C++: Remove a DefinitionExt reference.

Author: aschackmull

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowUtil.qll

@@ -1371,7 +1371,7 @@ class UninitializedNode extends Node {
   LocalVariable v;
 
   UninitializedNode() {
-    exists(Ssa::DefinitionExt def, Ssa::SourceVariable sv |
+    exists(Ssa::Definition def, Ssa::SourceVariable sv |
       def.getIndirectionIndex() = 0 and
       def.getValue().asInstruction() instanceof UninitializedInstruction and
       Ssa::defToNode(this, def, sv, _, _, _) and

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaInternals.qll

@@ -698,9 +698,9 @@ predicate outNodeHasAddressAndIndex(
  * Holds if `node` is the node that corresponds to the definition of `def`.
  */
 predicate defToNode(
-  Node node, DefinitionExt def, SourceVariable sv, IRBlock bb, int i, boolean uncertain
+  Node node, Definition def, SourceVariable sv, IRBlock bb, int i, boolean uncertain
 ) {
-  def.definesAt(sv, bb, i, _) and
+  def.definesAt(sv, bb, i) and
   (
     nodeHasOperand(node, def.getValue().asOperand(), def.getIndirectionIndex())
     or
@@ -1132,6 +1132,26 @@ class PhiNode extends SsaImpl::DefinitionExt {
   final DefinitionExt getAnInput() { this.hasInputFromBlock(result, _, _, _, _) }
 }
 
+/** An static single assignment (SSA) definition. */
+class Definition extends SsaImpl::Definition {
+  /**
+   * INTERNAL: Do not use.
+   */
+  Node0Impl getValue() { result = getDefImpl(this).getValue() }
+
+  /** Gets the indirection index of this definition. */
+  int getIndirectionIndex() { result = getDefImpl(this).getIndirectionIndex() }
+
+  /** Gets the indirection of this definition. */
+  int getIndirection() { result = getDefImpl(this).getIndirection() }
+
+  /**
+   * Holds if this definition is guaranteed to totally overwrite the buffer
+   * being written to.
+   */
+  predicate isCertain() { getDefImpl(this).isCertain() }
+}
+
 /** An static single assignment (SSA) definition. */
 class DefinitionExt extends SsaImpl::DefinitionExt {
   private DefinitionExt getAPhiInputOrPriorDefinition() { result = this.(PhiNode).getAnInput() }