c++: extern template and static data member [PR99066]

'extern template' should mean that the relevant symbols are never emitted.
But in this case we were assuming that DECL_EXTERNAL was already set on the
variable, so we just needed to clear DECL_NOT_REALLY_EXTERN.  Since
DECL_EXTERNAL was not set, we emitted a definition of npos.

gcc/cp/ChangeLog:

	PR c++/99066
	* pt.c (mark_decl_instantiated): Set DECL_EXTERNAL.

gcc/testsuite/ChangeLog:

	PR c++/99066
	* g++.dg/cpp0x/extern_template-6.C: New test.

2 files changed, 21 insertions, 1 deletions

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 1d19a59..396e622 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -24204,7 +24204,10 @@ mark_decl_instantiated (tree result, int extern_p)
   DECL_COMDAT (result) = 0;
 
   if (extern_p)
-    DECL_NOT_REALLY_EXTERN (result) = 0;
+    {
+      DECL_EXTERNAL (result) = 1;
+      DECL_NOT_REALLY_EXTERN (result) = 0;
+    }
   else
     {
       mark_definable (result);
diff --git a/gcc/testsuite/g++.dg/cpp0x/extern_template-6.C b/gcc/testsuite/g++.dg/cpp0x/extern_template-6.C
new file mode 100644
index 0000000..8aff3ae
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/extern_template-6.C
@@ -0,0 +1,17 @@
+// PR c++/99066
+// { dg-do compile { target c++11 } }
+
+template <typename a> struct basic_string {
+  static const int npos = 1;
+};
+template <typename a> const int basic_string<a>::npos;
+
+struct e { template <bool> int f() const; };
+
+template <bool> int e::f() const {
+  return basic_string<char>::npos;
+}
+
+extern template class basic_string<char>;
+
+// { dg-final { scan-assembler-not "_ZN12basic_stringIcE4nposE" } }