[PATCH] PR20721: Don't let UBSan print inaccessible memory

[Evgeniy Stepanov]

================
Comment at: lib/sanitizer_common/sanitizer_posix_libcdep.cc:171
@@ +170,3 @@
+  int sock_pair[2];
+  if (pipe(sock_pair))
+    return false;
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Pipes have capacity, and large writes can block.
Maybe write to /dev/null instead?

http://reviews.llvm.org/D5253