Path: Stop claiming path::const_iterator is bidirectional

path::const_iterator claims that it's a bidirectional iterator, but it
doesn't satisfy all of the contracts for a bidirectional iterator.
For example, n3376 24.2.5 p6 says "If a and b are both dereferenceable,
then a == b if and only if *a and *b are bound to the same object",
but this doesn't work with how we stash and recreate Components.

This means that our use of reverse_iterator on this type is invalid
and leads to many of the valgrind errors we're hitting, as explained
by Tilmann Scheller here:

    http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20140728/228654.html

Instead, we admit that path::const_iterator is only an input_iterator,
and implement a second input_iterator for path::reverse_iterator (by
changing const_iterator::operator-- to reverse_iterator::operator++).
All of the uses of this just traverse once over the path in one
direction or the other anyway.

llvm-svn: 214737

1 files changed, 3 insertions, 3 deletions

diff --git a/llvm/unittests/Support/Path.cpp b/llvm/unittests/Support/Path.cpp
index db85347..bb1428f 100644
--- a/llvm/unittests/Support/Path.cpp
+++ b/llvm/unittests/Support/Path.cpp
@@ -141,7 +141,7 @@ TEST(Support, Path) {
     StringRef filename(temp_store.begin(), temp_store.size()), stem, ext;
     stem = path::stem(filename);
     ext  = path::extension(filename);
-    EXPECT_EQ(*(--sys::path::end(filename)), (stem + ext).str());
+    EXPECT_EQ(*sys::path::rbegin(filename), (stem + ext).str());
 
     path::native(*i, temp_store);
   }
@@ -227,7 +227,7 @@ TEST(Support, AbsolutePathIteratorEnd) {
 #endif
 
   for (StringRef Path : Paths) {
-    StringRef LastComponent = *--path::end(Path);
+    StringRef LastComponent = *path::rbegin(Path);
     EXPECT_EQ(".", LastComponent);
   }
 
@@ -239,7 +239,7 @@ TEST(Support, AbsolutePathIteratorEnd) {
 #endif
 
   for (StringRef Path : RootPaths) {
-    StringRef LastComponent = *--path::end(Path);
+    StringRef LastComponent = *path::rbegin(Path);
     EXPECT_EQ(1u, LastComponent.size());
     EXPECT_TRUE(path::is_separator(LastComponent[0]));
   }