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


On 17 February 2011 20:16, Marc Glisse <marc.glisse@inria.fr> wrote:
> On Thu, 17 Feb 2011, Jonathan Wakely wrote:
>
>> 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;
>
> Indeed, that's funny.
>
>> 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
>
> #include <utility>
> #include <array>
> struct A {
> ? ? ? ?A(){}
> };
> std::array< std::pair<int,A>, 2> x;

Great, thanks.  I've added it to the PR and marked it as a regression
(and confirmed it)


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