Please improve test annotation

[Dave Abrahams]

The explicit-failures-markup for the optional_test_ref test is not informative enough to be useful to me. OK, so there's a compiler bug. How does it affect the usability of the library? What actually *is* the behavior of the library when I create optional<T&>? Is it just the address-of operator that's broken, or does the optional not actually store the reference as it should?

I'd appreciate it if you could improve this text.

[Dave Abrahams]

I think I understand the bug now (though the text should still be improved) and I have a suggestion to make: on those compilers where the bug exists, make the constructor in question explicit so that you can't mistakenly end up with a dangling reference. I did that by brute force in my local copy by specializing optional<V const&> and adding "explicit" to the ctor.

[Dave Abrahams]

Suggested new text:

This failure is caused by a compiler bug, and as far as we can tell, can't be worked around in the library, although we think the library might be made safer with respect to this bug.

Specifics: the following simple test fails when it should succeed.

 #include <cassert>

int const x = 0;
struct A
{
   A(int const& y)
   {
       assert(&x == &y);
   }
};

int main()
{
   A a(x);  // direct initialization works fine
   A b = x; // copy initialization causes x to be copied before it is bound
}

The possible safety enhancement would be to cause the constructor in question to be explicit for optional<T const&>; that would prevent copy initialization.

[Dean Michael Berris]

Dave, can you be a little more explicit as to which file this text should go in? I'm prepared to make a patch but I can't see where the expected failure annotation should be changed.

[anonymous]

It's at status/explicit-failures-markup.xml.

[Dean Michael Berris]

Replying to anonymous:

It's at status/explicit-failures-markup.xml.

Thanks for the pointer. I see two expected failure markups for optional_test_ref, one entry for msvc-6.5 and msvc-7.1 and another for the GCC family of compilers.

I'll add the above text in both entries and whoever will apply should do the right thing.

[Dean Michael Berris]

Proposed patch including the proposed text in the issue.

[Marshall Clow]

(In [67743]) Applied patch; refs #2294

[Marshall Clow]

Fix merged to release branch in [67792]