static_assert even if member is not instantiated

Question

When putting a with a hardcoded value, it is triggered even if the function it's in isn't instantiated. Is this behavior correct or do I misunderstand how static assert works?

#include <type_traits>
template <class T>
struct Helper
{
    static void do_something()
    {
        // Always fails, even when not instantiated.
        static_assert(false,
            "You must specialize this class to serialize Enums.");

        // Work around:
        static_assert(!std::is_same<T, T>::value,
            "You must specialize this class to serialize Enums.");
    }
};

Using: g++ (Ubuntu/Linaro 4.6.1-9ubuntu3) 4.6.1

Hmm, yea: is a dup.... Should I delete it? – nishantjr May 09 '14 at 07:56 — nishantjr, May 09 '14 at 07:56
@nishantjr: We'll close it, no prob. – MSalters May 09 '14 at 08:04 — MSalters, May 09 '14 at 08:04

score 0 · Answer 1 · answered May 09 '14 at 07:52

0

SFINAE works for function arguments and return type, not template parameters.

answered May 09 '14 at 07:52

Tony Delroy

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1

Sorry, don't thing SFINAE is relevant. Revised to give a more minimal example – nishantjr May 09 '14 at 07:54

score 0 · Answer 2 · edited May 23 '17 at 12:28

0

That is because "false" does not depend on the template in any way, for the compiler this code is sure to assert. There is similar thread

static_assert fails compilation even though template function is called nowhere

edited May 23 '17 at 12:28

Community

1
1

answered May 09 '14 at 07:55

static_assert even if member is not instantiated

2 Answers2