Export of internal Abseil changes

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9c9eb300c95024ea4242bbb4835595f555cb1eed by Derek Mauro <dmauro@google.com>:

Sync string_view comments from the internal copy

PiperOrigin-RevId: 328582796

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c0bc4e77a46889430a1a40d836a5ff426a4a5bc9 by Xiaoyi Zhang <zhangxy@google.com>:

Make `absl::allocator_traits` an alias to `std::allocator_traits` for C++17 or
above. `std::allocator_traits` should have all its members since C++17 so we
don't need a backport.

PiperOrigin-RevId: 328258154

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5599a3c0f2d865128057b5e267a397011cd032d0 by Derek Mauro <dmauro@google.com>:

Fix an #endif comment

Reported at https://groups.google.com/g/abseil-io/c/GRUdB0bBrG8/m/852HrgchCQAJ

PiperOrigin-RevId: 328247093

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abd7e98088267f436e6c10779e574153ece015be by Abseil Team <absl-team@google.com>:

Don't call win32 APIs for UWP builds

symbolize.cc is including symbolize_win32.inc for all Windows builds,
including UWP builds. However, UWP doesn't have access to win32 APIs, so
it should instead include symbolize_unimplemented.inc.

This allows the necessary functions to still exist and be called, but
the win32 calls are not made.

This is part of the effort to enable Abseil in ANGLE:
https://anglebug.com/4873

PiperOrigin-RevId: 328226766

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f622d3dfb804a6f427c1fd86ee69f47785b49483 by Greg Falcon <gfalcon@google.com>:

Remove incorrect claims of HASH_NAMESPACE support in Abseil hash.

The documentation presently claims that absl::Hash will look for legacy hashers (e.g, in the __gnu_cxx namespace) as controlled by the HASH_NAMESPACE preprocessor define, but this has never been true.

(Vestigial support for this appears in the form `ABSL_INTERNAL_LEGACY_HASH_NAMESPACE`, but this is not a supported extension point, as indicated by the use of `INTERNAL` in the name.)

PiperOrigin-RevId: 328154123

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32b40a25efe1f7f7da98ce8faf3482c825464ed4 by Abseil Team <absl-team@google.com>:

Switch ABSL_INTERNAL_IGNORE_READS_ATTRIBUTE_ENABLED checks to defined().

PiperOrigin-RevId: 328151556
GitOrigin-RevId: 9c9eb300c95024ea4242bbb4835595f555cb1eed
Change-Id: Ib0686286f7889a976311e8cd2b35655765a8d033

1 files changed, 6 insertions, 0 deletions

diff --git a/absl/strings/string_view.h b/absl/strings/string_view.h
index 8a9db8c3..5260b5b7 100644
--- a/absl/strings/string_view.h
+++ b/absl/strings/string_view.h
@@ -111,6 +111,11 @@ ABSL_NAMESPACE_BEGIN
 // example, when splitting a string, `std::vector<absl::string_view>` is a
 // natural data type for the output.
 //
+// For another example, a Cord is a non-contiguous, potentially very
+// long string-like object.  The Cord class has an interface that iteratively
+// provides string_view objects that point to the successive pieces of a Cord
+// object.
+//
 // When constructed from a source which is NUL-terminated, the `string_view`
 // itself will not include the NUL-terminator unless a specific size (including
 // the NUL) is passed to the constructor. As a result, common idioms that work
@@ -382,6 +387,7 @@ 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`.
+  // Use absl::ClippedSubstr if you need a truncating substr operation.
   constexpr string_view substr(size_type pos, size_type n = npos) const {
     return ABSL_PREDICT_FALSE(pos > length_)
                ? (base_internal::ThrowStdOutOfRange(