[libc++] Revert removal of <movable_box.h> to fix lldb test failure

[winner245]

The removal of <__ranges/movable_box.h> from <__algorithm/for_each.h> (#134960) caused lldb test failures (#137046) due to an implicit dependency in clang's AST processing. After discussion with @dmpots, we confirmed that re-adding this header represents the simplest fix for now.

This is a temporary fix for #137046. A long-term resolution may require deeper investigation into lldb and clang behavior.

[llvmbot]

@llvm/pr-subscribers-lldb

@llvm/pr-subscribers-libcxx

Author: Peng Liu (winner245)

Changes

The removal of <__ranges/movable_box.h> from <__algorithm/for_each.h> (#134960) caused lldb test failures (#137046) due to an implicit dependency in clang's AST processing. After discussion with @dmpots, we confirmed that re-adding this header represents the simplest fix for now.

Note: This is a temporary solution. A long-term resolution may require deeper investigation into lldb and clang behavior.

---

Full diff: https://github.com/llvm/llvm-project/pull/140960.diff

1 Files Affected:

• (modified) libcxx/include/__algorithm/for_each.h (+1)

diff --git a/libcxx/include/__algorithm/for_each.h b/libcxx/include/__algorithm/for_each.h
index b6c2c7c056edd..9bbccbdd0a5a2 100644
--- a/libcxx/include/__algorithm/for_each.h
+++ b/libcxx/include/__algorithm/for_each.h
@@ -13,6 +13,7 @@
 #include <__algorithm/for_each_segment.h>
 #include <__config>
 #include <__iterator/segmented_iterator.h>
+#include <__ranges/movable_box.h> // Re-included as a temporary fix for lldb test failure (https://github.com/llvm/llvm-project/issues/137046)
 #include <__type_traits/enable_if.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)

[ldionne]

As said in #137046 (comment), I think we might as well mark the failing test as unsupported in LLDB. And then we remove the UNSUPPORTED annotation once the bug is fixed.

So I'm not sure we need to actually land this change.

[winner245]

@ldionne I agree with your plan. This is not a bug in libc++. It is better to mark the failing test as unsupported in LLDB as a temporary fix, and then remove the UNSUPPORTED annotation once a long-term fix is available. That said, I will close this PR.

[Michael137]

This is not a bug in libc++. It is better to mark the failing test as unsupported in LLDB

FWIW, I don't think this is the correct stance to take in general with these types of issues. If something breaks in a different subproject, reverting/waiting for the subproject to figure out a fix is what we typically would/should do in LLVM. But since this has been sitting for a while now and this part of LLDB is rather experimental, I agree that's what we should do in this case