[PATCH] D52242: [sanitizer] Destroy and close a range's vmar if all its memory was unmapped

[Roland McGrath via Phabricator via llvm-commits]

mcgrathr added inline comments.


================
Comment at: lib/sanitizer_common/sanitizer_fuchsia.cc:283
+    if (size == size_) {
+      // Unmap the whole mapping by destroying and closing the vmar.
+      _zx_vmar_destroy(vmar);
----------------
This comment is a little ambiguous or misleading.
Destroying the VMAR is what unmaps the whole range.
Closing the VMAR handle just releases a now-useless resource; it has no effect itself on the state of mappings.


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Comment at: lib/sanitizer_common/sanitizer_fuchsia.cc:290
+    } else {
+      base_ = reinterpret_cast<void*>(addr + size);
+    }
----------------
This seems questionable and at least needs comments.
By moving base_ up you are telling the local bookkeeping that the reservation starts at the new base.
But the actual VMAR still exists and will always cover the full range set at its creation.
So the address space between the old base_ and the new base_ is still reserved, but you've lost track of it.



Repository:
  rCRT Compiler Runtime

https://reviews.llvm.org/D52242