Export of internal Abseil changes

--
1609589925459c2c0b2a17912c0d65227f709db9 by Abseil Team <absl-team@google.com>:

Clarify the "Potential Mutex deadlock" reason message.

PiperOrigin-RevId: 351367862

--
88bf28863db2c2d2d48767c3e4dfab6a48bdff79 by Abseil Team <absl-team@google.com>:

Print CPU number is fault handler.

This CL adds code to print CPU number inside the fault handler.  This is only supported on Linux.  The CPU number is also a hint only.  There is no guarantee that it is indeed the CPU on which a fault happened.

PiperOrigin-RevId: 351238373

--
66a9c8e44b5744fec1ca0d7b8db7e1d50772d9a2 by Samuel Benzaquen <sbenza@google.com>:

Add better error message for ODR violations of flags.

PiperOrigin-RevId: 351197423

--
6efd1efb341563148dd43255aaa4bf959dfd9554 by Chris Kennelly <ckennelly@google.com>:

Assume bitwise builtins are available on GCC.

These are long-standing builtins but are not consistently detected by
ABSL_HAVE_BUILTIN.

PiperOrigin-RevId: 350814036
GitOrigin-RevId: 1609589925459c2c0b2a17912c0d65227f709db9
Change-Id: Ied3fd2f135187f2c316b403fba45f3bbaea54138

11 files changed, 100 insertions, 34 deletions

diff --git a/absl/base/config.h b/absl/base/config.h
index c9a06f1d..f6ddf0c5 100644
--- a/absl/base/config.h
+++ b/absl/base/config.h
@@ -379,6 +379,15 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 #define ABSL_HAVE_PTHREAD_GETSCHEDPARAM 1
 #endif
 
+// ABSL_HAVE_SCHED_GETCPU
+//
+// Checks whether sched_getcpu is available.
+#ifdef ABSL_HAVE_SCHED_GETCPU
+#error ABSL_HAVE_SCHED_GETCPU cannot be directly set
+#elif defined(__linux__)
+#define ABSL_HAVE_SCHED_GETCPU 1
+#endif
+
 // ABSL_HAVE_SCHED_YIELD
 //
 // Checks whether the platform implements sched_yield(2) as defined in
diff --git a/absl/debugging/failure_signal_handler.cc b/absl/debugging/failure_signal_handler.cc
index 5d13bdbb..a9ed6ef9 100644
--- a/absl/debugging/failure_signal_handler.cc
+++ b/absl/debugging/failure_signal_handler.cc
@@ -21,6 +21,7 @@
 #ifdef _WIN32
 #include <windows.h>
 #else
+#include <sched.h>
 #include <unistd.h>
 #endif
 
@@ -219,17 +220,24 @@ static void WriteToStderr(const char* data) {
   absl::raw_logging_internal::SafeWriteToStderr(data, strlen(data));
 }
 
-static void WriteSignalMessage(int signo, void (*writerfn)(const char*)) {
-  char buf[64];
+static void WriteSignalMessage(int signo, int cpu,
+                               void (*writerfn)(const char*)) {
+  char buf[96];
+  char on_cpu[32] = {0};
+  if (cpu != -1) {
+    snprintf(on_cpu, sizeof(on_cpu), " on cpu %d", cpu);
+  }
   const char* const signal_string =
       debugging_internal::FailureSignalToString(signo);
   if (signal_string != nullptr && signal_string[0] != '\0') {
-    snprintf(buf, sizeof(buf), "*** %s received at time=%ld ***\n",
+    snprintf(buf, sizeof(buf), "*** %s received at time=%ld%s ***\n",
              signal_string,
-             static_cast<long>(time(nullptr)));  // NOLINT(runtime/int)
+             static_cast<long>(time(nullptr)),   // NOLINT(runtime/int)
+             on_cpu);
   } else {
-    snprintf(buf, sizeof(buf), "*** Signal %d received at time=%ld ***\n",
-             signo, static_cast<long>(time(nullptr)));  // NOLINT(runtime/int)
+    snprintf(buf, sizeof(buf), "*** Signal %d received at time=%ld%s ***\n",
+             signo, static_cast<long>(time(nullptr)),  // NOLINT(runtime/int)
+             on_cpu);
   }
   writerfn(buf);
 }
@@ -269,10 +277,10 @@ ABSL_ATTRIBUTE_NOINLINE static void WriteStackTrace(
 // Called by AbslFailureSignalHandler() to write the failure info. It is
 // called once with writerfn set to WriteToStderr() and then possibly
 // with writerfn set to the user provided function.
-static void WriteFailureInfo(int signo, void* ucontext,
+static void WriteFailureInfo(int signo, void* ucontext, int cpu,
                              void (*writerfn)(const char*)) {
   WriterFnStruct writerfn_struct{writerfn};
-  WriteSignalMessage(signo, writerfn);
+  WriteSignalMessage(signo, cpu, writerfn);
   WriteStackTrace(ucontext, fsh_options.symbolize_stacktrace, WriterFnWrapper,
                   &writerfn_struct);
 }
@@ -334,6 +342,14 @@ 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
+
 #ifdef ABSL_HAVE_ALARM
   // Set an alarm to abort the program in case this code hangs or deadlocks.
   if (fsh_options.alarm_on_failure_secs > 0) {
@@ -344,12 +360,12 @@ static void AbslFailureSignalHandler(int signo, siginfo_t*, void* ucontext) {
 #endif
 
