[Patch] [libstdc++] [constexpr] use macros in place of 'constexpr' to allow for disabling constexpr until fully supported by compiler

[Jonathan Wakely]

On 17 February 2011 19:02, Marc Glisse wrote:
> On Thu, 17 Feb 2011, Jonathan Wakely wrote:
>
>> On 17 February 2011 16:11, Paolo Carlini wrote:
>>>
>>> On 02/17/2011 03:06 PM, Adam Butcher wrote:
>>>>
>>>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46472
>
> [...]
>>
>> I don't much like the idea of patching the library and having to ship
>> those changes in 4.6.0 to workaround that bug (I think the two PRs are
>> the same issue.)  Especially as neither of those PRs shows code which
>> is affected by using constexpr in the library (I'm sure such code
>> exists, but the testcases provided don't show a library-related
>> problem.)
>
> Er, the one cited above shows an error with:
> std::array<std::pair<int,int>,2> myvar;

I beg to differ.  It shows code that certainly looks as though it was
derived from that, but I get no error for

#include <utility>
#include <array>
std::array<std::pair<int,int>,2> myvar;

Maybe the library has been changed to avoid the error since you
submitted the PR, but that's even more reason not to patch the
library.

I repeat the request for a testcase using libstdc++ which passed with
4.5 and fails with 4.6