Get rid of global constructor in llvm/lib/Support/Signals.cpp in C++20 mode

[Godin]

Summary

Without this patch when using CMAKE_CXX_STANDARD=20 and Clang 13
build fails with

llvm/lib/Support/Signals.cpp:86:26: error: declaration requires a global constructor [-Werror,-Wglobal-constructors]

[mehdi_amini]

LGTM, but do you know what explains this behavior in C++20?

llvm/lib/Support/Signals.cpp

86

Do you

[Godin]

Superseded by https://reviews.llvm.org/D122067

llvm/lib/Support/Signals.cpp

 //===- Signals.cpp - Signal Handling support --------------------*- 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
 //
 //===----------------------------------------------------------------------===//
 //

 // callbacks, an array is therefore sufficient.
 struct CallbackAndCookie {
   sys::SignalHandlerCallback Callback;
   void *Cookie;
   enum class Status { Empty, Initializing, Initialized, Executing };
   std::atomic<Status> Flag;
 };
 static constexpr size_t MaxSignalHandlerCallbacks = 8;
-static CallbackAndCookie CallBacksToRun[MaxSignalHandlerCallbacks];
+static CallbackAndCookie CallBacksToRun[MaxSignalHandlerCallbacks]{};
 
 // Signal-safe.
 void sys::RunSignalHandlers() {
   for (CallbackAndCookie &RunMe : CallBacksToRun) {
     auto Expected = CallbackAndCookie::Status::Initialized;
     auto Desired = CallbackAndCookie::Status::Executing;
     if (!RunMe.Flag.compare_exchange_strong(Expected, Desired))
       continue;