Bug 29977 - dwarf-reader: Fix canonical DIE propagation canceling

When canceling canonical DIE propagation, we wrongly assume that the
pair of DIEs being compared yield a COMPARE_RESULT_UNKNOWN result.
The reality is that it can also yield a COMPARE_RESULT_DIFFERENT
result, especially when we are looking at the first sub-type that
compares different and that triggered the canonical DIE propagation
canceling to begin with.

This can be reproduced by the command:

$ fedabipkgdiff --self-compare -a --from fc37 xorg-x11-server-Xvfb

Fixed thus.

	* src/abg-dwarf-reader.cc
	(offset_pairs_stack_type::cancel_canonical_propagated_type): The
	result of comparing the canonical-propagated types being canceled
	is either COMPARISON_RESULT_UNKNOWN or
	COMPARISON_RESULT_DIFFERENT.  Also, do not forget to update the
	cached value for the comparison of the depend types too.

Signed-off-by: Dodji Seketeli <dodji@redhat.com>

diff --git a/src/abg-dwarf-reader.cc b/src/abg-dwarf-reader.cc
index 4fdd43909bdb7408cf1abd2515a0892c8f29094d..113dbdcb3591426f631494db272d32d6126b9c49 100644 (file)
--- a/src/abg-dwarf-reader.cc
+++ b/src/abg-dwarf-reader.cc
@@ -5702,12 +5702,23 @@ struct offset_pairs_stack_type
          }
        // Update the cached result.  We know the comparison result
        // must now be different.
-       auto comp_result_it = rdr_.die_comparison_results_.find(p);
+       auto comp_result_it = rdr_.die_comparison_results_.find(dependant_type);
        if (comp_result_it != rdr_.die_comparison_results_.end())
-         {
-           ABG_ASSERT(comp_result_it->second == COMPARISON_RESULT_UNKNOWN);
-           comp_result_it->second= COMPARISON_RESULT_DIFFERENT;
-         }
+         comp_result_it->second= COMPARISON_RESULT_DIFFERENT;
+      }
+
+    // Update the cached result of the root type to cancel too.
+    auto comp_result_it = rdr_.die_comparison_results_.find(p);
+    if (comp_result_it != rdr_.die_comparison_results_.end())
+      {
+       // At this point, the result of p is either
+       // COMPARISON_RESULT_UNKNOWN (if we cache comparison
+       // results of that kind) or COMPARISON_RESULT_DIFFERENT.
+       // Make sure it's the cached result is now
+       // COMPARISON_RESULT_DIFFERENT.
+       if (comp_result_it->second == COMPARISON_RESULT_UNKNOWN)
+         comp_result_it->second= COMPARISON_RESULT_DIFFERENT;
+       ABG_ASSERT(comp_result_it->second == COMPARISON_RESULT_DIFFERENT);
       }
 
     if (rdr_.propagated_types_.find(p) != rdr_.propagated_types_.end())