[CMake] Tests with assert and Release build type

[Magnus Therning]

Dave Flogeras writes:

> On Fri, Dec 18, 2015 at 9:55 AM, Magnus Therning <magnus at therning.org> wrote:
>>
>> I'm sure I'm not the first one to run into the conflict between a
>> desire to test the code shipped to customers and the desire to at the
>> same time define NDEBUG to make sure tests don't have their `assert`
>> turned into NOOPs.
>>
>> Is there some nice way of handling this?
>
> I've also wondered this. My solution of choice has always been to keep
> my tests in a subdirectory with a test header like you described:
>
> ....
> #fidef NDEBUG
>  #undef NDEBUG
>  #include <cassert> // or assert.h for C
>  #define NDEBUG
> #else
>  #include <cassert>
> #endif
> ....
>
> And include this in each of the unit tests. However, I have found
> sometimes this is not foolproof. In particular I recall on one version
> of OSX one of the system headers would undo this and make assert()
> disappear again, requiring me to play the #include shell game. I
> usually place my "test_assert.hpp" include after all others in the
> unit test, but this is brittle.
>
> I have always just left it as a "good enough" solution, but I too
> would love to hear if someone has a more robust solution.

I did a bit of testing and found that

1. CMAKE_C_FLAGS_* is, very irritatingly, *not* a list, so it's not easy
to remove '-DNDEBUG' from them in the CMakeLists.txt for the tests.

2. Compile options added by target_compile_options() are added *after*
CMAKE_C_FLAGS_* so I settled on using it to pass -UNDEBUG to gcc.

Far from nice, but it works for now (which feels quite typical for CMake).

/M

--
Magnus Therning              OpenPGP: 0x927912051716CE39
email: magnus at therning.org   jabber: magnus at therning.org
twitter: magthe               http://therning.org/magnus

If you can explain how you do something, then you're very very bad at
it.
     -- John Hopfield
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