Defer the writing of the source position data to the relocation information...

src/objects.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4129 matching lines @@
 // source for this function is found.
 int Code::SourcePosition(Address pc) {
   int distance = kMaxInt;
   int position = kNoPosition;  // Initially no position found.
   // Run through all the relocation info to find the best matching source
   // position. All the code needs to be considered as the sequence of the
   // instructions in the code does not necessarily follow the same order as the
   // source.
   RelocIterator it(this, RelocInfo::kPositionMask);
   while (!it.done()) {
-    if (it.rinfo()->pc() < pc && (pc - it.rinfo()->pc()) < distance) {
-      position = it.rinfo()->data();
-      distance = pc - it.rinfo()->pc();
+    // Only look at positions after the current pc.
+    if (it.rinfo()->pc() < pc) {
+      // Get position and distance.
+      int dist = pc - it.rinfo()->pc();
+      int pos = it.rinfo()->data();
+      // If this position is closer than the current candidate or if it has the
+      // same distance as the current candidate and the position is higher then
+      // this position is the new candidate.
+      if ((dist < distance) ||
+          (dist == distance && pos > position)) {
+        position = pos;
+        distance = dist;
+      }
     }
     it.next();
   }
   return position;
 }
 
 
 // Same as Code::SourcePosition above except it only looks for statement
 // positions.
 int Code::SourceStatementPosition(Address pc) {
@@ skipping 2115 matching lines @@
   // No break point.
   if (break_point_objects()->IsUndefined()) return 0;
   // Single beak point.
   if (!break_point_objects()->IsFixedArray()) return 1;
   // Multiple break points.
   return FixedArray::cast(break_point_objects())->length();
 }
 
 
 } }  // namespace v8::internal