[libc][annex_k] Add libc_constraint_handler.

[bassiounix]

RFC https://discourse.llvm.org/t/rfc-bounds-checking-interfaces-for-llvm-libc/87685

Add internal libc_constraint_handler required by Annex K interface in LLVM libc.

[bassiounix]

Warning

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• [libc][stdlib][annex_k] Add set_constraint_handler_s. #163320
• [libc][annex_k] Add libc_constraint_handler macros. #163316
• [libc][annex_k] Add libc_constraint_handler. #163315 👈 (View in Graphite)
• [libc][stdlib][annex_k] Add ignore_handler_s. #163313
• [libc][stdlib][annex_k] Add abort_handler_s. #163309
• [libc][annex_k] Add constraint_handler_t. #163239 : 2 other dependent PRs (#163869 , #164089 )
• [libc][annex_k] Add rsize_t. #163238
• [libc][annex_k] Add errno_t. #163094
• [libc][annex_k] Add Annex K support macros. #163100
• main

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[llvmbot]

@llvm/pr-subscribers-libc

Author: Muhammad Bassiouni (bassiounix)

Changes

RFC https://discourse.llvm.org/t/rfc-bounds-checking-interfaces-for-llvm-libc/87685

Add internal libc_constraint_handler required by Annex K interface in LLVM libc.

---

Full diff: https://github.com/llvm/llvm-project/pull/163315.diff

3 Files Affected:

• (modified) libc/src/__support/annex_k/CMakeLists.txt (+9)
• (added) libc/src/__support/annex_k/libc_constraint_handler.h (+26)
• (added) libc/src/__support/annex_k/macros.h (+44)

diff --git a/libc/src/__support/annex_k/CMakeLists.txt b/libc/src/__support/annex_k/CMakeLists.txt
index 78f5b3cddebd7..8eb65f2469b4f 100644
--- a/libc/src/__support/annex_k/CMakeLists.txt
+++ b/libc/src/__support/annex_k/CMakeLists.txt
@@ -10,3 +10,12 @@ add_header_library(
     libc.src.__support.OSUtil.osutil
     libc.src.stdlib.abort
 )
+
+add_header_library(
+  libc_constraint_handler
+  HDRS
+    libc_constraint_handler.h
+  DEPENDS
+    .abort_handler_s
+    libc.hdr.types.constraint_handler_t
+)
diff --git a/libc/src/__support/annex_k/libc_constraint_handler.h b/libc/src/__support/annex_k/libc_constraint_handler.h
new file mode 100644
index 0000000000000..db01c8dd940a0
--- /dev/null
+++ b/libc/src/__support/annex_k/libc_constraint_handler.h
@@ -0,0 +1,26 @@
+//===-- Static header for libc_constraint_handler ---------------*- C++ -*-===//
+//
+// 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_SRC___SUPPORT_ANNEX_K_LIBC_CONSTRAINT_HANDLER_H
+#define LLVM_LIBC_SRC___SUPPORT_ANNEX_K_LIBC_CONSTRAINT_HANDLER_H
+
+#include "abort_handler_s.h"
+#include "hdr/types/constraint_handler_t.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace annex_k {
+
+LIBC_INLINE static constraint_handler_t libc_constraint_handler =
+    &abort_handler_s;
+
+} // namespace annex_k
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif  // LLVM_LIBC_SRC___SUPPORT_ANNEX_K_LIBC_CONSTRAINT_HANDLER_H
diff --git a/libc/src/__support/annex_k/macros.h b/libc/src/__support/annex_k/macros.h
new file mode 100644
index 0000000000000..835c161dd0d30
--- /dev/null
+++ b/libc/src/__support/annex_k/macros.h
@@ -0,0 +1,44 @@
+//===-- Helper macros header for constraint violations ----------*- C++ -*-===//
+//
+// 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_SRC___SUPPORT_ANNEX_K_MACROS_H
+#define LLVM_LIBC_SRC___SUPPORT_ANNEX_K_MACROS_H
+
+#include "libc_constraint_handler.h"
+#include "src/__support/libc_errno.h"
+
+#define _CONSTRAINT_VIOLATION(msg, error_code, ret_code)                       \
+  {                                                                            \
+    libc_errno = error_code;                                                   \
+    libc_constraint_handler(msg, nullptr, error_code);                         \
+    return ret_code;                                                           \
+  }
+
+#define _CONSTRAINT_VIOLATION_IF(expr, error_code, return_code)                \
+  {                                                                            \
+    auto expr_val = expr;                                                      \
+    if (expr_val) {                                                            \
+      libc_errno = error_code;                                                 \
+      libc_constraint_handler(nullptr, nullptr, error_code);                   \
+      return return_code;                                                      \
+    }                                                                          \
+  }
+
+#define _CONSTRAINT_VIOLATION_CLEANUP_IF(expr, cleanup, error_code,            \
+                                         return_code)                          \
+  {                                                                            \
+    auto expr_val = expr;                                                      \
+    if (expr_val) {                                                            \
+      cleanup;                                                                 \
+      libc_errno = error_code;                                                 \
+      libc_constraint_handler(nullptr, nullptr, error_code);                   \
+      return return_code;                                                      \
+    }                                                                          \
+  }
+
+#endif // LLVM_LIBC_SRC___SUPPORT_ANNEX_K_MACROS_H

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