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

[Nikolas Klauser via libcxx-commits]

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+//===----------------------------------------------------------------------===//
+//
+// 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: -Wfunction-effects -Werror=function-effects
----------------
philnik777 wrote:

```suggestion
// ADDITIONAL_COMPILE_FLAGS: -Werror=function-effects
```

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