[Bug libstdc++/88341] [9 Regression] taking norm() of complex variable fails to compile with -std=c++11

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88341

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2018-12-03
      Known to work|                            |8.2.0
           Assignee|unassigned at gcc dot gnu.org      |emsr at gcc dot gnu.org
     Ever confirmed|0                           |1
      Known to fail|                            |9.0

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Caused by r266416

The fix is simple:

--- a/libstdc++-v3/include/std/complex
+++ b/libstdc++-v3/include/std/complex
@@ -659,7 +659,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct _Norm_helper
     {
       template<typename _Tp>
-        static inline _GLIBCXX_CONSTEXPR _Tp _S_do_it(const complex<_Tp>& __z)
+        static inline _GLIBCXX20_CONSTEXPR _Tp _S_do_it(const complex<_Tp>&
__z)
         {
           const _Tp __x = __z.real();
           const _Tp __y = __z.imag();
@@ -671,7 +671,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct _Norm_helper<true>
     {
       template<typename _Tp>
-        static inline _GLIBCXX_CONSTEXPR _Tp _S_do_it(const complex<_Tp>& __z)
+        static inline _GLIBCXX20_CONSTEXPR _Tp _S_do_it(const complex<_Tp>&
__z)
         {
           //_Tp __res = std::abs(__z);
           //return __res * __res;