https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58541
Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Last reconfirmed| |2016-05-13 CC| |msebor at gcc dot gnu.org Blocks| |55004 Ever confirmed|0 |1 Known to fail| |4.9.3, 5.3.0, 6.1.0, 7.0 --- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> --- Confirmed. There is no requirement that the namespace-scope definition of a static constexpr class member say its constexpr. Today's trunk (7.0) fails with the following error. All supported versions of GCC fail to compile the test case. If I'm reading the logs right, the error was introduced in r166013. $ cat xx.cpp && gcc -S -Wall -Wextra -Wpedantic -o/dev/null -std=c++11 xx.cpp struct X { static constexpr const char x[] = "x"; }; const char X::x[]; xx.cpp:5:17: error: ‘constexpr’ needed for in-class initialization of static data member ‘const char X::x [2]’ of non-integral type [-fpermissive] const char X::x[]; ^ Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55004 [Bug 55004] [meta-bug] constexpr issues