Diagnose when reverse_iterator is used on path::iterator.

path::iterator isn't a strictly conforming iterator. Specifically
it stashes the current element inside the iterator. This leads to
UB when used with reverse_iterator since it requires the element
to outlive the lifetime of the iterator.

This patch adds a static_assert inside reverse_iterator to disallow
"stashing iterator types", and it tags path::iterator as such a type.

Additionally this patch removes all uses of reverse_iterator<path::iterator>
within the tests.

llvm-svn: 300164

1 files changed, 5 insertions, 7 deletions

diff --git a/libcxx/test/std/experimental/filesystem/class.path/path.member/path.decompose/path.decompose.pass.cpp b/libcxx/test/std/experimental/filesystem/class.path/path.member/path.decompose/path.decompose.pass.cpp
index 4c83481aaf2..078e006663e 100644
--- a/libcxx/test/std/experimental/filesystem/class.path/path.member/path.decompose/path.decompose.pass.cpp
+++ b/libcxx/test/std/experimental/filesystem/class.path/path.member/path.decompose/path.decompose.pass.cpp
@@ -54,12 +54,6 @@
 #include "count_new.hpp"
 #include "filesystem_test_helper.hpp"
 
-template <class It>
-std::reverse_iterator<It> mkRev(It it) {
-  return std::reverse_iterator<It>(it);
-}
-
-
 namespace fs = std::experimental::filesystem;
 struct PathDecomposeTestcase
 {
@@ -147,7 +141,11 @@ void decompPathTest()
     assert(checkCollectionsEqual(p.begin(), p.end(),
                                  TC.elements.begin(), TC.elements.end()));
     // check backwards
-    assert(checkCollectionsEqual(mkRev(p.end()), mkRev(p.begin()),
+
+    std::vector<fs::path> Parts;
+    for (auto it = p.end(); it != p.begin(); )
+      Parts.push_back(*--it);
+    assert(checkCollectionsEqual(Parts.begin(), Parts.end(),
                                  TC.elements.rbegin(), TC.elements.rend()));
   }
 }