[libcxx-commits] [libcxx] [libc++] Handle Clang function effect analysis in hardening assertions (PR #177447)

[Nikolas Klauser via libcxx-commits]

================
@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// GCC doesn't support -Wfunction-effect-analysis and the associated attributes
+// UNSUPPORTED: gcc
+
+// The observe semantic requires experimental support for now.
+// XFAIL: libcpp-has-no-experimental-hardening-observe-semantic
+
+// Make sure that libc++ assertions are compatible with the function effect analysis
+// extension in Clang. The function effect analysis extension allows marking functions
+// with attributes like [[nonblocking]], and Clang will issue a diagnostic if such a
+// function calls another function that doesn't satisfy the requirements of the attribute.
+//
+// However, libc++'s assertion functions are called in a context where a precondition
+// has been violated. Hence, it is acceptable not to satisfy these function effect
+// attributes once the assertion is known to fail.
+//
+// This test ensures that we properly disable function effect analysis diagnostics
+// in libc++'s assertion macros, otherwise it becomes impossible to call a function
+// with hardened preconditions from e.g. a [[nonblocking]] function.
+
+// ADDITIONAL_COMPILE_FLAGS: -Werror=function-effects
+
+// RUN: %{verify}
+// RUN: %{verify} -D_LIBCPP_ASSERTION_SEMANTIC=_LIBCPP_ASSERTION_SEMANTIC_IGNORE
+// RUN: %{verify} -D_LIBCPP_ASSERTION_SEMANTIC=_LIBCPP_ASSERTION_SEMANTIC_OBSERVE
+// RUN: %{verify} -D_LIBCPP_ASSERTION_SEMANTIC=_LIBCPP_ASSERTION_SEMANTIC_QUICK_ENFORCE
+// RUN: %{verify} -D_LIBCPP_ASSERTION_SEMANTIC=_LIBCPP_ASSERTION_SEMANTIC_ENFORCE
+
+#include <cstddef>
+#include <span>
+
+// Using _LIBCPP_ASSERT directly
+void f(bool condition) noexcept [[clang::nonblocking]] {
+  _LIBCPP_ASSERT(condition, "message"); // nothing
+}
+void g(bool condition) noexcept [[clang::nonallocating]] {
+  _LIBCPP_ASSERT(condition, "message"); // nothing
+}
+
+// Sanity check with an actual std::span
+void f(std::span<int> span, std::size_t index) noexcept [[clang::nonblocking]] {
+  (void)span[index]; // nothing
+}
+void g(std::span<int> span, std::size_t index) noexcept [[clang::nonallocating]] {
+  (void)span[index]; // nothing
+}
+
+// Test the test: ensure that a diagnostic would be emitted normally
+void __potentially_blocking();
----------------
philnik777 wrote:

Why the reserved name?

https://github.com/llvm/llvm-project/pull/177447