Add testcase for PR4262.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90623 91177308-0d34-0410-b5e6-96231b3b80d8

test/FrontendC++/weak-external.cpp

@@ -0,0 +1,17 @@
+// RUN: %llvmgxx %s -S -emit-llvm -O2 -o - | not grep {_ZNSs12_S_constructIPKcEEPcT_S3_RKSaIcESt20forward_iterator_tag}
+// PR4262
+
+// The "basic_string" extern template instantiation declaration is supposed to
+// suppress the implicit instantiation of non-inline member functions. Make sure
+// that we suppress the implicit instantiation of non-inline member functions
+// defined out-of-line. That we aren't instantiating the basic_string
+// constructor when we shouldn't be. Such an instantiation forces the implicit
+// instantiation of _S_construct<const char*>. Since _S_construct is a member
+// template, it's instantiation is *not* suppressed (despite being in
+// basic_string<char>), so we would emit it as a weak definition.
+
+#include <stdexcept>
+
+void dummysymbol() {
+  throw(std::runtime_error("string"));
+}