[libc++] random_device fails if open returns zero

random_device::random_device(const string&) wrongly assumes that open
can only validly return a file descriptor greater than zero.

This results in random_device believing that it didn't successfully open
the device causing it to throw in it's constructor, this ends up leaking
a file descriptor.

The fix is simple, don't error on file descriptors which are zero.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@210060 91177308-0d34-0410-b5e6-96231b3b80d8

test/numerics/rand/rand.device/ctor.pass.cpp

@@ -15,6 +15,7 @@
 
 #include <random>
 #include <cassert>
+#include <unistd.h>
 
 int main()
 {
@@ -29,6 +30,16 @@ int main()
     {
         std::random_device r;
     }
+    {
+        int ec;
+        ec = close(STDIN_FILENO);
+        assert(!ec);
+        ec = close(STDOUT_FILENO);
+        assert(!ec);
+        ec = close(STDERR_FILENO);
+        assert(!ec);
+        std::random_device r;
+    }
     {
         std::random_device r("/dev/urandom");;
     }