- abe587c2360b21f085b7d65a77d840015bc04cf6 Factor an internal interface into its own header, as it w... by Greg Falcon <gfalcon@google.com>

  - 2201f1644336e64280dbd20207d8fbc3bfea2bf4 Internal change. by Abseil Team <absl-team@google.com>
  - 94e6b5b20d2cc754c99a18c575a4f1f3cd1f28d4 Rename no_throw_ctor to nothrow_ctor to match the standar... by Abseil Team <absl-team@google.com>
  - 86aa34d2129c4914c5133b7b619480aae786288e Update header files in debugging target by Tom Manshreck <shreck@google.com>
  - ed234519ced458724a7267b8fdf184eaae1c97c7 Remove CMAKE_CXX_WARNING_VLA from our c++ flags in the cm... by Jon Cohen <cohenjon@google.com>

GitOrigin-RevId: abe587c2360b21f085b7d65a77d840015bc04cf6
Change-Id: I92f9301c69419d3830c358b88984967185aa33f6

13 files changed, 279 insertions, 117 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1a8f8622..744241ef 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -53,7 +53,6 @@ list(APPEND ABSL_COMMON_INCLUDE_DIRS ${CMAKE_CURRENT_SOURCE_DIR})
 
 # -std=X
 set(CMAKE_CXX_FLAGS "${ABSL_STD_CXX_FLAG} ${CMAKE_CXX_FLAGS}")
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_WARNING_VLA} ${CMAKE_CXX_FLAGS} ")
 
 # -fexceptions
 set(ABSL_EXCEPTIONS_FLAG "${CMAKE_CXX_EXCEPTIONS}")
diff --git a/absl/base/exception_safety_testing_test.cc b/absl/base/exception_safety_testing_test.cc
index 4507b946..a8b82b73 100644
--- a/absl/base/exception_safety_testing_test.cc
+++ b/absl/base/exception_safety_testing_test.cc
@@ -405,7 +405,7 @@ TEST(ThrowingAllocatorTest, NonThrowingConstruction) {
 
     SetCountdown();
     ExpectNoThrow(
-        [&]() { nothrow_alloc.construct(ptr, 2, testing::no_throw_ctor); });
+        [&]() { nothrow_alloc.construct(ptr, 2, testing::nothrow_ctor); });
 
     EXPECT_EQ(ptr->Get(), 2);
     nothrow_alloc.destroy(ptr);
diff --git a/absl/base/internal/exception_safety_testing.cc b/absl/base/internal/exception_safety_testing.cc
index c92d07bc..d3e94074 100644
--- a/absl/base/internal/exception_safety_testing.cc
+++ b/absl/base/internal/exception_safety_testing.cc
@@ -19,7 +19,12 @@
 
 namespace testing {
 
-exceptions_internal::NoThrowTag no_throw_ctor;
+exceptions_internal::NoThrowTag nothrow_ctor;
+
+bool nothrow_guarantee(const void*) {
+  return ::testing::AssertionFailure()
+         << "Exception thrown violating NoThrow Guarantee";
+}
 exceptions_internal::StrongGuaranteeTagType strong_guarantee;
 
 namespace exceptions_internal {
diff --git a/absl/base/internal/exception_safety_testing.h b/absl/base/internal/exception_safety_testing.h
index bec3ab30..c3ff34c5 100644
--- a/absl/base/internal/exception_safety_testing.h
+++ b/absl/base/internal/exception_safety_testing.h
@@ -227,7 +227,9 @@ inline absl::optional<testing::AssertionResult> TestAllInvariantsAtCountdown(
 
 }  // namespace exceptions_internal
 
-extern exceptions_internal::NoThrowTag no_throw_ctor;
+extern exceptions_internal::NoThrowTag nothrow_ctor;
+
+bool nothrow_guarantee(const void*);
 extern exceptions_internal::StrongGuaranteeTagType strong_guarantee;
 
 // A test class which is convertible to bool.  The conversion can be
@@ -246,7 +248,7 @@ class ThrowingBool {
 
