[PR c++/84497] ref to undefined tls init

https://gcc.gnu.org/ml/gcc-patches/2018-03/msg00209.html
	PR c++/84497
	* decl2.c (get_tls_init_fn): Check TYPE_HAS_TRIVIAL_DFLT too.

	PR c++/84497
	* g++.dg/cpp0x/pr84497.C: New.

Co-Authored-By: Jason Merrill <jason@redhat.com>
Co-Authored-By: Nathan Sidwell <nathan@acm.org>

From-SVN: r258244

gcc/cp/ChangeLog

+2018-03-05  Pádraig Brady  <P@draigBrady.com>
+	    Jason  Merrill  <jason@redhat.com>
+	    Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/84497
+	* decl2.c (get_tls_init_fn): Check TYPE_HAS_TRIVIAL_DFLT too.
+
 2018-03-03  Jason Merrill  <jason@redhat.com>
 
 	PR c++/84686 - missing volatile loads.

gcc/cp/decl2.c

@@ -3337,7 +3337,8 @@ get_tls_init_fn (tree var)
 	  /* If the variable is defined somewhere else and might have static
 	     initialization, make the init function a weak reference.  */
 	  if ((!TYPE_NEEDS_CONSTRUCTING (obtype)
-	       || TYPE_HAS_CONSTEXPR_CTOR (obtype))
+	       || TYPE_HAS_CONSTEXPR_CTOR (obtype)
+	       || TYPE_HAS_TRIVIAL_DFLT (obtype))
 	      && TYPE_HAS_TRIVIAL_DESTRUCTOR (obtype)
 	      && DECL_EXTERNAL (var))
 	    declare_weak (fn);

gcc/testsuite/ChangeLog

+2018-03-05  Pádraig Brady  <P@draigBrady.com>
+	    Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/84497
+	* g++.dg/cpp0x/pr84497.C: New.
+
 2018-03-05  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/84670

gcc/testsuite/g++.dg/cpp0x/pr84497.C

+// PR 84497 mismatch with thread constructor fn weakness
+// { dg-do compile { target c++11 } }
+// { dg-require-weak "" }
+
+struct Base
+{
+  int m;
+
+  Base() noexcept = default;  // trivial but not constexpr
+  ~Base() noexcept = default;
+};
+
+struct Derived : Base {};
+struct Container {
+  Base m;
+};
+
+#ifdef DEF
+// This bit for exposition only.
+// All items placed in .tbss
+// __tls_init simply sets __tls_guard
+// no aliases to __tls_init generated
+thread_local Base base_obj;
+thread_local Derived derived_obj;
+thread_local Container container_obj;
+#else
+// Erroneously created strong undef refs to
+// _ZTH11derived_obj, _ZTH13container_obj, _ZTH8base_obj
+extern thread_local Base base_obj;
+extern thread_local Derived derived_obj;
+extern thread_local Container container_obj;
+int main() { return !(&base_obj && &derived_obj && &container_obj);}
+#endif
+
+// { dg-final { scan-assembler ".weak\[ \t\]*_ZTH8base_obj" } }
+// { dg-final { scan-assembler ".weak\[ \t\]*_ZTH11derived_obj" } }
+// { dg-final { scan-assembler ".weak\[ \t\]*_ZTH13container_obj" } }