CODEWITHSUNDEEP
c++c++03
GBleaney
GBleaney

Reputation: 2196

C++03: How to get the return type of a function?

I have a struct that looks something like this:

struct Foo {
    typedef size_t result_type;

    template <class TYPE>
    result_type operator()(const TYPE& type) const;
};

I'm testing this struct and I want to be able to assert that the return type of the operator() is equal to size_t. If I could used C++11, I would go to decltype, however, I only have access to C++03. There are a few reasons I want to test something so seemingly obvious:

  1. My team have very rigorous testing policies where even things that can be verified visually must be tested
  2. Regression testing. I want to make sure this doesn't change in the future.
  3. This is a more simplified version of the code, things are a little more complicated and merit a bit more testing in the full version.

What options do I have to do this in C++03? I don't care if it is compile time or run time checking, just something that allows me to do an assert in my test driver.

Upvotes: 1

Views: 144

Answers (2)

Kenny Ostrom
Kenny Ostrom

Reputation: 5871

If you need to enforce binary compatibility of some data structures or messages, you may want to check the properties of the type rather than the type itself. These may change for what is called size_t in two different architectures.

assert(EXPECTED_SIZE == sizeof(result_type));
assert(EXPECTED_MIN == std::numeric_limits<result_type>::min());
assert(EXPECTED_MAX == std::numeric_limits<result_type>::max());

Upvotes: 0

Billy ONeal
Billy ONeal

Reputation: 106609

C++03 does not have a way of directly asking for the return type. You can deduce it with a function template (as Cody Gray suggests in comments) but for your testing purposes you don't need to do that. Just call your function under test and hand the result to an overload set like this:

template <typename AnythingElse>
void Foo(AnythingElse const&) { assert(false); }

void Foo(YourType const&) { /* pass */ }

That said, I would say testing the return type is probably a mistake -- testing an implementation detail instead of testing results.

Upvotes: 4

Related Questions