 /*
  * Configuration enum for the ThrowingValue type that defines behavior for the
- * lifetime of the instance. Use testing::no_throw_ctor to prevent the integer
+ * lifetime of the instance. Use testing::nothrow_ctor to prevent the integer
  * constructor from throwing.
  *
  * kEverythingThrows: Every operation can throw an exception
@@ -341,22 +343,22 @@ class ThrowingValue : private exceptions_internal::TrackedObject {
   // Arithmetic Operators
   ThrowingValue operator+(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ + other.dummy_, no_throw_ctor);
+    return ThrowingValue(dummy_ + other.dummy_, nothrow_ctor);
   }
 
   ThrowingValue operator+() const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_, no_throw_ctor);
+    return ThrowingValue(dummy_, nothrow_ctor);
   }
 
   ThrowingValue operator-(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ - other.dummy_, no_throw_ctor);
+    return ThrowingValue(dummy_ - other.dummy_, nothrow_ctor);
   }
 
   ThrowingValue operator-() const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(-dummy_, no_throw_ctor);
+    return ThrowingValue(-dummy_, nothrow_ctor);
   }
 
   ThrowingValue& operator++() {
@@ -367,7 +369,7 @@ class ThrowingValue : private exceptions_internal::TrackedObject {
 
   ThrowingValue operator++(int) {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    auto out = ThrowingValue(dummy_, no_throw_ctor);
+    auto out = ThrowingValue(dummy_, nothrow_ctor);
     ++dummy_;
     return out;
   }
@@ -380,34 +382,34 @@ class ThrowingValue : private exceptions_internal::TrackedObject {
 
   ThrowingValue operator--(int) {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    auto out = ThrowingValue(dummy_, no_throw_ctor);
+    auto out = ThrowingValue(dummy_, nothrow_ctor);
     --dummy_;
     return out;
   }
 
   ThrowingValue operator*(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ * other.dummy_, no_throw_ctor);
+    return ThrowingValue(dummy_ * other.dummy_, nothrow_ctor);
   }
 
   ThrowingValue operator/(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ / other.dummy_, no_throw_ctor);
+    return ThrowingValue(dummy_ / other.dummy_, nothrow_ctor);
   }
 
   ThrowingValue operator%(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ % other.dummy_, no_throw_ctor);
+    return ThrowingValue(dummy_ % other.dummy_, nothrow_ctor);
   }
 
   ThrowingValue operator<<(int shift) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ << shift, no_throw_ctor);
+    return ThrowingValue(dummy_ << shift, nothrow_ctor);
   }
 
   ThrowingValue operator>>(int shift) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ >> shift, no_throw_ctor);
+    return ThrowingValue(dummy_ >> shift, nothrow_ctor);
   }
 
   // Comparison Operators
@@ -463,22 +465,22 @@ class ThrowingValue : private exceptions_internal::TrackedObject {
   // Bitwise Logical Operators
   ThrowingValue operator~() const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(~dummy_, no_throw_ctor);
+    return ThrowingValue(~dummy_, nothrow_ctor);
   }
 
   ThrowingValue operator&(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ & other.dummy_, no_throw_ctor);
+    return ThrowingValue(dummy_ & other.dummy_, nothrow_ctor);
   }
 
   ThrowingValue operator|(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ | other.dummy_, no_throw_ctor);
+    return ThrowingValue(dummy_ | other.dummy_, nothrow_ctor);
   }
 
   ThrowingValue operator^(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ ^ other.dummy_, no_throw_ctor);
+    return ThrowingValue(dummy_ ^ other.dummy_, nothrow_ctor);
   }
 
   // Compound Assignment operators
@@ -1034,12 +1036,6 @@ MakeExceptionSafetyTester() {
   return {};
 }
 
-// Always return false, intended to be used as a checker with
-// TestExceptionSafety() to check that no exception is thrown.
-inline bool nothrow_guarantee(const void*) {
-  return ::testing::AssertionFailure() << "Violating NoThrowGuarantee";
-}
-
 }  // namespace testing
 
