Disable the profiler when a debugger is attached

runtime/vm/thread_interrupter_macos.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_MACOS)
 
 #include <errno.h>  // NOLINT
+#include <assert.h>      // NOLINT
+#include <stdbool.h>     // NOLINT
+#include <sys/types.h>   // NOLINT
+#include <unistd.h>      // NOLINT
+#include <sys/sysctl.h>  // NOLINT
 
 #include "vm/flags.h"
 #include "vm/os.h"
 #include "vm/profiler.h"
 #include "vm/signal_handler.h"
 #include "vm/thread_interrupter.h"
 
 namespace dart {
 
 #ifndef PRODUCT
 
 DECLARE_FLAG(bool, thread_interrupter);
 DECLARE_FLAG(bool, trace_thread_interrupter);
 
+// Returns true if the current process is being debugged (either
+// running under the debugger or has a debugger attached post facto).
+// Code from https://developer.apple.com/library/content/qa/qa1361/_index.html
+bool ThreadInterrupter::IsDebuggerAttached() {
+  struct kinfo_proc info;
+  // Initialize the flags so that, if sysctl fails for some bizarre
+  // reason, we get a predictable result.
+  info.kp_proc.p_flag = 0;
+  // Initialize mib, which tells sysctl the info we want, in this case
+  // we're looking for information about a specific process ID.
+  int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PID, getpid()};
+  size_t size = sizeof(info);
+
+  // Call sysctl.
+  size = sizeof(info);
+  int junk = sysctl(mib, sizeof(mib) / sizeof(*mib), &info, &size, NULL, 0);
+  ASSERT(junk == 0);
+  // We're being debugged if the P_TRACED flag is set.
+  return ((info.kp_proc.p_flag & P_TRACED) != 0);
+}
+
 class ThreadInterrupterMacOS : public AllStatic {
  public:
   static void ThreadInterruptSignalHandler(int signal,
                                            siginfo_t* info,
                                            void* context_) {
     if (signal != SIGPROF) {
       return;
     }
     Thread* thread = Thread::Current();
     if (thread == NULL) {
       return;
     }
     // Extract thread state.
     ucontext_t* context = reinterpret_cast<ucontext_t*>(context_);
     mcontext_t mcontext = context->uc_mcontext;
     InterruptedThreadState its;
     its.pc = SignalHandler::GetProgramCounter(mcontext);
     its.fp = SignalHandler::GetFramePointer(mcontext);
     its.csp = SignalHandler::GetCStackPointer(mcontext);
     its.dsp = SignalHandler::GetDartStackPointer(mcontext);
     its.lr = SignalHandler::GetLinkRegister(mcontext);
     Profiler::SampleThread(thread, its);
   }
 };
 
 
 void ThreadInterrupter::InterruptThread(OSThread* thread) {
   if (FLAG_trace_thread_interrupter) {
-    OS::Print("ThreadInterrupter interrupting %p\n", thread->id());
+    OS::PrintErr("ThreadInterrupter interrupting %p\n", thread->id());
   }
   int result = pthread_kill(thread->id(), SIGPROF);
   ASSERT((result == 0) || (result == ESRCH));
 }
 
 
 void ThreadInterrupter::InstallSignalHandler() {
   SignalHandler::Install<
       ThreadInterrupterMacOS::ThreadInterruptSignalHandler>();
 }
 
 
 void ThreadInterrupter::RemoveSignalHandler() {
   SignalHandler::Remove();
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)