Export of internal Abseil changes.

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cd076f55c1fa600131f6dda392533dfe61679fc0 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 224008762

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e05f62b01286d51044ff86ec6ef565749b9faf82 by Abseil Team <absl-team@google.com>:

Create a pow10() test helper function to compute guaranteed-precise double values of 10^x. Not all standard libraries ship bit-accurate pow() functions, causing tests to fail that rely on expected values generated by it.

PiperOrigin-RevId: 223883762

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fd88e5e3f7ab80f7f5df9fd1488cd58b4573be69 by Abseil Team <absl-team@google.com>:

Remove some absl:: qualifications to work around inline namespace bugs on MSVC 2015.

PiperOrigin-RevId: 223869642

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6276cfff969d596edd36a2bbaba65ee045808903 by Abseil Team <absl-team@google.com>:

Update absl/memory/CMakeLists.txt to use new functions
i.e. absl_cc_(library|test)

PiperOrigin-RevId: 223854224

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359de9afc7a34c975fd3e0cbc52afd96637d97bd by Chris Kennelly <ckennelly@google.com>:

Mark spinlock_benchmark_common as alwayslink = 1.

PiperOrigin-RevId: 223844536

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450cd8cbe2789a6d54ed1eb87170259bb334f8b9 by Abseil Team <absl-team@google.com>:

Support .* (pointer-to-member dereference) expressions in demangle.cc.

PiperOrigin-RevId: 223826797

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772ca92179c3634f3e31a80bbc272ed8022e3572 by Abseil Team <absl-team@google.com>:

Fix misspellings in absl::variant comments and replace a ' with a `.

PiperOrigin-RevId: 223807911

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35dcdc2fbf299d195658aac101887f6dcad1de2f by Abseil Team <absl-team@google.com>:

Bug fix in CMakeLists.txt file (SRCS --> HDRS).

The compressed_tuple header-only library is being defined
with the SRCS parameter instead of the HDRS parameter and
this has been observed to cause some builds on some platforms
to attempt to create a static library from it which fails
since there are no .cc sources.

PiperOrigin-RevId: 223805367

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4a57a3d2045bb137c0c97958e45ce425190b8d3e by Chris Kennelly <ckennelly@google.com>:

Add test that absl::make_unique value initializes memory.

PiperOrigin-RevId: 223801819

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dfe8289d7f4dcc6bb568a26aaf192a89e896bdfd by Chris Kennelly <ckennelly@google.com>:

SpinLock: Use exchange to avoid missing wakeups.

The default fast path for SpinLock::Unlock does not use an atomic.  If the
SpinLock becomes contended while we are unlocking between lockword_.load and
lockword_.store, we will fail to wake up the new waiter.  This can cause
unexpected latency spikes.

PiperOrigin-RevId: 223800369

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9b9d35df786482f0016f77dd31691eff81503d23 by Abseil Team <absl-team@google.com>:

Update absl/hash/CMakeLists.txt to use new functions
i.e. absl_cc_(library|test)

PiperOrigin-RevId: 223755819

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c2014e2704b87e7cdce2d2a0287c7e2397752296 by Abseil Team <absl-team@google.com>:

Update absl/debugging/CMakeLists.txt to use new functions
i.e. absl_cc_(library|test)

PiperOrigin-RevId: 223751986

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d83a4e09126400e3fd80645cb03ee558f532271e by Derek Mauro <dmauro@google.com>:

Cleanup synchronization benchmarks.

PiperOrigin-RevId: 223589416

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fad140b473586531b5b12843f942ec27dfcf5e93 by CJ Johnson <johnsoncj@google.com>:

Makes unifies the order of forward_iterator and input_iterator overloads

PiperOrigin-RevId: 223580660

--
6cd7c96faa7cc5f79f574e35a1b13837ef187d05 by Abseil Team <absl-team@google.com>:

Internal Change.

PiperOrigin-RevId: 223561629

--
bd2e545356b0f548af0e3c14bb2f7f0e712e49d0 by Shaindel Schwartz <shaindel@google.com>:

Remove misleading comments. try_emplace() does not exist for the hash_set containers.

PiperOrigin-RevId: 223543089

--
0cd380a53b587eb7aacc4003a4a3bbb6c78d7c10 by Derek Mauro <dmauro@google.com>:

Internal change

PiperOrigin-RevId: 223512551

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7156dfee599cb72e9adddfe0e6ae07a95ddf10bb by Greg Miller <jgm@google.com>:

Fixes UB that would result from constructing, multiplying, or dividing a
Duration with a double "NaN" value. This CL changes the absl::Duration
*implementation* to return an InfiniteDuration value that has the same sign as
the given NaN.