 #endif  // ABSL_BASE_INTERNAL_EXCEPTION_SAFETY_TESTING_H_
diff --git a/absl/debugging/leak_check.h b/absl/debugging/leak_check.h
index f67fe88a..c930684e 100644
--- a/absl/debugging/leak_check.h
+++ b/absl/debugging/leak_check.h
@@ -1,5 +1,4 @@
-//
-// Copyright 2017 The Abseil Authors.
+// Copyright 2018 The Abseil Authors.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -13,15 +12,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 //
-
 // -----------------------------------------------------------------------------
 // File: leak_check.h
 // -----------------------------------------------------------------------------
 //
-// This package contains functions that affect leak checking behavior within
+// This file contains functions that affect leak checking behavior within
 // targets built with the LeakSanitizer (LSan), a memory leak detector that is
 // integrated within the AddressSanitizer (ASan) as an additional component, or
-// which can be used standalone. LSan and ASan are included or can be provided
+// which can be used standalone. LSan and ASan are included (or can be provided)
 // as additional components for most compilers such as Clang, gcc and MSVC.
 // Note: this leak checking API is not yet supported in MSVC.
 // Leak checking is enabled by default in all ASan builds.
diff --git a/absl/debugging/stacktrace.h b/absl/debugging/stacktrace.h
index 82da3f15..8b831e26 100644
--- a/absl/debugging/stacktrace.h
+++ b/absl/debugging/stacktrace.h
@@ -1,5 +1,4 @@
-//
-// Copyright 2017 The Abseil Authors.
+// Copyright 2018 The Abseil Authors.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -13,26 +12,37 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 //
-
-// Routines to extract the current stack trace. These functions are
-// thread-safe and async-signal-safe.
+// -----------------------------------------------------------------------------
+// File: stacktrace.h
+// -----------------------------------------------------------------------------
+//
+// This file contains routines to extract the current stack trace and associated
+// stack frames. These functions are thread-safe and async-signal-safe.
+//
 // Note that stack trace functionality is platform dependent and requires
-// additional support from the compiler/build system in many cases. (That is,
-// this generally only works on platforms/builds that have been specifically
-// configured to support it.)
+// additional support from the compiler/build system in most cases. (That is,
+// this functionality generally only works on platforms/builds that have been
+// specifically configured to support it.)
+//
+// Note: stack traces in Abseil that do not utilize a symbolizer will result in
+// frames consisting of function addresses rather than human-readable function
+// names. (See symbolize.h for information on symbolizing these values.)
 
 #ifndef ABSL_DEBUGGING_STACKTRACE_H_
 #define ABSL_DEBUGGING_STACKTRACE_H_
 
 namespace absl {
 
-// Skips the most recent "skip_count" stack frames (also skips the
-// frame generated for the "absl::GetStackFrames" routine itself), and then
-// records the pc values for up to the next "max_depth" frames in
-// "result", and the corresponding stack frame sizes in "sizes".
-// Returns the number of values recorded in "result"/"sizes".
+// GetStackFrames()
+//
+// Records program counter values for up to `max_depth` frames, skipping the
+// most recent `skip_count` stack frames, and stores their corresponding values
+// and sizes in `results` and `sizes` buffers. (Note that the frame generated
+// for the `absl::GetStackFrames()` routine itself is also skipped.)
+// routine itself.
 //
 // Example:
+//
 //      main() { foo(); }
 //      foo() { bar(); }
 //      bar() {
@@ -41,41 +51,66 @@ namespace absl {
 //        int depth = absl::GetStackFrames(result, sizes, 10, 1);
 //      }
 //
-// The absl::GetStackFrames call will skip the frame for "bar".  It will
-// return 2 and will produce pc values that map to the following
-// procedures:
-//      result[0]       foo
-//      result[1]       main
-// (Actually, there may be a few more entries after "main" to account for
-// startup procedures.)
-// And corresponding stack frame sizes will also be recorded:
+// The current stack frame would consist of three function calls: `bar()`,
+// `foo()`, and then `main()`; however, since the `GetStackFrames()` call sets
+// `skip_count` to `1`, it will skip the frame for `bar()`, the most recently
+// invoked function call. It will therefore return two program counters and will
+// produce values that map to the following function calls:
+//
+//      result[0]       foo()
+//      result[1]       main()
+//
+// (Note: in practice, a few more entries after `main()` may be added to account
+// for startup processes.)
+//
+// Corresponding stack frame sizes will also be recorded:
+//
 //    sizes[0]       16
 //    sizes[1]       16
-// (Stack frame sizes of 16 above are just for illustration purposes.)
+//
+// (Stack frame sizes of `16` above are just for illustration purposes.)
+//
 // Stack frame sizes of 0 or less indicate that those frame sizes couldn't
 // be identified.
 //
 // This routine may return fewer stack frame entries than are
-// available. Also note that "result" and "sizes" must both be non-null.
+// available. Also note that `result` and `sizes` must both be non-null.
 extern int GetStackFrames(void** result, int* sizes, int max_depth,
                           int skip_count);
 
