Add some reproducers for issues found when developing the location-wrappers patch

diff --git a/gcc/testsuite/g++.dg/wrappers/README b/gcc/testsuite/g++.dg/wrappers/README
new file mode 100644
index 0000000..9cba970
--- /dev/null
+++ b/gcc/testsuite/g++.dg/wrappers/README
@@ -0,0 +1,2 @@ 
+This directory contains reproducers for issues seen when adding location
+wrapper nodes to the C++ frontend (ICEs and behavior changes).
diff --git a/gcc/testsuite/g++.dg/wrappers/alloc.C b/gcc/testsuite/g++.dg/wrappers/alloc.C
new file mode 100644
index 0000000..e004470
--- /dev/null
+++ b/gcc/testsuite/g++.dg/wrappers/alloc.C
@@ -0,0 +1,43 @@ 
+// { dg-do compile { target c++11 } }
+
+template<typename _Default, typename _AlwaysVoid, template<typename...> class _Op, typename... _Args>
+struct __detector
+{
+  using type = _Op<_Args...>;
+};
+template<typename _Default, template<typename...> class _Op, typename... _Args>
+using __detected_or = __detector<_Default, void, _Op, _Args...>;
+template<typename _Default, template<typename...> class _Op, typename... _Args>
+using __detected_or_t = typename __detected_or<_Default, _Op, _Args...>::type;
+template<typename _Alloc>
+struct allocator_traits {
+  template<typename _Tp>
+  using __pointer = typename _Tp::pointer;
+  using pointer = __detected_or_t<typename _Alloc::value_type*, __pointer, _Alloc>;
+};
+template<typename _Storage_policy>
+struct _Pointer_adapter {
+  typedef typename _Storage_policy::element_type element_type;
+  typedef element_type& reference;
+};
+template<typename _Tp>
+inline _Tp* addressof(_Tp& __r); // { dg-warning "used but never defined" }
+template<typename _Alloc>
+struct __allocated_ptr {
+  __allocated_ptr()
+  {
+    using pointer = typename allocator_traits<_Alloc>::pointer;
+    typename _Pointer_adapter<pointer>::reference __r = *(int*)0;
+    addressof(__r);
+  }
+};
+template<typename _Tp>
+struct _Std_pointer_impl {
+  typedef _Tp element_type;
+};
+template<typename Tp>
+struct CustomPointerAlloc {
+  typedef Tp value_type;
+  typedef _Pointer_adapter<_Std_pointer_impl<Tp>> pointer;
+};
+__allocated_ptr<CustomPointerAlloc<int>> __guard_ptr;
diff --git a/gcc/testsuite/g++.dg/wrappers/cow-istream-string.C b/gcc/testsuite/g++.dg/wrappers/cow-istream-string.C
new file mode 100644
index 0000000..23b0585
--- /dev/null
+++ b/gcc/testsuite/g++.dg/wrappers/cow-istream-string.C
@@ -0,0 +1,15 @@ 
+template<typename _CharT>
+struct basic_string {
+  static const _CharT _S_terminal;
+  static void assign(const _CharT& __c2);
+  void _M_set_length_and_sharable() {
+    assign(_S_terminal);
+  }
+};
+
+template<typename _CharT>
+const _CharT basic_string<_CharT>::_S_terminal = _CharT();
+
+void getline(basic_string<char>& __str) {
+  __str._M_set_length_and_sharable();
+}
diff --git a/gcc/testsuite/g++.dg/wrappers/cp-stdlib.C b/gcc/testsuite/g++.dg/wrappers/cp-stdlib.C
new file mode 100644
index 0000000..d29585f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/wrappers/cp-stdlib.C
@@ -0,0 +1,117 @@ 
+/* At one time this triggered ICEs with location wrapper nodes,
+   apparently requiring error-recovery (hence the various syntax
+   errors in this file.  */
+
+// { dg-excess-errors "expected to be full of errors, but not an ICE" }
+
+namespace std
+{
+  inline namespace __cxx11 __attribute__((__abi_tag__ ("cxx11"))) { }
+}
+namespace __gnu_cxx __attribute__ ((__visibility__ ("default")))
+{
+  template<typename _Tp>
+    class new_allocator
+    {
+      typedef _Tp value_type;
+    };
+}
+namespace std
+{
+  template<typename _Tp>
+    using __allocator_base = __gnu_cxx::new_allocator<_Tp>;
+}
+namespace std __attribute__ ((__visibility__ ("default")))
+{
+    {
+    };
+  template<typename _Tp>
+    class allocator : public __allocator_base<_Tp>
+    {
+    };
+  template<typename _Alloc>
+    struct allocator_traits : __allocator_traits_base
+    {
+    };
+  template<typename _Tp>
+    struct allocator_traits<allocator<_Tp>>
+    {
+      using allocator_type = allocator<_Tp>;
+      template<typename _Up>
+ using rebind_alloc = allocator<_Up>;
+      allocate(allocator_type& __a, size_type __n)
+    };
+}
+namespace __gnu_cxx __attribute__ ((__visibility__ ("default")))
+{
