[PATCH] [asancov] Write coverage directly to a memory-mapped file

[Evgeniy Stepanov]

================
Comment at: lib/sanitizer_common/sanitizer_coverage.cc:120
@@ +119,3 @@
+
+void CoverageData::Extend(uptr npcs) {
+  if (!pc_fd) return;
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Kostya Serebryany wrote:
> this function deserves a comment. 
done

http://reviews.llvm.org/D3874