-// Same as above, but to be used from a signal handler. The "uc" parameter
-// should be the pointer to ucontext_t which was passed as the 3rd parameter
-// to sa_sigaction signal handler. It may help the unwinder to get a
-// better stack trace under certain conditions. The "uc" may safely be null.
-//
-// If min_dropped_frames is not null, stores in *min_dropped_frames a
-// lower bound on the number of dropped stack frames. The stored value is
-// guaranteed to be >= 0. The number of real stack frames is guaranteed to
-// be >= skip_count + max_depth + *min_dropped_frames.
+// GetStackFramesWithContext()
+//
+// Records program counter values obtained from a signal handler. Records
+// program counter values for up to `max_depth` frames, skipping the most recent
+// `skip_count` stack frames, and stores their corresponding values and sizes in
+// `results` and `sizes` buffers. (Note that the frame generated for the
+// `absl::GetStackFramesWithContext()` routine itself is also skipped.)
+//
+// The `uc` parameter, if non-null, should be a pointer to a `ucontext_t` value
+// passed to a signal handler registered via the `sa_sigaction` field of a
+// `sigaction` struct. (See
+// http://man7.org/linux/man-pages/man2/sigaction.2.html.) The `uc` value may
+// help a stack unwinder to provide a better stack trace under certain
+// conditions. `uc` may safely be null.
+//
+// The `min_dropped_frames` output parameter, if non-null, points to the
+// location to note any dropped stack frames, if any, due to buffer limitations
+// or other reasons. (This value will be set to `0` if no frames were dropped.)
+// The number of total stack frames is guaranteed to be >= skip_count +
+// max_depth + *min_dropped_frames.
 extern int GetStackFramesWithContext(void** result, int* sizes, int max_depth,
                                      int skip_count, const void* uc,
                                      int* min_dropped_frames);
 
-// This is similar to the absl::GetStackFrames routine, except that it returns
-// the stack trace only, and not the stack frame sizes as well.
+// GetStackTrace()
+//
+// Records program counter values for up to `max_depth` frames, skipping the
+// most recent `skip_count` stack frames, and stores their corresponding values
+// in `results`. Note that this function is similar to `absl::GetStackFrames()`
+// except that it returns the stack trace only, and not stack frame sizes.
+//
 // Example:
+//
 //      main() { foo(); }
 //      foo() { bar(); }
 //      bar() {
@@ -84,42 +119,57 @@ extern int GetStackFramesWithContext(void** result, int* sizes, int max_depth,
 //      }
 //
 // This produces:
+//
 //      result[0]       foo
 //      result[1]       main
 //           ....       ...
 //
-// "result" must not be null.
+// `result` must not be null.
 extern int GetStackTrace(void** result, int max_depth, int skip_count);
 