   // First write to stderr.
-  WriteFailureInfo(signo, ucontext, WriteToStderr);
+  WriteFailureInfo(signo, ucontext, my_cpu, WriteToStderr);
 
   // Riskier code (because it is less likely to be async-signal-safe)
   // goes after this point.
   if (fsh_options.writerfn != nullptr) {
-    WriteFailureInfo(signo, ucontext, fsh_options.writerfn);
+    WriteFailureInfo(signo, ucontext, my_cpu, fsh_options.writerfn);
   }
 
   if (fsh_options.call_previous_handler) {
diff --git a/absl/debugging/failure_signal_handler_test.cc b/absl/debugging/failure_signal_handler_test.cc
index d8283b2f..6a62428b 100644
--- a/absl/debugging/failure_signal_handler_test.cc
+++ b/absl/debugging/failure_signal_handler_test.cc
@@ -122,6 +122,12 @@ TEST_P(FailureSignalHandlerDeathTest, AbslFatalSignalsWithWriterFn) {
           "*** ", absl::debugging_internal::FailureSignalToString(signo),
           " received at ")));
 
+  // On platforms where it is possible to get the current CPU, the
+  // CPU number is also logged. Check that it is present in output.
+#if defined(__linux__)
+  EXPECT_THAT(error_line, testing::HasSubstr(" on cpu "));
+#endif
+
   if (absl::debugging_internal::StackTraceWorksForTest()) {
     std::getline(error_output, error_line);
     EXPECT_THAT(error_line, StartsWith("PC: "));
diff --git a/absl/flags/flag.h b/absl/flags/flag.h
index a9cb2b79..f09580b0 100644
--- a/absl/flags/flag.h
+++ b/absl/flags/flag.h
@@ -301,13 +301,15 @@ ABSL_NAMESPACE_END
 #if ABSL_FLAGS_STRIP_NAMES
 #define ABSL_FLAG_IMPL_FLAGNAME(txt) ""
 #define ABSL_FLAG_IMPL_FILENAME() ""
-#define ABSL_FLAG_IMPL_REGISTRAR(T, flag) \
-  absl::flags_internal::FlagRegistrar<T, false>(ABSL_FLAG_IMPL_FLAG_PTR(flag))
+#define ABSL_FLAG_IMPL_REGISTRAR(T, flag)                                      \
+  absl::flags_internal::FlagRegistrar<T, false>(ABSL_FLAG_IMPL_FLAG_PTR(flag), \
+                                                nullptr)
 #else
 #define ABSL_FLAG_IMPL_FLAGNAME(txt) txt
 #define ABSL_FLAG_IMPL_FILENAME() __FILE__
-#define ABSL_FLAG_IMPL_REGISTRAR(T, flag) \
-  absl::flags_internal::FlagRegistrar<T, true>(ABSL_FLAG_IMPL_FLAG_PTR(flag))
+#define ABSL_FLAG_IMPL_REGISTRAR(T, flag)                                     \
+  absl::flags_internal::FlagRegistrar<T, true>(ABSL_FLAG_IMPL_FLAG_PTR(flag), \
+                                               __FILE__)
 #endif
 
