Compile time assertion

[Peter Kovacs]

Compile time assertion would be useful in some cases (instead of LEMON_ASSERT).

A possible solution is the following:

template <bool> struct STATIC_ASSERT_FAILURE;
template <> struct STATIC_ASSERT_FAILURE<true> {};
template<int x> struct static_assert_test{};

#define LEMON_COMPILE_ASSERT(x) \
   typedef static_assert_test<\
       sizeof(STATIC_ASSERT_FAILURE< (bool)( x ) >)>\
           _static_assert_typedef_

It could be used like that:

LEMON_COMPILE_ASSERT(numeric_limits<T>::is_integer);

[Alpar Juttner]

It would indeed be useful in some cases. How meaningful/understandable is the error message emitted by the compiler? For example how will it comment the line

LEMON_COMPILE_ASSERT(numeric_limits<double>::is_integer);

?

[Peter Kovacs]

boost/static_assert.h in the Boost library implements a solution. Maybe we should check it.

[Gábor Gévay]

C++11 has a keyword for this: ​http://en.cppreference.com/w/cpp/language/static_assert

The latest versions of GCC, Clang, ICC, MSVC all support it. But maybe an ifdef could hide it, if the compiler doesn't support it.