Export of internal Abseil changes

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09c1e7877210fe85c43631538303af801c233e89 by Gennadiy Rozental <rogeeff@google.com>:

Change CordRep::length to size_t to be compatible with ChunkIterator.

PiperOrigin-RevId: 297901255

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226d5e79fb4e20fb09d75f034624d5be770f4ece by Derek Mauro <dmauro@google.com>:

Makes absl::string_view::substr constexpr for std::string_view compatibility
Fixes #627

PiperOrigin-RevId: 297872778

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851aa24a22d0ba5552098bf7e5735c95e4a8d4f7 by Abseil Team <absl-team@google.com>:

Reformat one line.

PiperOrigin-RevId: 297839574

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4f449c462583797455375fa6f1365a6b2cfa7e0a by Benjamin Barenblat <bbaren@google.com>:

Internal change

PiperOrigin-RevId: 297677173

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2d41a250e9a8f272946bc3262463e4025d88fba3 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 297537076

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6e7fbe1e90999a58556d41955bef44033c61876c by Gennadiy Rozental <rogeeff@google.com>:

Internal change

PiperOrigin-RevId: 297376994

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5acf79338191b31cec158b06cd96ca8dfa3e81fe by Derek Mauro <dmauro@google.com>:

Add a debug-mode bounds-check on absl::Span::operator[].

PiperOrigin-RevId: 297355826

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1c540d06a56c7e92bb07b90f16b4e00b014ef18f by CJ Johnson <johnsoncj@google.com>:

Adding new LTS to the list

PiperOrigin-RevId: 297235265

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696ce48bea6927436ff89f59b887e5869b1b0f38 by Derek Mauro <dmauro@google.com>:

Fix build on FreeBSD/powerpc (implement UnscaledCycleClock)

Merges/Fixes GitHub #616

PiperOrigin-RevId: 297188640
GitOrigin-RevId: 09c1e7877210fe85c43631538303af801c233e89
Change-Id: I5d97b16bb6378792d2fcf7d29080cca18aa7729a

7 files changed, 23 insertions, 12 deletions

diff --git a/absl/strings/cord.cc b/absl/strings/cord.cc
index d9503ae332d7..5cc68539941d 100644
--- a/absl/strings/cord.cc
+++ b/absl/strings/cord.cc
@@ -136,8 +136,6 @@ inline const CordRepExternal* CordRep::external() const {
 
 static const size_t kFlatOverhead = offsetof(CordRep, data);
 
-static_assert(kFlatOverhead == 13, "Unittests assume kFlatOverhead == 13");
-
 // Largest and smallest flat node lengths we are willing to allocate
 // Flat allocation size is stored in tag, which currently can encode sizes up
 // to 4K, encoded as multiple of either 8 or 32 bytes.
diff --git a/absl/strings/internal/cord_internal.h b/absl/strings/internal/cord_internal.h
index 5b5d10830891..830ceaf473bd 100644
--- a/absl/strings/internal/cord_internal.h
+++ b/absl/strings/internal/cord_internal.h
@@ -86,8 +86,7 @@ struct CordRepExternal;
 struct CordRep {
   // The following three fields have to be less than 32 bytes since
   // that is the smallest supported flat node size.
-  // We use uint64_t for the length even in 32-bit binaries.
-  uint64_t length;
+  size_t length;
   Refcount refcount;
   // If tag < FLAT, it represents CordRepKind and indicates the type of node.
   // Otherwise, the node type is CordRepFlat and the tag is the encoded size.
diff --git a/absl/strings/internal/str_split_internal.h b/absl/strings/internal/str_split_internal.h
index b54f6ebe09e0..6f5bc095fbbe 100644
--- a/absl/strings/internal/str_split_internal.h
+++ b/absl/strings/internal/str_split_internal.h
@@ -65,8 +65,8 @@ class ConvertibleToStringView {
       : value_(s) {}
 
   // Matches rvalue strings and moves their data to a member.
-ConvertibleToStringView(std::string&& s)  // NOLINT(runtime/explicit)
-    : copy_(std::move(s)), value_(copy_) {}
+  ConvertibleToStringView(std::string&& s)  // NOLINT(runtime/explicit)
+      : copy_(std::move(s)), value_(copy_) {}
 
   ConvertibleToStringView(const ConvertibleToStringView& other)
       : copy_(other.copy_),
diff --git a/absl/strings/string_view.h b/absl/strings/string_view.h
index 1861ea62a9ea..55e80d62ae80 100644
--- a/absl/strings/string_view.h
+++ b/absl/strings/string_view.h
@@ -382,11 +382,12 @@ class string_view {
   // Returns a "substring" of the `string_view` (at offset `pos` and length
   // `n`) as another string_view. This function throws `std::out_of_bounds` if
   // `pos > size`.
-  string_view substr(size_type pos, size_type n = npos) const {
-    if (ABSL_PREDICT_FALSE(pos > length_))
-      base_internal::ThrowStdOutOfRange("absl::string_view::substr");
-    n = (std::min)(n, length_ - pos);
-    return string_view(ptr_ + pos, n);
+  constexpr string_view substr(size_type pos, size_type n = npos) const {
+    return ABSL_PREDICT_FALSE(pos > length_)
+               ? (base_internal::ThrowStdOutOfRange(
+                      "absl::string_view::substr"),
+                  string_view())
+               : string_view(ptr_ + pos, Min(n, length_ - pos));
   }
 
   // string_view::compare()
diff --git a/absl/strings/string_view_test.cc b/absl/strings/string_view_test.cc
index 7b1d56fac762..cb6a758fea6f 100644
--- a/absl/strings/string_view_test.cc
+++ b/absl/strings/string_view_test.cc
@@ -1086,6 +1086,14 @@ TEST(StringViewTest, ConstexprCompiles) {
   EXPECT_EQ(sp_npos, -1);
 }
 
+TEST(StringViewTest, ConstexprSubstr) {
+  constexpr absl::string_view foobar("foobar", 6);
+  constexpr absl::string_view foo = foobar.substr(0, 3);
+  constexpr absl::string_view bar = foobar.substr(3);
+  EXPECT_EQ(foo, "foo");
+  EXPECT_EQ(bar, "bar");
+}
+
 TEST(StringViewTest, Noexcept) {
   EXPECT_TRUE((std::is_nothrow_constructible<absl::string_view,
                                              const std::string&>::value));
diff --git a/absl/types/span.h b/absl/types/span.h
index 3283145a56b4..25347c63fe8c 100644
--- a/absl/types/span.h
+++ b/absl/types/span.h
@@ -276,7 +276,7 @@ class Span {
   // Returns a reference to the i'th element of this span.
   constexpr reference operator[](size_type i) const noexcept {
     // MSVC 2015 accepts this as constexpr, but not ptr_[i]
-    return *(data() + i);
+    return ABSL_ASSERT(i < size()), *(data() + i);
   }
 
   // Span::at()
diff --git a/absl/types/span_test.cc b/absl/types/span_test.cc
index 22467a0a767e..6ac234d365ad 100644
--- a/absl/types/span_test.cc
+++ b/absl/types/span_test.cc
@@ -232,6 +232,11 @@ TEST(IntSpan, ElementAccess) {
 
   EXPECT_EQ(s.front(), s[0]);
   EXPECT_EQ(s.back(), s[9]);
+
+#ifndef NDEBUG
+  EXPECT_DEATH_IF_SUPPORTED(s[-1], "");
+  EXPECT_DEATH_IF_SUPPORTED(s[10], "");
+#endif
 }
 
 TEST(IntSpan, AtThrows) {