How to test that some code doesn't compile in

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Closed 8 years ago.

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Unit test compile-time error

I'm wondering if its possible to write a kind of unit test which will verify that a given code doesn't compile.

For example, I have a template class:

#include <boost/static_assert.hpp>
#include <boost/type_traits/is_base_of.hpp>

struct bar_base {};

template <typename T>
class foo 
{
    BOOST_STATIC_ASSERT(::boost::is_base_of<T, bar_base>::value);
};

So, the test should succeed with:

struct bar_derived : bar_base {};
foo<bar_derived> f;

but should fail with:

struct bar_other {};
foo<bar_other> f;

Any ideas how to achieve such a behaviour? (For now, I have to uncomment the failing code and verify manually that there are compile errors - I want to avoid that)

Answer 1

Boost does have compilation tests, and they do this by simply putting each of these tests into a single source-file and then try to compile each of these. Boost.Build supports special commands to run tests, which include testing if a file compiles or not.

Answer 2

The gist of it would be that you would run a normal "should fail" unittest, but instead of running your compiled program, you run a compiler on an example that should fail.

Eg on gtest, this would be a "death test" on the compiler. http://code.google.com/p/googletest/wiki/V1_6_AdvancedGuide#Death_Tests