Implement filesystem NB comments, relative paths, and related issues.

This is a fairly large patch that implements all of the filesystem NB comments
and the relative paths changes (ex. adding weakly_canonical). These issues
and papers are all interrelated so their implementation couldn't be split up
nicely.

This patch upgrades <experimental/filesystem> to match the C++17 spec and not
the published experimental TS spec. Some of the changes in this patch are both
API and ABI breaking, however libc++ makes no guarantee about stability for
experimental implementations.

The major changes in this patch are:

* Implement NB comments for filesystem (P0492R2), including:
  * Implement `perm_options` enum as part of NB comments, and update the
    `permissions` function to match.
  * Implement changes to `remove_filename` and `replace_filename`
  * Implement changes to `path::stem()` and `path::extension()` which support
    splitting examples like `.profile`.
  * Change path iteration to return an empty path instead of '.' for trailing
    separators.
  * Change `operator/=` to handle absolute paths on the RHS.
  * Change `absolute` to no longer accept a current path argument.

* Implement relative paths according to NB comments (P0219r1)

* Combine `path.cpp` and `operations.cpp` since some path functions require
  access to the operations internals, and some fs operations require access
  to the path parser.

llvm-svn: 329028

1 files changed, 48 insertions, 0 deletions

diff --git a/libcxx/test/std/experimental/filesystem/fs.enum/enum.perm_options.pass.cpp b/libcxx/test/std/experimental/filesystem/fs.enum/enum.perm_options.pass.cpp
new file mode 100644
index 00000000000..c1066b63ba3
--- /dev/null
+++ b/libcxx/test/std/experimental/filesystem/fs.enum/enum.perm_options.pass.cpp
@@ -0,0 +1,48 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <experimental/filesystem>
+
+// enum class perm_options;
+
+#include "filesystem_include.hpp"
+#include <type_traits>
+#include <cassert>
+#include <sys/stat.h>
+
+#include "test_macros.h"
+#include "check_bitmask_types.hpp"
+
+
+constexpr fs::perm_options ME(int val) {
+  return static_cast<fs::perm_options>(val);
+}
+
+int main() {
+  typedef fs::perm_options E;
+  static_assert(std::is_enum<E>::value, "");
+
+  // Check that E is a scoped enum by checking for conversions.
+  typedef std::underlying_type<E>::type UT;
+  static_assert(!std::is_convertible<E, UT>::value, "");
+
+  static_assert(std::is_same<UT, unsigned char >::value, ""); // Implementation detail
+
+  typedef check_bitmask_type<E, E::replace, E::nofollow> BitmaskTester;
+  assert(BitmaskTester::check());
+
+  static_assert(
+        E::replace  == ME(1) &&
+        E::add      == ME(2) &&
+        E::remove   == ME(4) &&
+        E::nofollow == ME(8),
+        "Expected enumeration values do not match");
+}