function to do
> > this, which additionally could help workaround the caveats of this
> > approach. This is essentially what `bcm_test` in the boost cmake modules
> > do. > > Hopefully, in the future this module could be merged upstream into
> > cmake.
> It seems like a hack to have to build a CMake target, with the 
> add_library call, just to compile a source file as a test. 


I dont see how this is a hack. Cmake is target-oriented, if I want to control
the compile flags for this compile-test, I can do:

target_compile_options(foo_compile_test -Wall -Werror)

If it were builtin to cmake, how would the user set the compile options? It
seems cmake would need to add `target_*` based function for compile tests as
well. This seems bloated and inconsistent.