 // ABSL_FLAG_IMPL macro definition conditional on ABSL_FLAGS_STRIP_HELP
diff --git a/absl/flags/flag_test.cc b/absl/flags/flag_test.cc
index 72507b99..6912b546 100644
--- a/absl/flags/flag_test.cc
+++ b/absl/flags/flag_test.cc
@@ -177,7 +177,7 @@ bool TestConstructionFor(const absl::Flag<T>& f1, absl::Flag<T>& f2) {
   EXPECT_EQ(absl::GetFlagReflectionHandle(f1).Help(), "literal help");
   EXPECT_EQ(absl::GetFlagReflectionHandle(f1).Filename(), "file");
 
-  flags::FlagRegistrar<T, false>(ABSL_FLAG_IMPL_FLAG_PTR(f2))
+  flags::FlagRegistrar<T, false>(ABSL_FLAG_IMPL_FLAG_PTR(f2), nullptr)
       .OnUpdate(TestCallback);
 
   EXPECT_EQ(absl::GetFlagReflectionHandle(f2).Name(), "f2");
diff --git a/absl/flags/internal/flag.h b/absl/flags/internal/flag.h
index 83548143..e6bade0a 100644
--- a/absl/flags/internal/flag.h
+++ b/absl/flags/internal/flag.h
@@ -721,8 +721,9 @@ struct FlagRegistrarEmpty {};
 template <typename T, bool do_register>
 class FlagRegistrar {
  public:
-  explicit FlagRegistrar(Flag<T>& flag) : flag_(flag) {
-    if (do_register) flags_internal::RegisterCommandLineFlag(flag_.impl_);
+  explicit FlagRegistrar(Flag<T>& flag, const char* filename) : flag_(flag) {
+    if (do_register)
+      flags_internal::RegisterCommandLineFlag(flag_.impl_, filename);
   }
 
   FlagRegistrar OnUpdate(FlagCallbackFunc cb) && {
diff --git a/absl/flags/internal/registry.h b/absl/flags/internal/registry.h
index a8d9eb9c..4b68c85f 100644
--- a/absl/flags/internal/registry.h
+++ b/absl/flags/internal/registry.h
@@ -36,7 +36,7 @@ void ForEachFlag(std::function<void(CommandLineFlag&)> visitor);
 
 //-----------------------------------------------------------------------------
 
-bool RegisterCommandLineFlag(CommandLineFlag&);
+bool RegisterCommandLineFlag(CommandLineFlag&, const char* filename);
 
 void FinalizeRegistry();
 
diff --git a/absl/flags/reflection.cc b/absl/flags/reflection.cc
index c976d467..0c761101 100644
--- a/absl/flags/reflection.cc
+++ b/absl/flags/reflection.cc
@@ -50,7 +50,7 @@ class FlagRegistry {
   ~FlagRegistry() = default;
 
   // Store a flag in this registry. Takes ownership of *flag.
-  void RegisterFlag(CommandLineFlag& flag);
+  void RegisterFlag(CommandLineFlag& flag, const char* filename);
 
   void Lock() ABSL_EXCLUSIVE_LOCK_FUNCTION(lock_) { lock_.Lock(); }
   void Unlock() ABSL_UNLOCK_FUNCTION(lock_) { lock_.Unlock(); }
@@ -110,7 +110,20 @@ CommandLineFlag* FlagRegistry::FindFlag(absl::string_view name) {
   return it != flags_.end() ? it->second : nullptr;
 }
 
-void FlagRegistry::RegisterFlag(CommandLineFlag& flag) {
+void FlagRegistry::RegisterFlag(CommandLineFlag& flag, const char* filename) {
+  if (filename != nullptr &&
+      flag.Filename() != GetUsageConfig().normalize_filename(filename)) {
+    flags_internal::ReportUsageError(
+        absl::StrCat(
+            "Inconsistency between flag object and registration for flag '",
+            flag.Name(),
+            "', likely due to duplicate flags or an ODR violation. Relevant "
+            "files: ",
+            flag.Filename(), " and ", filename),
+        true);
+    std::exit(1);
+  }
+
   FlagRegistryLock registry_lock(*this);
 
   std::pair<FlagIterator, bool> ins =
@@ -175,8 +188,8 @@ void ForEachFlag(std::function<void(CommandLineFlag&)> visitor) {
 
