[libSupport] make CallBacksToRun static local

[tal.kedar]

Summary

In order to allow compiling with -Werror=global-constructors with c++20 and above.

Discussion: https://discourse.llvm.org/t/llvm-lib-support-signals-cpp-fails-to-compile-due-to-werror-global-constructors/61070

[tal.kedar]

Fix formatting.

[tal.kedar]

Fix formatting, take II

[mehdi_amini]

LG, thanks!

[tal.kedar]

Next step is to add a comment here that I cannot commit myself?

[mehdi_amini]

In D122067#3394356, @tal.kedar wrote:

Next step is to add a comment here that I cannot commit myself?

What should be name/email to use for the commit authorship here?

[tal.kedar]

In D122067#3394357, @mehdi_amini wrote:

What should be name/email to use for the commit authorship here?

Tal Kedar
[e-mail]

Thanks!

llvm/lib/Support/Signals.cpp

 #include "llvm/Support/Format.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Program.h"
 #include "llvm/Support/StringSaver.h"
 #include "llvm/Support/raw_ostream.h"
+#include <array>
 #include <vector>
 
 //===----------------------------------------------------------------------===//
 //=== WARNING: Implementation here must contain only TRULY operating system
 //===          independent code.
 //===----------------------------------------------------------------------===//
 
 using namespace llvm;

 // could be running as we add new callbacks. We don't add unbounded numbers of
 // 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];
+
+// A global array of CallbackAndCookie may not compile with
+// -Werror=global-constructors in c++20 and above
+static std::array<CallbackAndCookie, MaxSignalHandlerCallbacks> &
+CallBacksToRun() {
+  static std::array<CallbackAndCookie, MaxSignalHandlerCallbacks> callbacks;
+  return callbacks;
+}
 
 // Signal-safe.
 void sys::RunSignalHandlers() {
-  for (CallbackAndCookie &RunMe : CallBacksToRun) {
+  for (CallbackAndCookie &RunMe : CallBacksToRun()) {
     auto Expected = CallbackAndCookie::Status::Initialized;
     auto Desired = CallbackAndCookie::Status::Executing;
     if (!RunMe.Flag.compare_exchange_strong(Expected, Desired))
       continue;
     (*RunMe.Callback)(RunMe.Cookie);
     RunMe.Callback = nullptr;
     RunMe.Cookie = nullptr;
     RunMe.Flag.store(CallbackAndCookie::Status::Empty);
   }
 }
 
 // Signal-safe.
 static void insertSignalHandler(sys::SignalHandlerCallback FnPtr,
                                 void *Cookie) {
-  for (CallbackAndCookie &SetMe : CallBacksToRun) {
+  for (CallbackAndCookie &SetMe : CallBacksToRun()) {
     auto Expected = CallbackAndCookie::Status::Empty;
     auto Desired = CallbackAndCookie::Status::Initializing;
     if (!SetMe.Flag.compare_exchange_strong(Expected, Desired))
       continue;
     SetMe.Callback = FnPtr;
     SetMe.Cookie = Cookie;
     SetMe.Flag.store(CallbackAndCookie::Status::Initialized);
     return;