-// Same as above, but to be used from a signal handler. The "uc" parameter
-// should be the pointer to ucontext_t which was passed as the 3rd parameter
-// to sa_sigaction signal handler. It may help the unwinder to get a
-// better stack trace under certain conditions. The "uc" may safely be null.
-//
-// If min_dropped_frames is not null, stores in *min_dropped_frames a
-// lower bound on the number of dropped stack frames. The stored value is
-// guaranteed to be >= 0. The number of real stack frames is guaranteed to
-// be >= skip_count + max_depth + *min_dropped_frames.
+// GetStackTraceWithContext()
+//
+// Records program counter values obtained from a signal handler. Records
+// program counter values for up to `max_depth` frames, skipping the most recent
+// `skip_count` stack frames, and stores their corresponding values in
+// `results`. (Note that the frame generated for the
+// `absl::GetStackFramesWithContext()` routine itself is also skipped.)
+//
+// The `uc` parameter, if non-null, should be a pointer to a `ucontext_t` value
+// passed to a signal handler registered via the `sa_sigaction` field of a
+// `sigaction` struct. (See
+// http://man7.org/linux/man-pages/man2/sigaction.2.html.) The `uc` value may
+// help a stack unwinder to provide a better stack trace under certain
+// conditions. `uc` may safely be null.
+//
+// The `min_dropped_frames` output parameter, if non-null, points to the
+// location to note any dropped stack frames, if any, due to buffer limitations
+// or other reasons. (This value will be set to `0` if no frames were dropped.)
+// The number of total stack frames is guaranteed to be >= skip_count +
+// max_depth + *min_dropped_frames.
 extern int GetStackTraceWithContext(void** result, int max_depth,
                                     int skip_count, const void* uc,
                                     int* min_dropped_frames);
 
-// Call this to provide a custom function for unwinding stack frames
-// that will be used every time someone invokes one of the static
+// SetStackUnwinder()
+//
+// Provides a custom function for unwinding stack frames that will be used in
+// place of the default stack unwinder when invoking the static
 // GetStack{Frames,Trace}{,WithContext}() functions above.
 //
 // The arguments passed to the unwinder function will match the
-// arguments passed to absl::GetStackFramesWithContext() except that sizes
+// arguments passed to `absl::GetStackFramesWithContext()` except that sizes
 // will be non-null iff the caller is interested in frame sizes.
 //
-// If unwinder is null, we revert to the default stack-tracing behavior.
+// If unwinder is set to null, we revert to the default stack-tracing behavior.
 //
-// ****************************************************************
-// WARNINGS
+// *****************************************************************************
+// WARNING
+// *****************************************************************************
 //
 // absl::SetStackUnwinder is not suitable for general purpose use.  It is
 // provided for custom runtimes.
-// Some things to watch out for when calling absl::SetStackUnwinder:
+// Some things to watch out for when calling `absl::SetStackUnwinder()`:
 //
 // (a) The unwinder may be called from within signal handlers and
 // therefore must be async-signal-safe.
@@ -128,23 +178,31 @@ extern int GetStackTraceWithContext(void** result, int max_depth,
 // threads may still be in the process of using that unwinder.
 // Therefore do not clean up any state that may be needed by an old
 // unwinder.
-// ****************************************************************
+// *****************************************************************************
 extern void SetStackUnwinder(int (*unwinder)(void** pcs, int* sizes,
                                              int max_depth, int skip_count,
                                              const void* uc,
                                              int* min_dropped_frames));
 
