[Bug c++/83428] Static initialization and struct with constexpr ctor

["redi at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83428

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |INVALID

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Aliaksei Kandratsenka from comment #3)
> constructor is defined after variable in this example. I am not sure this
> real bug.

Agreed. If we use Clang and add its require_constant_initialization attribute
to the variable definition it tells us:

83428.cc:20:54: error: variable does not have a constant initializer
 __attribute__((require_constant_initialization)) S2 objX;
                                                     ^~~~
83428.cc:20:17: note: required by 'require_constant_initialization' attribute
here
 __attribute__((require_constant_initialization)) S2 objX;
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
83428.cc:12:7: note: undefined constructor 'S1' cannot be used in a constant
expression
    : m_tabS1()
      ^
83428.cc:20:54: note: in call to 'S2()'
 __attribute__((require_constant_initialization)) S2 objX;
                                                     ^
83428.cc:3:15: note: declared here
    constexpr S1 ();
              ^
1 error generated.


If the S1::S1() constructor is defined before the definition of objX then Clang
doesn't warn and GCC doesn't use dynamic initialization.