[libc] Add VISIT enum for search.h

[c8ef]

This patch introduces the VISIT enum for tree search. Existing tests ensure the correct generation of headers.

[llvmbot]

@llvm/pr-subscribers-libc

Author: Connector Switch (c8ef)

Changes

This patch introduces the VISIT enum for tree search. Existing tests ensure the correct generation of headers.

---

Full diff: https://github.com/llvm/llvm-project/pull/132746.diff

4 Files Affected:

• (modified) libc/include/CMakeLists.txt (+1)
• (modified) libc/include/llvm-libc-types/CMakeLists.txt (+1)
• (added) libc/include/llvm-libc-types/VISIT.h (+14)
• (modified) libc/include/search.yaml (+1)

diff --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
index 409737762ac41..d1e116ac547d7 100644
--- a/libc/include/CMakeLists.txt
+++ b/libc/include/CMakeLists.txt
@@ -245,6 +245,7 @@ add_header_macro(
     .llvm-libc-types.ENTRY
     .llvm-libc-types.struct_hsearch_data
     .llvm-libc-types.size_t
+    .llvm-libc-types.VISIT
     .llvm-libc-types.__lsearchcompare_t
 )
 
diff --git a/libc/include/llvm-libc-types/CMakeLists.txt b/libc/include/llvm-libc-types/CMakeLists.txt
index bf8bdfe89943c..66e8527701873 100644
--- a/libc/include/llvm-libc-types/CMakeLists.txt
+++ b/libc/include/llvm-libc-types/CMakeLists.txt
@@ -128,6 +128,7 @@ add_header(struct_iovec HDR struct_iovec.h DEPENDS .size_t)
 add_header(struct_msghdr HDR struct_msghdr.h DEPENDS .size_t .socklen_t .struct_iovec)
 add_header(ACTION HDR ACTION.h)
 add_header(ENTRY HDR ENTRY.h)
+add_header(VISIT HDR VISIT.h)
 add_header(struct_hsearch_data HDR struct_hsearch_data.h)
 add_header(struct_epoll_event HDR struct_epoll_event.h)
 add_header(struct_epoll_data HDR struct_epoll_data.h)
diff --git a/libc/include/llvm-libc-types/VISIT.h b/libc/include/llvm-libc-types/VISIT.h
new file mode 100644
index 0000000000000..0a7ff6e50d469
--- /dev/null
+++ b/libc/include/llvm-libc-types/VISIT.h
@@ -0,0 +1,14 @@
+//===-- Definition of VISIT type ------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_TYPES_VISIT_H
+#define LLVM_LIBC_TYPES_VISIT_H
+
+typedef enum { preorder, postorder, endorder, leaf } VISIT;
+
+#endif // LLVM_LIBC_TYPES_VISIT_H
diff --git a/libc/include/search.yaml b/libc/include/search.yaml
index f6f5d6cb062e5..e2e711cc93f4d 100644
--- a/libc/include/search.yaml
+++ b/libc/include/search.yaml
@@ -5,6 +5,7 @@ types:
   - type_name: struct_hsearch_data
   - type_name: ENTRY
   - type_name: ACTION
+  - type_name: VISIT
   - type_name: __lsearchcompare_t
 enums: []
 objects: []

[c8ef]

Thanks for the review!

The only thing left for search.h is the tree-search related functions. I’d like to work on that, but first, I have a few questions about the basic design choices, specifically the data structure. As far as I can tell, glibc uses a red-black tree, while musl and FreeBSD use AVL trees. There are other tree structures that could be suitable as well, like AA trees. Which one would be more appropriate here? I’m wondering if any of them would work, or if there’s a clear preference based on benchmarks or specific use cases.

[michaelrj-google]

Any of them would work. From what I can tell, the tsearch family of functions isn't widely used so it's not really performance critical.