[libstdc++] Add missing _M_try_acquire() to __platform_semaphore

libstdc++-v3/ChangeLog:
	* include/bits/semaphore_base.h: Add missing _M_try_acquire()
	member to __platform_wait.

(cherry picked from commit 5445da1a94bb4df752209e54f4aa21702609a20a)

diff --git a/libstdc++-v3/include/bits/semaphore_base.h b/libstdc++-v3/include/bits/semaphore_base.h
index 7e3235d182e9954dd3366bf378fe8ac7a42b56d0..35469e443b0e90c511faaac7c9e5767f16c5e59e 100644 (file)
--- a/libstdc++-v3/include/bits/semaphore_base.h
+++ b/libstdc++-v3/include/bits/semaphore_base.h
@@ -86,6 +86,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        }
     }
 
+    _GLIBCXX_ALWAYS_INLINE bool
+    _M_try_acquire() noexcept
+    {
+      for (;;)
+       {
+         auto __err = sem_trywait(&_M_semaphore);
+         if (__err && (errno == EINTR))
+           continue;
+         else if (__err && (errno == EAGAIN))
+           return false;
+         else if (__err)
+           std::terminate();
+         else
+           break;
+       }
+      return true;
+    }
+
     _GLIBCXX_ALWAYS_INLINE void
     _M_release(std::ptrdiff_t __update) noexcept
     {