[Bug c/88568] [7 Regression] 'dllimport' no longer implies 'extern' in C

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88568

--- Comment #15 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 45894
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45894&action=edit
gcc9-pr88568-2.patch

Untested fix for that.  Apparently the C++ FE relies that static data members
have TREE_STATIC set, even when they are DECL_EXTERNAL, so this patch
essentially reverts the previous patch for static data members.

Unfortunately, like before, I have no way to test this on mingw/cygwin etc.