[Bug c++/51675] [C++11][4.7 Regression] Cannot create constexpr unions

["nephatrine at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51675

Daniel Wolf <nephatrine at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |nephatrine at gmail dot com

--- Comment #4 from Daniel Wolf <nephatrine at gmail dot com> 2012-02-03 06:24:12 UTC ---
(In reply to comment #1)
> More information: initializing in the constructor doesn't work, either.
> 
> union foo
> {
>     int x;
>     short y;
> 
>     constexpr foo() : x(0) { }
> };
> 
> Also does not compile.

This code does not compile with the latest trunk.

error: uninitialized member 'foo::y' in 'constexpr' constructor

> union foo
> {
>     int x = 0;
>     short y;
> 
>     constexpr foo() = default;
> };

This does compile... but I cannot instantiate a constexpr foo. Adding this
line:

constexpr foo test;

Gives me the following output:

g++-4.7 -std=gnu++11 -o Test.o -c Test.cpp
Test.cpp: In function 'int main(int, char**)':
Test.cpp:35:16: error: uninitialized const 'test' [-fpermissive]
Test.cpp:6:7: note: 'const union foo' has no user-provided default constructor
Test.cpp:11:15: note: constructor is not user-provided because it is explicitly
defaulted in the class body
Test.cpp:9:11: note: and the implicitly-defined constructor does not initialize
'short int foo::y'
Test.cpp:35:16: error: 'constexpr foo::foo()' called in a constant expression
Test.cpp:11:15: note: 'constexpr foo::foo()' is not usable as a constexpr
function because:

Yeah... the last line ends with a colon but no followup. Might want to reopen
this...