[llvm-commits] [llvm] r82507 - in /llvm/trunk: include/llvm/Analysis/DebugInfo.h lib/Analysis/DebugInfo.cpp

[Daniel Dunbar]

Author: ddunbar
Date: Mon Sep 21 21:03:18 2009
New Revision: 82507

URL: http://llvm.org/viewvc/llvm-project?rev=82507&view=rev
Log:
Switch DIDescriptor to use a TrackingVH. - This makes it much safer to work with debug info, since it was extraordinarily easy to have dangling pointers thanks to MDNode uniquing.

Modified:
    llvm/trunk/include/llvm/Analysis/DebugInfo.h
    llvm/trunk/lib/Analysis/DebugInfo.cpp

Modified: llvm/trunk/include/llvm/Analysis/DebugInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/DebugInfo.h?rev=82507&r1=82506&r2=82507&view=diff

==============================================================================
--- llvm/trunk/include/llvm/Analysis/DebugInfo.h (original)
+++ llvm/trunk/include/llvm/Analysis/DebugInfo.h Mon Sep 21 21:03:18 2009
@@ -24,6 +24,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/Support/Dwarf.h"
+#include "llvm/Support/ValueHandle.h"
 
 namespace llvm {
   class BasicBlock;
@@ -45,7 +46,7 @@
 
   class DIDescriptor {
   protected:
-    MDNode *DbgNode;
+    TrackingVH<MDNode> DbgNode;
 
     /// DIDescriptor constructor.  If the specified node is non-null, check
     /// to make sure that the tag in the descriptor matches 'RequiredTag'.  If

Modified: llvm/trunk/lib/Analysis/DebugInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/DebugInfo.cpp?rev=82507&r1=82506&r2=82507&view=diff

==============================================================================
--- llvm/trunk/lib/Analysis/DebugInfo.cpp (original)
+++ llvm/trunk/lib/Analysis/DebugInfo.cpp Mon Sep 21 21:03:18 2009
@@ -267,8 +267,17 @@
     return;
 
   assert (!D.isNull() && "Can not replace with null");
-  DbgNode->replaceAllUsesWith(D.getNode());
-  delete DbgNode;
+
+  // Since we use a TrackingVH for the node, its easy for clients to manufacture
+  // legitimate situations where they want to replaceAllUsesWith() on something
+  // which, due to uniquing, has merged with the source. We shield clients from
+  // this detail by allowing a value to be replaced with replaceAllUsesWith()
+  // itself.
+  if (getNode() != D.getNode()) {
+    MDNode *Node = DbgNode;
+    Node->replaceAllUsesWith(D.getNode());
+    delete Node;
+  }
 }
 
 /// Verify - Verify that a compile unit is well formed.
@@ -395,7 +404,7 @@
 /// dump - Print descriptor.
 void DIDescriptor::dump() const {
   errs() << "[" << dwarf::TagString(getTag()) << "] ";
-  errs().write_hex((intptr_t)DbgNode) << ']';
+  errs().write_hex((intptr_t) &*DbgNode) << ']';
 }
 
 /// dump - Print compile unit.