Export of internal Abseil changes.

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74c1330e29f1501f2738258faf9ec4564395c90a by Gennadiy Civil <misterg@google.com>:

Merging https://github.com/abseil/abseil-cpp/pull/166

PiperOrigin-RevId: 212487256

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4ac236574ff8fb3cc1125505292b0bd8c8192da9 by Abseil Team <absl-team@google.com>:

Allow c_move to take rvalue containers.

PiperOrigin-RevId: 212458618

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ce94e23984870db666d4c91623ae45b3c60b5b61 by Matt Armstrong <marmstrong@google.com>:

Internal change.

PiperOrigin-RevId: 212153041

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7d88d286821c5839934756dd63a704ed162c49cb by Chris Kennelly <ckennelly@google.com>:

Internal change

PiperOrigin-RevId: 211982309

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ddae814b3f609948c20551ea3d80bf51b973f480 by Abseil Team <absl-team@google.com>:

Remove unused argument from InlinedVector's AllocatorAndTag

This is not part of InlinedVector's public interface.

PiperOrigin-RevId: 211973017

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051fbfd81648a8da66c62c6603af63038d709c15 by Abseil Team <absl-team@google.com>:

Minor performance fix

PiperOrigin-RevId: 211820453

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c205cb2add7400bc8caf2131cb700eea560b7dbf by Laramie Leavitt <lar@google.com>:

Make absl::Span a tiny bit more consistent.

Add constexper to equivalent absl::Span members as described by
http://open-std.org/JTC1/SC22/WG21/docs/papers/2018/p0122r7.pdf

* Span constructor use consistently delegate to Span(ptr, length)
* Mark more member methods as constexpr.
* Use data() and size() consistently in member methods.

PiperOrigin-RevId: 211707244

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55500c9e941f2f58f4a95c121f32772408866eee by Derek Mauro <dmauro@google.com>:

Stop catching polymorphic exception types by value.
GCC 8 emits a warning for this.

PiperOrigin-RevId: 211684466
GitOrigin-RevId: 74c1330e29f1501f2738258faf9ec4564395c90a
Change-Id: Iceab4a5b30ee35d82ef494830262ad29c028cb0a

absl/types/span.h

@@ -379,64 +379,70 @@ class Span {
   //
   // Returns a reference to the i'th element of this span.
   constexpr reference at(size_type i) const {
-    return ABSL_PREDICT_TRUE(i < size())
-               ? ptr_[i]
+    return ABSL_PREDICT_TRUE(i < size())  //
+               ? *(data() + i)
                : (base_internal::ThrowStdOutOfRange(
                       "Span::at failed bounds check"),
-                  ptr_[i]);
+                  *(data() + i));
   }
 
   // Span::front()
   //
   // Returns a reference to the first element of this span.
-  reference front() const noexcept { return ABSL_ASSERT(size() > 0), ptr_[0]; }
+  constexpr reference front() const noexcept {
+    return ABSL_ASSERT(size() > 0), *data();
+  }
 
   // Span::back()
   //
   // Returns a reference to the last element of this span.
-  reference back() const noexcept {
-    return ABSL_ASSERT(size() > 0), ptr_[size() - 1];
+  constexpr reference back() const noexcept {
+    return ABSL_ASSERT(size() > 0), *(data() + size() - 1);
   }
 
   // Span::begin()
   //
   // Returns an iterator to the first element of this span.
-  constexpr iterator begin() const noexcept { return ptr_; }
+  constexpr iterator begin() const noexcept { return data(); }
 
   // Span::cbegin()
   //
   // Returns a const iterator to the first element of this span.
-  constexpr const_iterator cbegin() const noexcept { return ptr_; }
+  constexpr const_iterator cbegin() const noexcept { return begin(); }
 
   // Span::end()
   //
   // Returns an iterator to the last element of this span.
-  iterator end() const noexcept { return ptr_ + len_; }
+  constexpr iterator end() const noexcept { return data() + size(); }
 
   // Span::cend()
   //
   // Returns a const iterator to the last element of this span.
-  const_iterator cend() const noexcept { return end(); }
+  constexpr const_iterator cend() const noexcept { return end(); }
 
   // Span::rbegin()
   //
   // Returns a reverse iterator starting at the last element of this span.
-  reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
+  constexpr reverse_iterator rbegin() const noexcept {
+    return reverse_iterator(end());
+  }
 
   // Span::crbegin()
   //
   // Returns a reverse const iterator starting at the last element of this span.
-  const_reverse_iterator crbegin() const noexcept { return rbegin(); }
+  constexpr const_reverse_iterator crbegin() const noexcept { return rbegin(); }
 
   // Span::rend()
   //
   // Returns a reverse iterator starting at the first element of this span.
-  reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
+  constexpr reverse_iterator rend() const noexcept {
+    return reverse_iterator(begin());
+  }
 
   // Span::crend()
   //
   // Returns a reverse iterator starting at the first element of this span.
-  const_reverse_iterator crend() const noexcept { return rend(); }
+  constexpr const_reverse_iterator crend() const noexcept { return rend(); }
 
   // Span mutations
 
@@ -444,7 +450,7 @@ class Span {
   //
   // Removes the first `n` elements from the span.
   void remove_prefix(size_type n) noexcept {
-    assert(len_ >= n);
+    assert(size() >= n);
     ptr_ += n;
     len_ -= n;
   }
@@ -453,7 +459,7 @@ class Span {
   //
   // Removes the last `n` elements from the span.
   void remove_suffix(size_type n) noexcept {
-    assert(len_ >= n);
+    assert(size() >= n);
     len_ -= n;
   }
 
@@ -474,8 +480,8 @@ class Span {
   //   absl::MakeSpan(vec).subspan(4);     // {}
   //   absl::MakeSpan(vec).subspan(5);     // throws std::out_of_range
   constexpr Span subspan(size_type pos = 0, size_type len = npos) const {
-    return (pos <= len_)
-               ? Span(ptr_ + pos, span_internal::Min(len_ - pos, len))
+    return (pos <= size())
+               ? Span(data() + pos, span_internal::Min(size() - pos, len))
                : (base_internal::ThrowStdOutOfRange("pos > size()"), Span());
   }