[Support] Remove LLVM_ATTRIBUTE_NORETURN

[gAlfonso-bit]

Summary

Code should use C++11 [[noreturn]] or C11 _Noreturn instead.

[gAlfonso-bit]

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[mclow.lists]

I would like to see you undo all the formatting changes.
They are not germane for this patch, and (IMHO) reduce the readability of the code.

[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[mclow.lists]

In D106899#2908395, @gAlfonso-bit wrote:

Done!

Thank you. That's *much* easier to review.

[mclow.lists]

I am not an approver for LLVM, but this LGTM.

[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[MaskRay]

[[noreturn]] is C++11.
In Oct 2016, the minimum compiler requirement was raised to GCC 4.8/MSVC 2015.
We can use [[noreturn]] since then.

I migrated lld/. I will watch the build bots and migrate llvm/

[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[MaskRay]

I migrated all llvm/ files. You need to remove them from the patch.

It is a good idea to drop the macro definition in llvm/include/llvm/Support/Compiler.h separately.

It makes it easy to bring back the definition if some important downstream users want extended time for migration.
(Note: the policy is that downstream is on their own. Our thinking of this is kindness, not an obligation of llvm-project.)
For example, swift is using LLVM_ATTRIBUTE_NORETURN.
(I researched a bit: LLVM_ATTRIBUTE_NORETURN is not common in downstream projects.)

[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[MaskRay]

Drop llvm/include/llvm/Support/Compiler.h change.

[gAlfonso-bit]

Removed Compiler.h changes

[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[MaskRay]

In D106899#2913925, @gAlfonso-bit wrote:

Still not passing (what is going on?)

If you click a harbomaster URI, sometimes the builds are good

x64 debian passed
x64 windows passed

and sometimes there may be failures apparently unrelated to your patch.
Some discretion is needed.

I ended up making the refactoring by myself. Your change included some whole-file clang-format formatting which wasn't suitable.
I usually run git diff -U0 --no-color 'HEAD^' | clang/tools/clang-format/clang-format-diff.py -i -p1 to only format related lines.

[gAlfonso-bit]

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clang-tools-extra/pp-trace/PPTrace.cpp

     cl::desc("Output trace to the given file name or '-' for stdout."),
     cl::cat(Cat));
 
-LLVM_ATTRIBUTE_NORETURN static void error(Twine Message) {
+[[noreturn]] static void error(Twine Message) {
   WithColor::error() << Message << '\n';
   exit(1);
 }

clang/utils/TableGen/ClangDiagnosticsEmitter.cpp

     return It->second.Root;
   }
 
-  LLVM_ATTRIBUTE_NORETURN void PrintFatalError(llvm::Twine const &Msg) const {
+  [[noreturn]] void PrintFatalError(llvm::Twine const &Msg) const {
     assert(EvaluatingRecord && "not evaluating a record?");
     llvm::PrintFatalError(EvaluatingRecord->getLoc(), Msg);
   }

flang/include/flang/Optimizer/Support/FatalError.h

 
 /// Fatal error reporting helper. Report a fatal error with a source location
 /// and immediately abort flang.
-LLVM_ATTRIBUTE_NORETURN inline void emitFatalError(mlir::Location loc,
-                                                   const llvm::Twine &message) {
+[[noreturn]] inline void emitFatalError(mlir::Location loc,
   mlir::emitError(loc, message);
   llvm::report_fatal_error("aborting");
 }

lldb/source/Host/posix/ProcessLauncherPosixFork.cpp

 #include <sys/wait.h>
 #include <unistd.h>
 
-#include <sstream>
 #include <csignal>
+#include <sstream>
 
 #ifdef __ANDROID__
 #include <android/api-level.h>

 #endif
 }
 
-static void LLVM_ATTRIBUTE_NORETURN ExitWithError(int error_fd,
-                                                  const char *operation) {
+[[noreturn]] static void ExitWithError(int error_fd, const char *operation) {
   int err = errno;
   llvm::raw_fd_ostream os(error_fd, true);
   os << operation << " failed: " << llvm::sys::StrError(err);

   _exit(1);
 }
 
-static void DisableASLRIfRequested(int error_fd, const ProcessLaunchInfo &info) {
+static void DisableASLRIfRequested(int error_fd,
+                                   const ProcessLaunchInfo &info) {
 #if defined(__linux__)
   if (info.GetFlags().Test(lldb::eLaunchFlagDisableASLR)) {
     const unsigned long personality_get_current = 0xffffffff;

 
 static void DupDescriptor(int error_fd, const FileSpec &file_spec, int fd,
                           int flags) {
-  int target_fd = llvm::sys::RetryAfterSignal(-1, ::open,
-      file_spec.GetCString(), flags, 0666);
+  int target_fd = llvm::sys::RetryAfterSignal(
+      -1, ::open, file_spec.GetCString(), flags, 0666);
 
   if (target_fd == -1)
     ExitWithError(error_fd, "DupDescriptor-open");

   return;
 }
 
-static void LLVM_ATTRIBUTE_NORETURN ChildFunc(int error_fd,
-                                              const ProcessLaunchInfo &info) {
+[[noreturn]] static void ChildFunc(int error_fd,
   if (info.GetFlags().Test(eLaunchFlagLaunchInSeparateProcessGroup)) {
     if (setpgid(0, 0) != 0)
       ExitWithError(error_fd, "setpgid");

lldb/source/Plugins/Process/Linux/SingleStepCheck.cpp

 #if defined(__arm64__) || defined(__aarch64__)
 namespace {
 
-void LLVM_ATTRIBUTE_NORETURN Child() {
+[[noreturn]] void Child() {
   if (ptrace(PTRACE_TRACEME, 0, nullptr, nullptr) == -1)
     _exit(1);
 

llvm/include/llvm/Support/Compiler.h

 #define LLVM_ATTRIBUTE_ALWAYS_INLINE inline
 #endif
 
-#ifdef __GNUC__
-#define LLVM_ATTRIBUTE_NORETURN __attribute__((noreturn))
-#elif defined(_MSC_VER)
-#define LLVM_ATTRIBUTE_NORETURN __declspec(noreturn)
+// C++ has [[noreturn]]. We are going to remove this eventually, but for now
+// let's keep it
+#ifdef(__cplusplus)
+#define LLVM_ATTRIBUTE_NORETURN [[noreturn]]
 #else
-#define LLVM_ATTRIBUTE_NORETURN
+#define LLVM_ATTRIBUTE_NORETURN _Noreturn
 #endif
 
 #if __has_attribute(returns_nonnull) || LLVM_GNUC_PREREQ(4, 9, 0)