-// Function that exposes built-in stack-unwinding behavior, ignoring
-// any calls to absl::SetStackUnwinder().
+// DefaultStackUnwinder()
+//
+// Records program counter values of up to `max_depth` frames, skipping the most
+// recent `skip_count` stack frames, and stores their corresponding values in
+// `pcs`. (Note that the frame generated for this call itself is also skipped.)
+// This function acts as a generic stack-unwinder; prefer usage of the more
+// specific `GetStack{Trace,Frames}{,WithContext}()` functions above.
 //
-// pcs must NOT be null.
+// If you have set your own stack unwinder (with the `SetStackUnwinder()`
+// function above, you can still get the default stack unwinder by calling
+// `DefaultStackUnwinder()`, which will ignore any previously set stack unwinder
+// and use the default one instead.
 //
-// sizes may be null.
-// uc may be null.
-// min_dropped_frames may be null.
+// Because this function is generic, only `pcs` is guaranteed to be non-null
+// upon return. It is legal for `sizes`, `uc`, and `min_dropped_frames` to all
+// be null when called.
 //
-// The semantics are the same as the corresponding GetStack*() function in the
-// case where absl::SetStackUnwinder() was never called.  Equivalents are:
+// The semantics are the same as the corresponding `GetStack*()` function in the
+// case where `absl::SetStackUnwinder()` was never called. Equivalents are:
 //
 //                       null sizes         |        non-nullptr sizes
 //             |==========================================================|
diff --git a/absl/debugging/symbolize.h b/absl/debugging/symbolize.h
index 073a4479..24e6e647 100644
--- a/absl/debugging/symbolize.h
+++ b/absl/debugging/symbolize.h
@@ -11,7 +11,44 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-
+//
+// -----------------------------------------------------------------------------
+// File: symbolize.h
+// -----------------------------------------------------------------------------
+//
+// This file configures the Abseil symbolizer for use in converting instruction
+// pointer addresses (program counters) into human-readable names (function
+// calls, etc.) within Abseil code.
+//
+// The symbolizer may be invoked from several sources:
+//
+//   * Implicitly, through the installation of an Abseil failure signal handler.
+//     (See failure_signal_handler.h for more information.)
+//   * By calling `Symbolize()` directly on a program counter you obtain through
+//     `absl::GetStackTrace()` or `absl::GetStackFrames()`. (See stacktrace.h
+//     for more information.
+//   * By calling `Symbolize()` directly on a program counter you obtain through
+//     other means (which would be platform-dependent).
+//
+// In all of the above cases, the symbolizer must first be initialized before
+// any program counter values can be symbolized. If you are installing a failure
+// signal handler, initialize the symbolizer before you do so.
+//
+// Example:
+//
+//   int main(int argc, char** argv) {
+//     // Initialize the Symbolizer before installing the failure signal handler
+//     absl::InitializeSymbolizer(argv[0]);
+//
+//     // Now you may install the failure signal handler
+//     absl::FailureSignalHandlerOptions options;
+//     absl::InstallFailureSignalHandler(options);
+//
+//     // Start running your main program
+//     ...
+//     return 0;
+//  }
+//
 #ifndef ABSL_DEBUGGING_SYMBOLIZE_H_
 #define ABSL_DEBUGGING_SYMBOLIZE_H_
 
@@ -19,15 +56,40 @@
 
 namespace absl {
 
-// Initializes this module. Symbolize() may fail prior calling this function.
-// `argv0` is the path to this program, which is usually obtained in main()
-// though argv[0].
+// InitializeSymbolizer()
+//
+// Initializes the program counter symbolizer, given the path of the program
+// (typically obtained through `main()`s `argv[0]`). The Abseil symbolizer
+// allows you to read program counters (instruction pointer values) using their
+// human-readable names within output such as stack traces.
+//
+// Example:
+//
+// int main(int argc, char *argv[]) {
+//   absl::InitializeSymbolizer(argv[0]);
+//   // Now you can use the symbolizer
+// }
 void InitializeSymbolizer(const char* argv0);
 
-// Symbolizes a program counter.  On success, returns true and write the
-// symbol name to "out".  The symbol name is demangled if possible
-// (supports symbols generated by GCC 3.x or newer), may be truncated, and
-// will be '\0' terminated.  Otherwise, returns false.
+// Symbolize()
+//
+// Symbolizes a program counter (instruction pointer value) `pc` and, on
+// success, writes the name to `out`. The symbol name is demangled, if possible.
+// Note that the symbolized name may be truncated and will be NUL-terminated.
+// Demangling is supported for symbols generated by GCC 3.x or newer). Returns
+// `false` on failure.
+//
+// Example:
+//
+//   // Print a program counter and its symbol name.
+//   static void DumpPCAndSymbol(void *pc) {
+//     char tmp[1024];
+//     const char *symbol = "(unknown)";
+//     if (absl::Symbolize(pc, tmp, sizeof(tmp))) {
+//       symbol = tmp;
+//     }
+//     absl::PrintF("%*p  %s\n", pc, symbol);
+//  }
 bool Symbolize(const void *pc, char *out, int out_size);
 
