[PATCH] D45645: Remove faulty assertion in llvm-pdbutil

[Adrian McCarthy via Phabricator via llvm-commits]

amccarth created this revision.
amccarth added a reviewer: zturner.
Herald added a subscriber: sanjoy.

If a class's first data member is an instance of an empty class, then an assertion in the `PrettyClassLayoutGraphicalDumper` would fail.  The storage is reserved, but it's not marked as in use.

As far as I understand, it's the assertion that's faulty, so I removed it and updated the nearby comment.  If you think the `MapUse` is computed wrong in this case, let me know and I'll investigate further.

Found by running llvm-pdbutil against its own PDB, and this assertion would fail on `HashAdjusters`, which is a HashTable whose first data member is a `TraitsT`, which is a `PdbHashTraits<T>`, which is an empty struct.  (The struct has a specialization for `uint32_t`, but that specialization doesn't apply here because the `T` is actually `ulittle32_t`.)


https://reviews.llvm.org/D45645

Files:
  llvm/tools/llvm-pdbutil/PrettyClassLayoutGraphicalDumper.cpp


Index: llvm/tools/llvm-pdbutil/PrettyClassLayoutGraphicalDumper.cpp
===================================================================
--- llvm/tools/llvm-pdbutil/PrettyClassLayoutGraphicalDumper.cpp
+++ llvm/tools/llvm-pdbutil/PrettyClassLayoutGraphicalDumper.cpp
@@ -50,12 +50,9 @@
     uint32_t RelativeOffset = Item->getOffsetInParent();
     CurrentAbsoluteOffset = ClassOffsetZero + RelativeOffset;
 
-    // Since there is storage there, it should be set!  However, this might
-    // be an empty base, in which case it could extend outside the bounds of
-    // the parent class.
+    // This might be an empty base, in which case it could extend outside the
+    // bounds of the parent class.
     if (RelativeOffset < UseMap.size() && (Item->getSize() > 0)) {
-      assert(UseMap.test(RelativeOffset));
-
       // If there is any remaining padding in this class, and the offset of the
       // new item is after the padding, then we must have just jumped over some
       // padding.  Print a padding row and then look for where the next block


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