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Path: Stop claiming path::const_iterator is bidirectional

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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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214737 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Justin Bogner
2014-08-04 17:36:41 +00:00
parent 93bbddf1f2
commit 981eb59138
3 changed files with 60 additions and 35 deletions
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6
unittests/Support/Path.cpp
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@@ -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]));
}