[PATCH] Make __wrap_iter work with gcc

[Nico Weber]

Hi danalbert,

The following snippet doesn't build when using gcc and libc++:

```
#include <string>
void f(const std::string& s) { s.begin(); }
#include <vector>
void AppendTo(const std::vector<char>& v) { v.begin(); }
```

The problem is that __wrap_iter has a private constructor. It lists vector<> and basic_string<> as friends, but gcc seems to ignore this for vector<> for some reason. Declaring vector before the friend declaration in __wrap_iter is enough to work around this problem, so do that. With this patch, I'm able to build chromium/android with libc++. Without it, two translation units fail to build.

As far as I can tell, this is due to a gcc bug, which I filed as https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64816.

Fixes PR22355.

http://reviews.llvm.org/D7201

Files:
  include/iterator
  test/std/iterators/iterators.general/gcc_workaround.pass.cpp

Index: include/iterator
===================================================================
--- include/iterator
+++ include/iterator
@@ -1112,6 +1112,8 @@
 >::type
 __unwrap_iter(__wrap_iter<_Tp*>);
 
+template <class _Tp, class _Alloc> class vector;
+
 template <class _Iter>
 class __wrap_iter
 {
Index: test/std/iterators/iterators.general/gcc_workaround.pass.cpp
===================================================================
--- test/std/iterators/iterators.general/gcc_workaround.pass.cpp
+++ test/std/iterators/iterators.general/gcc_workaround.pass.cpp
@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// Tests workaround for  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64816.
+
+#include <string>
+
+void f(const std::string &s) { s.begin(); }
+
+#include <vector>
+
+void AppendTo(const std::vector<char> &v) { v.begin(); }
+
+int main() {}

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