Update libc++ to 8d23b742 (11 Jan 2022).

Notable changes:
* implement in_out_result in ranges
* implement uninitialized_copy{,_n} and uninitialized_move{,_n} in ranges
* use _LIBCPP_DEBUG_ASSERT in list
* alphabetize header includes.
* use Fuchsia-native monotonic clock for std::chrono::steady_clock
* properly handle specializations of std::is_placeholder
* add __cpo namespace to ranges::{advance, next, prev} for ADL reasons
* add template lerp function

ref:1cc313d57e8757bed1d0950624d0c3a2b7da8a4f

1 files changed, 19 insertions, 4 deletions

diff --git a/contrib/libs/cxxsupp/libcxx/src/chrono.cpp b/contrib/libs/cxxsupp/libcxx/src/chrono.cpp
index 5aa7af75894..4f2d51042ff 100644
--- a/contrib/libs/cxxsupp/libcxx/src/chrono.cpp
+++ b/contrib/libs/cxxsupp/libcxx/src/chrono.cpp
@@ -44,6 +44,10 @@
 #  endif
 #endif // defined(_LIBCPP_WIN32API)
 
+#if defined(__Fuchsia__)
+#  include <zircon/syscalls.h>
+#endif
+
 #if __has_include(<mach/mach_time.h>)
 # include <mach/mach_time.h>
 #endif
@@ -266,7 +270,18 @@ static steady_clock::time_point __libcpp_steady_clock_now() {
   return steady_clock::time_point(seconds(ts.tv_sec) + nanoseconds(ts.tv_nsec));
 }
 
-#elif defined(CLOCK_MONOTONIC)
+#  elif defined(__Fuchsia__)
+
+static steady_clock::time_point __libcpp_steady_clock_now() noexcept {
+  // Implicitly link against the vDSO system call ABI without
+  // requiring the final link to specify -lzircon explicitly when
+  // statically linking libc++.
+#    pragma comment(lib, "zircon")
+
+  return steady_clock::time_point(nanoseconds(_zx_clock_get_monotonic()));
+}
+
+#  elif defined(CLOCK_MONOTONIC)
 
 static steady_clock::time_point __libcpp_steady_clock_now() {
     struct timespec tp;
@@ -275,9 +290,9 @@ static steady_clock::time_point __libcpp_steady_clock_now() {
     return steady_clock::time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec));
 }
 
-#else
-#   error "Monotonic clock not implemented on this platform"
-#endif
+#  else
+#    error "Monotonic clock not implemented on this platform"
+#  endif
 
 const bool steady_clock::is_steady;