Debugging: Report the CPU we are running on under Darwin

This can be helpful to understand complex post-mortem failures.

PiperOrigin-RevId: 715435340
Change-Id: I7e5f6abcbba043055c1b33fbc09701fa8a56984c

Author: majnemer

absl/base/config.h

@@ -405,6 +405,23 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 #define ABSL_HAVE_SCHED_GETCPU 1
 #endif
 
+// ABSL_HAVE_PTHREAD_CPU_NUMBER_NP
+//
+// Checks whether pthread_cpu_number_np is available.
+#ifdef ABSL_HAVE_PTHREAD_CPU_NUMBER_NP
+#error ABSL_HAVE_PTHREAD_CPU_NUMBER_NP cannot be directly set
+#elif defined(__APPLE__) && defined(__has_include) &&              \
+    ((defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) &&    \
+      __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ >= 110000) ||  \
+     (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) &&   \
+      __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ >= 140200) || \
+     (defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__) &&    \
+      __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ >= 70100) ||   \
+     (defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__) &&       \
+      __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ >= 140200))
+#define ABSL_HAVE_PTHREAD_CPU_NUMBER_NP 1
+#endif
+
 // ABSL_HAVE_SCHED_YIELD
 //
 // Checks whether the platform implements sched_yield(2) as defined in

absl/debugging/failure_signal_handler.cc

@@ -21,6 +21,7 @@
 #ifdef _WIN32
 #include <windows.h>
 #else
+#include <pthread.h>
 #include <sched.h>
 #include <unistd.h>
 #endif
@@ -330,6 +331,20 @@ static void ImmediateAbortSignalHandler(int) { RaiseToDefaultHandler(SIGABRT); }
 using GetTidType = decltype(absl::base_internal::GetTID());
 ABSL_CONST_INIT static std::atomic<GetTidType> failed_tid(0);
 
+static int GetCpuNumber() {
+#ifdef ABSL_HAVE_SCHED_GETCPU
+  return sched_getcpu();
+#elif defined(ABSL_HAVE_PTHREAD_CPU_NUMBER_NP)
+  size_t cpu_num;
+  if (pthread_cpu_number_np(&cpu_num) == 0) {
+    return static_cast<int>(cpu_num);
+  }
+  return -1;
+#else
+  return -1;
+#endif
+}
+
 #ifndef ABSL_HAVE_SIGACTION
 static void AbslFailureSignalHandler(int signo) {
   void* ucontext = nullptr;
@@ -360,10 +375,7 @@ static void AbslFailureSignalHandler(int signo, siginfo_t*, void* ucontext) {
   // Increase the chance that the CPU we report was the same CPU on which the
   // signal was received by doing this as early as possible, i.e. after
   // verifying that this is not a recursive signal handler invocation.
-  int my_cpu = -1;
-#ifdef ABSL_HAVE_SCHED_GETCPU
-  my_cpu = sched_getcpu();
-#endif
+  int my_cpu = GetCpuNumber();
 
 #ifdef ABSL_HAVE_ALARM
   // Set an alarm to abort the program in case this code hangs or deadlocks.