 }  // namespace absl
diff --git a/absl/strings/BUILD.bazel b/absl/strings/BUILD.bazel
index 13badb7b..1e52312b 100644
--- a/absl/strings/BUILD.bazel
+++ b/absl/strings/BUILD.bazel
@@ -84,6 +84,7 @@ cc_library(
         "internal/utf8.cc",
     ],
     hdrs = [
+        "internal/bits.h",
         "internal/char_map.h",
         "internal/ostringstream.h",
         "internal/resize_uninitialized.h",
diff --git a/absl/strings/CMakeLists.txt b/absl/strings/CMakeLists.txt
index 83cb934d..9dc47328 100644
--- a/absl/strings/CMakeLists.txt
+++ b/absl/strings/CMakeLists.txt
@@ -31,6 +31,7 @@ list(APPEND STRINGS_PUBLIC_HEADERS
 
 
 list(APPEND STRINGS_INTERNAL_HEADERS
+  "internal/bits.h"
   "internal/char_map.h"
   "internal/memutil.h"
   "internal/ostringstream.h"
diff --git a/absl/strings/internal/bits.h b/absl/strings/internal/bits.h
new file mode 100644
index 00000000..901082cc
--- /dev/null
+++ b/absl/strings/internal/bits.h
@@ -0,0 +1,53 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_STRINGS_INTERNAL_BITS_H_
+#define ABSL_STRINGS_INTERNAL_BITS_H_
+
+#include <cstdint>
+
+#if defined(_MSC_VER) && defined(_M_X64)
+#include <intrin.h>
+#pragma intrinsic(_BitScanReverse64)
+#endif
+
+namespace absl {
+namespace strings_internal {
+
+// Returns the number of leading 0 bits in a 64-bit value.
+inline int CountLeadingZeros64(uint64_t n) {
+#if defined(__GNUC__)
+  static_assert(sizeof(unsigned long long) == sizeof(n),  // NOLINT(runtime/int)
+                "__builtin_clzll does not take 64bit arg");
+  return n == 0 ? 64 : __builtin_clzll(n);
+#elif defined(_MSC_VER) && defined(_M_X64)
+  unsigned long result;  // NOLINT(runtime/int)
+  if (_BitScanReverse64(&result, n)) {
+    return 63 - result;
+  }
+  return 64;
+#else
+  int zeroes = 60;
+  if (n >> 32) zeroes -= 32, n >>= 32;
+  if (n >> 16) zeroes -= 16, n >>= 16;
+  if (n >> 8) zeroes -= 8, n >>= 8;
+  if (n >> 4) zeroes -= 4, n >>= 4;
+  return "\4\3\2\2\1\1\1\1\0\0\0\0\0\0\0\0"[n] + zeroes;
+#endif
+}
+
+}  // namespace strings_internal
+}  // namespace absl
+
+#endif  // ABSL_STRINGS_INTERNAL_BITS_H_
diff --git a/absl/strings/numbers.cc b/absl/strings/numbers.cc
index b4140b36..68ef7999 100644
--- a/absl/strings/numbers.cc
+++ b/absl/strings/numbers.cc
@@ -32,6 +32,7 @@
 
 #include "absl/base/internal/raw_logging.h"
 #include "absl/strings/ascii.h"
+#include "absl/strings/internal/bits.h"
 #include "absl/strings/internal/memutil.h"
 #include "absl/strings/str_cat.h"
 
@@ -302,18 +303,6 @@ char* numbers_internal::FastIntToBuffer(int64_t i, char* buffer) {
   return numbers_internal::FastIntToBuffer(u, buffer);
 }
 