+template<typename _Alloc, typename = typename _Alloc::value_type>
+  struct __alloc_traits
+  : std::allocator_traits<_Alloc>
+  {
+    typedef std::allocator_traits<_Alloc> _Base_type;
+    template<typename _Tp>
+      struct rebind
+      { typedef typename _Base_type::template rebind_alloc<_Tp> other; };
+  };
+{
+    {
+ }
+ }
+    }
+    {
+ {
+    }
+}
+namespace std __attribute__ ((__visibility__ ("default")))
+{
+    struct char_traits;
+namespace __cxx11 {
+  template<typename _CharT, typename _Traits = char_traits<_CharT>,
+           typename _Alloc = allocator<_CharT> >
+    class basic_string;
+    }
+}
+namespace std __attribute__ ((__visibility__ ("default")))
+{
+namespace __cxx11 {
+  template<typename _CharT, typename _Traits, typename _Alloc>
+    class basic_string
+    {
+      typedef typename __gnu_cxx::__alloc_traits<_Alloc>::template
+ rebind<_CharT>::other _Char_alloc_type;
+      typedef __gnu_cxx::__alloc_traits<_Char_alloc_type> _Alloc_traits;
+    public:
+      {
+   {
+   }
+      }
+      operator=(const basic_string& __str)
+      {
+   {
+       {
+    {
+      const auto __len = __str.size();
+      auto __alloc = __str._M_get_allocator();
+      auto __ptr = _Alloc_traits::allocate(__alloc, __len + 1);
+    }
+       }
+   }
+      }
+      {
+      }
+      size() const noexcept
+     }
+namespace filesystem
+{
+  class path
+  {
+    typedef char value_type;
+    typedef std::basic_string<value_type> string_type;
+      {
+    }
+    string_type _M_pathname;
+  };
+  class directory_entry
+  {
+    void assign(const filesystem::path& __p) { _M_path = __p; }
+    filesystem::path _M_path;
diff --git a/gcc/testsuite/g++.dg/wrappers/sanitizer_coverage_libcdep_new.C b/gcc/testsuite/g++.dg/wrappers/sanitizer_coverage_libcdep_new.C
new file mode 100644
index 0000000..2be140b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/wrappers/sanitizer_coverage_libcdep_new.C
@@ -0,0 +1,22 @@ 
+namespace __sanitizer {
+
+enum FileAccessMode {
+  RdOnly,
+  WrOnly,
+  RdWr
+};
+
+int OpenFile(const char *filename, int mode,
+	     int *errno_p);
+}
+
+using namespace __sanitizer;
+
+namespace __sancov {
+
+static int OpenFile(const char* path) {
+  int err;
+  int fd = OpenFile(path, WrOnly, &err);
+  return fd;
+}
+}
diff --git a/gcc/testsuite/g++.dg/wrappers/wrapper-around-type-pack-expansion.C b/gcc/testsuite/g++.dg/wrappers/wrapper-around-type-pack-expansion.C
new file mode 100644
index 0000000..5072d1a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/wrappers/wrapper-around-type-pack-expansion.C
@@ -0,0 +1,50 @@ 
+// { dg-do compile { target c++11 } }
+
+typedef long unsigned int size_t;
+
+template<typename _Tp>
+struct remove_reference {};
+
+template<typename _Tp>
+constexpr _Tp&&
+forward(typename remove_reference<_Tp>::type& __t) noexcept
+{
+}
+
+struct __allocator_traits_base {
+  template<typename _Tp, typename _Up, typename = void>
+  struct __rebind
+  {
+    using type = typename _Tp::template rebind<_Up>::other;
+  };
+};
+
+template<typename _Alloc, typename _Up>
+using __alloc_rebind = typename __allocator_traits_base::template __rebind<_Alloc, _Up>::type;
+
+template<typename _Alloc>  struct allocator_traits {
+  template<typename _Tp>  using rebind_alloc = __alloc_rebind<_Alloc, _Tp>;
+  template<typename _Tp, typename... _Args>
+  static auto construct(_Alloc& __a, _Tp* __p, _Args&&... __args)
+    -> decltype(_S_construct(__a, __p, forward<_Args>(__args)...))  {   }
+};
+
+template<typename _Alloc, typename = typename _Alloc::value_type>
+struct __alloc_traits    : allocator_traits<_Alloc>    {
+  typedef allocator_traits<_Alloc> _Base_type;
+  template<typename _Tp>       struct rebind       {   typedef typename _Base_type::template rebind_alloc<_Tp> other;   };
+};
+
+template<typename _Tp>     class allocator {
+  typedef _Tp value_type;
+  template<typename _Tp1>  struct rebind  {   typedef allocator<_Tp1> other;   };
+};
+
+template<typename _CharT, typename _Alloc>
+class basic_string {
+  typedef typename __alloc_traits<_Alloc>::template rebind<_CharT>::other _Char_alloc_type;
+};
+
+template<size_t _Nw>  struct _Base_bitset {
+  static void foo (basic_string<char, allocator<char> >) {}
+};