 // --------------------------------------------------------------------
 
-bool RegisterCommandLineFlag(CommandLineFlag& flag) {
-  FlagRegistry::GlobalRegistry().RegisterFlag(flag);
+bool RegisterCommandLineFlag(CommandLineFlag& flag, const char* filename) {
+  FlagRegistry::GlobalRegistry().RegisterFlag(flag, filename);
   return true;
 }
 
@@ -266,7 +279,7 @@ void Retire(const char* name, FlagFastTypeId type_id, char* buf) {
   static_assert(alignof(RetiredFlagObj) == kRetiredFlagObjAlignment, "");
   auto* flag = ::new (static_cast<void*>(buf))
       flags_internal::RetiredFlagObj(name, type_id);
-  FlagRegistry::GlobalRegistry().RegisterFlag(*flag);
+  FlagRegistry::GlobalRegistry().RegisterFlag(*flag, nullptr);
 }
 
 // --------------------------------------------------------------------
diff --git a/absl/numeric/bits_test.cc b/absl/numeric/bits_test.cc
index 8bf7bc9f..7c942aae 100644
--- a/absl/numeric/bits_test.cc
+++ b/absl/numeric/bits_test.cc
@@ -560,6 +560,14 @@ TEST(IntegralPowersOfTwo, Width) {
   }
 }
 
+// On GCC and Clang, anticiapte that implementations will be constexpr
+#if defined(__GNUC__)
+static_assert(ABSL_INTERNAL_HAS_CONSTEXPR_POPCOUNT,
+              "popcount should be constexpr");
+static_assert(ABSL_INTERNAL_HAS_CONSTEXPR_CLZ, "clz should be constexpr");
+static_assert(ABSL_INTERNAL_HAS_CONSTEXPR_CTZ, "ctz should be constexpr");
+#endif
+
 }  // namespace
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/numeric/internal/bits.h b/absl/numeric/internal/bits.h
index af45700f..e51941d7 100644
--- a/absl/numeric/internal/bits.h
+++ b/absl/numeric/internal/bits.h
@@ -28,8 +28,15 @@
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
 
-#if ABSL_HAVE_BUILTIN(__builtin_popcountl) && \
-    ABSL_HAVE_BUILTIN(__builtin_popcountll)
+#if defined(__GNUC__) && !defined(__clang__)
+// GCC
+#define ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(x) 1
+#else
+#define ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(x) ABSL_HAVE_BUILTIN(x)
+#endif
+
+#if ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(__builtin_popcountl) && \
+    ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(__builtin_popcountll)
 #define ABSL_INTERNAL_CONSTEXPR_POPCOUNT constexpr
 #define ABSL_INTERNAL_HAS_CONSTEXPR_POPCOUNT 1
 #else
@@ -37,7 +44,8 @@
 #define ABSL_INTERNAL_HAS_CONSTEXPR_POPCOUNT 0
 #endif
 
-#if ABSL_HAVE_BUILTIN(__builtin_clz) && ABSL_HAVE_BUILTIN(__builtin_clzll)
+#if ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(__builtin_clz) && \
+    ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(__builtin_clzll)
 #define ABSL_INTERNAL_CONSTEXPR_CLZ constexpr
 #define ABSL_INTERNAL_HAS_CONSTEXPR_CLZ 1
 #else
@@ -45,7 +53,8 @@
 #define ABSL_INTERNAL_HAS_CONSTEXPR_CLZ 0
 #endif
 
-#if ABSL_HAVE_BUILTIN(__builtin_ctz) && ABSL_HAVE_BUILTIN(__builtin_ctzll)
+#if ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(__builtin_ctz) && \
+    ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(__builtin_ctzll)
 #define ABSL_INTERNAL_CONSTEXPR_CTZ constexpr
 #define ABSL_INTERNAL_HAS_CONSTEXPR_CTZ 1
 #else
@@ -85,7 +94,7 @@ ABSL_MUST_USE_RESULT ABSL_ATTRIBUTE_ALWAYS_INLINE constexpr T RotateLeft(
 
