Add __libcpp_version file and __libcpp_library_version function.

This patch does two seperate things. First it adds a file called
"__libcpp_version" which only contains the current libc++ version
(currently 4000). This file is not intended for use as a header. This file
is used by Clang in order to easily determine the installed libc++ version.
This allows Clang to enable/disable certain language features only when the
library supports them.

The second change is the addition of _LIBCPP_LIBRARY_VERSION macro, which
returns the version of the installed dylib since it may be different than
the headers.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@285382 91177308-0d34-0410-b5e6-96231b3b80d8

include/__config

@@ -908,6 +908,13 @@ extern "C" void __sanitizer_annotate_contiguous_container(
 #define _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
 #endif
 
+_LIBCPP_BEGIN_NAMESPACE_STD
+_LIBCPP_FUNC_VIS _LIBCPP_WEAK int __libcpp_library_version();
+_LIBCPP_END_NAMESPACE_STD
+
+#define _LIBCPP_LIBRARY_VERSION \
+ (_VSTD::__libcpp_library_version ? _VSTD::__libcpp_library_version() : -1)
+
 #endif // __cplusplus
 
 #endif // _LIBCPP_CONFIG

include/__libcpp_version

@@ -0,0 +1 @@
+4000

lib/abi/CHANGELOG.TXT

@@ -16,6 +16,11 @@ New entries should be added directly below the "Version" header.
 Version 4.0
 -----------
 
+* rTBD - Add __libcpp_library_version
+
+  all platforms
+  -------------
+  Symbol added: _ZNSt3__124__libcpp_library_versionEv
 
 * r285101 - Add -fvisibility-inlines-hidden when building libc++.
 

lib/abi/x86_64-linux-gnu.abilist

@@ -1141,6 +1141,7 @@
 {'type': 'FUNC', 'name': '_ZNSt3__121recursive_timed_mutexD1Ev'}
 {'type': 'FUNC', 'name': '_ZNSt3__121recursive_timed_mutexD2Ev'}
 {'type': 'FUNC', 'name': '_ZNSt3__121undeclare_no_pointersEPcm'}
+{'type': 'FUNC', 'name': '_ZNSt3__124__libcpp_library_versionEv'}
 {'type': 'FUNC', 'name': '_ZNSt3__125__num_get_signed_integralIlEET_PKcS3_Rji'}
 {'type': 'FUNC', 'name': '_ZNSt3__125__num_get_signed_integralIxEET_PKcS3_Rji'}
 {'type': 'FUNC', 'name': '_ZNSt3__125notify_all_at_thread_exitERNS_18condition_variableENS_11unique_lockINS_5mutexEEE'}

src/libcpp_version.cpp

@@ -0,0 +1,14 @@
+#include "__config"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// Test that _LIBCPP_VERSION and __libcpp_version are in sync.
+// The __libcpp_version file stores only a number representing the libc++
+// version so it can be easily parsed by clang.
+static_assert(_LIBCPP_VERSION ==
+#include "__libcpp_version"
+    , "version file does not match");
+
+int __libcpp_library_version() { return _LIBCPP_VERSION; }
+
+_LIBCPP_END_NAMESPACE_STD

test/libcxx/version.pass.cpp

@@ -0,0 +1,29 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// Test the _LIBCPP_VERSION and _LIBCPP_LIBRARY_VERSION macros
+
+#include <__config>
+
+#ifndef _LIBCPP_VERSION
+#error _LIBCPP_VERSION must be defined
+#endif
+
+#ifndef _LIBCPP_LIBRARY_VERSION
+#error _LIBCPP_LIBRARY_VERSION must be defined
+#endif
+
+#include <cassert>
+
+int main() {
+  assert(_LIBCPP_VERSION == _LIBCPP_LIBRARY_VERSION);
+  assert(std::__libcpp_library_version);
+  assert(_LIBCPP_LIBRARY_VERSION == std::__libcpp_library_version());
+}