Export of internal Abseil changes.

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ed4be0cb9a708158187a0628c1c2167ae6783274 by Greg Falcon <gfalcon@google.com>:

Refactor a string unit test into a template function for internal purposes.

PiperOrigin-RevId: 210798880

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e4c734be903ac7b3a88caf4b17909343c283a21a by Abseil Team <absl-team@google.com>:

Add a note that the RFC3339_* format specifiers use %Y, and so
do not produce 4-digit years on output nor require 4-digit years
on input, as a strict reading of RFC3339 might require.

PiperOrigin-RevId: 210785544

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cfb5e32f9397e49ddb731445a191b36652fe2f6d by Greg Falcon <gfalcon@google.com>:

Refactor a string unit test into a template function for internal purposes.

PiperOrigin-RevId: 210776525

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105ee700e62869cfda2a37e6f7c2ea483f8fc75e by Xiaoyi Zhang <zhangxy@google.com>:

Correctly define ABSL_HAVE_STD_STRING_VIEW for MSVC 2017. Currently the macro
is not defined even though MSVC 2017 provides `std::string_view`, and this
means both `absl::string_view` and `std::string_view` exist as distinct types.
A bunch of places relying on the false assumption that
`string_view::const_iterator` is `const char*` have to be fixed to build
successfully.

See related github issue https://github.com/abseil/abseil-cpp/issues/161.

PiperOrigin-RevId: 210764947
GitOrigin-RevId: ed4be0cb9a708158187a0628c1c2167ae6783274
Change-Id: I7a9658b3201aa669db9d3d90474feb08072718c7

1 files changed, 6 insertions, 3 deletions

diff --git a/absl/strings/string_view_test.cc b/absl/strings/string_view_test.cc
index 30d5f00..217fda0 100644
--- a/absl/strings/string_view_test.cc
+++ b/absl/strings/string_view_test.cc
@@ -816,11 +816,14 @@ TEST(StringViewTest, FrontBackSingleChar) {
 // libc++, it doesn't allow `nullptr` in the constexpr context, with the error
 // "read of dereferenced null pointer is not allowed in a constant expression".
 // At run time, the behavior of `std::char_traits::length()` on `nullptr` is
-// undefined by the standard and usually results in crash with libc++. This
-// conforms to the standard, but `absl::string_view` implements a different
+// undefined by the standard and usually results in crash with libc++.
+// In MSVC, creating a constexpr string_view from nullptr also triggers an
+// "unevaluable pointer value" error. This compiler implementation conforms
+// to the standard, but `absl::string_view` implements a different
 // behavior for historical reasons. We work around tests that construct
 // `string_view` from `nullptr` when using libc++.
-#if !defined(ABSL_HAVE_STD_STRING_VIEW) || !defined(_LIBCPP_VERSION)
+#if !defined(ABSL_HAVE_STD_STRING_VIEW) || \
+    (!defined(_LIBCPP_VERSION) && !defined(_MSC_VER))
 #define ABSL_HAVE_STRING_VIEW_FROM_NULLPTR 1
 #endif  // !defined(ABSL_HAVE_STD_STRING_VIEW) || !defined(_LIBCPP_VERSION)