 ABSL_ATTRIBUTE_ALWAYS_INLINE ABSL_INTERNAL_CONSTEXPR_POPCOUNT inline int
 Popcount32(uint32_t x) noexcept {
-#if ABSL_HAVE_BUILTIN(__builtin_popcount)
+#if ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(__builtin_popcount)
   static_assert(sizeof(unsigned int) == sizeof(x),
                 "__builtin_popcount does not take 32-bit arg");
   return __builtin_popcount(x);
@@ -98,7 +107,7 @@ Popcount32(uint32_t x) noexcept {
 
 ABSL_ATTRIBUTE_ALWAYS_INLINE ABSL_INTERNAL_CONSTEXPR_POPCOUNT inline int
 Popcount64(uint64_t x) noexcept {
-#if ABSL_HAVE_BUILTIN(__builtin_popcountll)
+#if ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(__builtin_popcountll)
   static_assert(sizeof(unsigned long long) == sizeof(x),  // NOLINT(runtime/int)
                 "__builtin_popcount does not take 64-bit arg");
   return __builtin_popcountll(x);
@@ -122,7 +131,7 @@ Popcount(T x) noexcept {
 
 ABSL_ATTRIBUTE_ALWAYS_INLINE ABSL_INTERNAL_CONSTEXPR_CLZ inline int
 CountLeadingZeroes32(uint32_t x) {
-#if ABSL_HAVE_BUILTIN(__builtin_clz)
+#if ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(__builtin_clz)
   // Use __builtin_clz, which uses the following instructions:
   //  x86: bsr, lzcnt
   //  ARM64: clz
@@ -169,7 +178,7 @@ CountLeadingZeroes16(uint16_t x) {
 
 ABSL_ATTRIBUTE_ALWAYS_INLINE ABSL_INTERNAL_CONSTEXPR_CLZ inline int
 CountLeadingZeroes64(uint64_t x) {
-#if ABSL_HAVE_BUILTIN(__builtin_clzll)
+#if ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(__builtin_clzll)
   // Use __builtin_clzll, which uses the following instructions:
   //  x86: bsr, lzcnt
   //  ARM64: clz
@@ -240,7 +249,7 @@ CountLeadingZeroes(T x) {
 
 ABSL_ATTRIBUTE_ALWAYS_INLINE ABSL_INTERNAL_CONSTEXPR_CTZ inline int
 CountTrailingZeroesNonzero32(uint32_t x) {
-#if ABSL_HAVE_BUILTIN(__builtin_ctz)
+#if ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(__builtin_ctz)
   static_assert(sizeof(unsigned int) == sizeof(x),
                 "__builtin_ctz does not take 32-bit arg");
   return __builtin_ctz(x);
@@ -262,7 +271,7 @@ CountTrailingZeroesNonzero32(uint32_t x) {
 
 ABSL_ATTRIBUTE_ALWAYS_INLINE ABSL_INTERNAL_CONSTEXPR_CTZ inline int
 CountTrailingZeroesNonzero64(uint64_t x) {
-#if ABSL_HAVE_BUILTIN(__builtin_ctzll)
+#if ABSL_NUMERIC_INTERNAL_HAVE_BUILTIN_OR_GCC(__builtin_ctzll)
   static_assert(sizeof(unsigned long long) == sizeof(x),  // NOLINT(runtime/int)
                 "__builtin_ctzll does not take 64-bit arg");
   return __builtin_ctzll(x);
diff --git a/absl/synchronization/mutex.cc b/absl/synchronization/mutex.cc
index d2468ce5..7e66a7d0 100644
--- a/absl/synchronization/mutex.cc
+++ b/absl/synchronization/mutex.cc
@@ -1372,7 +1372,9 @@ static GraphId DeadlockCheck(Mutex *mu) {
           len += static_cast<int>(strlen(&b->buf[len]));
         }
       }
-      ABSL_RAW_LOG(ERROR, "Acquiring %p    Mutexes held: %s",
+      ABSL_RAW_LOG(ERROR,
+                   "Acquiring absl::Mutex %p while holding %s; a cycle in the "
+                   "historical lock ordering graph has been observed",
                    static_cast<void *>(mu), b->buf);
       ABSL_RAW_LOG(ERROR, "Cycle: ");
       int path_len = deadlock_graph->FindPath(