-// Returns the number of leading 0 bits in a 64-bit value.
-// TODO(jorg): Replace with builtin_clzll if available.
-// Are we shipping util/bits in absl?
-static inline int CountLeadingZeros64(uint64_t n) {
-  int zeroes = 60;
-  if (n >> 32) zeroes -= 32, n >>= 32;
-  if (n >> 16) zeroes -= 16, n >>= 16;
-  if (n >> 8) zeroes -= 8, n >>= 8;
-  if (n >> 4) zeroes -= 4, n >>= 4;
-  return "\4\3\2\2\1\1\1\1\0\0\0\0\0\0\0\0"[n] + zeroes;
-}
-
 // Given a 128-bit number expressed as a pair of uint64_t, high half first,
 // return that number multiplied by the given 32-bit value.  If the result is
 // too large to fit in a 128-bit number, divide it by 2 until it fits.
@@ -351,7 +340,7 @@ static std::pair<uint64_t, uint64_t> Mul32(std::pair<uint64_t, uint64_t> num,
   uint64_t bits128_up = (bits96_127 >> 32) + (bits64_127 < bits64_95);
   if (bits128_up == 0) return {bits64_127, bits0_63};
 
-  int shift = 64 - CountLeadingZeros64(bits128_up);
+  int shift = 64 - strings_internal::CountLeadingZeros64(bits128_up);
   uint64_t lo = (bits0_63 >> shift) + (bits64_127 << (64 - shift));
   uint64_t hi = (bits64_127 >> shift) + (bits128_up << (64 - shift));
   return {hi, lo};
@@ -382,7 +371,7 @@ static std::pair<uint64_t, uint64_t> PowFive(uint64_t num, int expfive) {
       5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5,
       5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5};
   result = Mul32(result, powers_of_five[expfive & 15]);
-  int shift = CountLeadingZeros64(result.first);
+  int shift = strings_internal::CountLeadingZeros64(result.first);
   if (shift != 0) {
     result.first = (result.first << shift) + (result.second >> (64 - shift));
     result.second = (result.second << shift);
diff --git a/absl/synchronization/CMakeLists.txt b/absl/synchronization/CMakeLists.txt
index 6886c1ca..c19f5725 100644
--- a/absl/synchronization/CMakeLists.txt
+++ b/absl/synchronization/CMakeLists.txt
@@ -33,7 +33,7 @@ list(APPEND SYNCHRONIZATION_INTERNAL_HEADERS
 
 
 
-# syncrhonisation library
+# synchronization library
 list(APPEND SYNCHRONIZATION_SRC 
   "barrier.cc"
   "blocking_counter.cc"
diff --git a/absl/types/any_exception_safety_test.cc b/absl/types/any_exception_safety_test.cc
index daa82e72..36955f6c 100644
--- a/absl/types/any_exception_safety_test.cc
+++ b/absl/types/any_exception_safety_test.cc
@@ -99,7 +99,7 @@ TEST(AnyExceptionSafety, Ctors) {
 
 TEST(AnyExceptionSafety, Assignment) {
   auto original =
-      absl::any(absl::in_place_type_t<Thrower>(), 1, testing::no_throw_ctor);
+      absl::any(absl::in_place_type_t<Thrower>(), 1, testing::nothrow_ctor);
   auto any_is_strong = [original](absl::any* ap) {
     return testing::AssertionResult(ap->has_value() &&
                                     absl::any_cast<Thrower>(original) ==
@@ -139,14 +139,14 @@ TEST(AnyExceptionSafety, Assignment) {
 #if !defined(ABSL_HAVE_STD_ANY)
 TEST(AnyExceptionSafety, Emplace) {
   auto initial_val =
-      absl::any{absl::in_place_type_t<Thrower>(), 1, testing::no_throw_ctor};
+      absl::any{absl::in_place_type_t<Thrower>(), 1, testing::nothrow_ctor};
   auto one_tester = testing::MakeExceptionSafetyTester()
                         .WithInitialValue(initial_val)
                         .WithInvariants(AnyInvariants, AnyIsEmpty);
 
   auto emp_thrower = [](absl::any* ap) { ap->emplace<Thrower>(2); };
   auto emp_throwervec = [](absl::any* ap) {
-    std::initializer_list<Thrower> il{Thrower(2, testing::no_throw_ctor)};
+    std::initializer_list<Thrower> il{Thrower(2, testing::nothrow_ctor)};
     ap->emplace<ThrowerVec>(il);
   };
   auto emp_movethrower = [](absl::any* ap) {