c++: add fixed testcase [PR109464]

Seems to be fixed by r15-521-g6ad7ca1bb90573.

	PR c++/109464

gcc/testsuite/ChangeLog:

	* g++.dg/template/explicit-instantiation8.C: New test.

(cherry picked from commit 58a9f3ded1a0ccc2c8b0a42f976950041734798e)

diff --git a/gcc/testsuite/g++.dg/template/explicit-instantiation8.C b/gcc/testsuite/g++.dg/template/explicit-instantiation8.C
new file mode 100644 (file)
index 0000000..92152a2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/explicit-instantiation8.C
@@ -0,0 +1,24 @@
+// PR c++/109464
+// { dg-do compile { target c++11 } }
+
+template<typename T>
+struct shallow
+ {
+   int len;
+   constexpr shallow() : len(0) { }
+  };
+
+template<typename T>
+struct use_shallow
+  {
+   static constexpr shallow<T> s_zstr = { };
+   static_assert(s_zstr.len == 0, "");
+  };
+
+extern template struct shallow<char>;
+extern template struct use_shallow<char>;
+
+template struct shallow<char>;
+template struct use_shallow<char>;
+
+// { dg-final { scan-assembler "_ZN7shallowIcEC2Ev" } }