PiperOrigin-RevId: 223407499

--
196b7d18609958267951882baf7f9429e49bcafa by CJ Johnson <johnsoncj@google.com>:

Addresses NVCC+MSVC compilation bug where `inlined_capacity()` was not considered valid in constexpr

PiperOrigin-RevId: 223397718
GitOrigin-RevId: cd076f55c1fa600131f6dda392533dfe61679fc0
Change-Id: I5423ca6470f661a7c6f73aa8fee49990446f157f

absl/time/duration.cc

@@ -78,10 +78,16 @@ constexpr int64_t kint64min = std::numeric_limits<int64_t>::min();
 
 // Can't use std::isinfinite() because it doesn't exist on windows.
 inline bool IsFinite(double d) {
+  if (std::isnan(d)) return false;
   return d != std::numeric_limits<double>::infinity() &&
          d != -std::numeric_limits<double>::infinity();
 }
 
+inline bool IsValidDivisor(double d) {
+  if (std::isnan(d)) return false;
+  return d != 0.0;
+}
+
 // Can't use std::round() because it is only available in C++11.
 // Note that we ignore the possibility of floating-point over/underflow.
 template <typename Double>
@@ -455,7 +461,7 @@ Duration& Duration::operator/=(int64_t r) {
 }
 
 Duration& Duration::operator/=(double r) {
-  if (time_internal::IsInfiniteDuration(*this) || r == 0.0) {
+  if (time_internal::IsInfiniteDuration(*this) || !IsValidDivisor(r)) {
     const bool is_neg = (std::signbit(r) != 0) != (rep_hi_ < 0);
     return *this = is_neg ? -InfiniteDuration() : InfiniteDuration();
   }

absl/time/duration_test.cc

@@ -803,6 +803,40 @@ TEST(Duration, DivisionByZero) {
   EXPECT_EQ(-dbl_inf, absl::FDivDuration(-any_dur, zero));
 }
 
+TEST(Duration, NaN) {
+  // Note that IEEE 754 does not define the behavior of a nan's sign when it is
+  // copied, so the code below allows for either + or - InfiniteDuration.
+#define TEST_NAN_HANDLING(NAME, NAN)           \
+  do {                                         \
+    const auto inf = absl::InfiniteDuration(); \
+    auto x = NAME(NAN);                        \
+    EXPECT_TRUE(x == inf || x == -inf);        \
+    auto y = NAME(42);                         \
+    y *= NAN;                                  \
+    EXPECT_TRUE(y == inf || y == -inf);        \
+    auto z = NAME(42);                         \
+    z /= NAN;                                  \
+    EXPECT_TRUE(z == inf || z == -inf);        \
+  } while (0)
+
+  const double nan = std::numeric_limits<double>::quiet_NaN();
+  TEST_NAN_HANDLING(absl::Nanoseconds, nan);
+  TEST_NAN_HANDLING(absl::Microseconds, nan);
+  TEST_NAN_HANDLING(absl::Milliseconds, nan);
+  TEST_NAN_HANDLING(absl::Seconds, nan);
+  TEST_NAN_HANDLING(absl::Minutes, nan);
+  TEST_NAN_HANDLING(absl::Hours, nan);
+
+  TEST_NAN_HANDLING(absl::Nanoseconds, -nan);
+  TEST_NAN_HANDLING(absl::Microseconds, -nan);
+  TEST_NAN_HANDLING(absl::Milliseconds, -nan);
+  TEST_NAN_HANDLING(absl::Seconds, -nan);
+  TEST_NAN_HANDLING(absl::Minutes, -nan);
+  TEST_NAN_HANDLING(absl::Hours, -nan);
+
+#undef TEST_NAN_HANDLING
+}
+
 TEST(Duration, Range) {
   const absl::Duration range = ApproxYears(100 * 1e9);
   const absl::Duration range_future = range;

absl/time/time.h

@@ -69,6 +69,7 @@
 #include <winsock2.h>
 #endif
 #include <chrono>  // NOLINT(build/c++11)
+#include <cmath>
 #include <cstdint>
 #include <ctime>
 #include <ostream>
@@ -411,10 +412,12 @@ Duration Milliseconds(T n) {
 }
 template <typename T, time_internal::EnableIfFloat<T> = 0>
 Duration Seconds(T n) {
-  if (n >= 0) {
+  if (n >= 0) {  // Note: `NaN >= 0` is false.
     if (n >= (std::numeric_limits<int64_t>::max)()) return InfiniteDuration();
     return time_internal::MakePosDoubleDuration(n);
   } else {
+    if (std::isnan(n))
+      return std::signbit(n) ? -InfiniteDuration() : InfiniteDuration();
     if (n <= (std::numeric_limits<int64_t>::min)()) return -InfiniteDuration();
     return -time_internal::MakePosDoubleDuration(-n);
   }