C++: Fix taint-flow in preparation for frontend upgrade

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

@@ -94,8 +94,9 @@ predicate hasRawIndirectInstruction(Instruction instr, int indirectionIndex) {
 
 cached
 private newtype TDefOrUseImpl =
-  TDefImpl(Operand address, int indirectionIndex) {
-    exists(Instruction base | isDef(_, _, address, base, _, indirectionIndex) |
+  TDefImpl(BaseSourceVariableInstruction base, Operand address, int indirectionIndex) {
+    isDef(_, _, address, base, _, indirectionIndex) and
+    (
       // We only include the definition if the SSA pruning stage
       // concluded that the definition is live after the write.
       any(SsaInternals0::Def def).getAddressOperand() = address
@@ -105,8 +106,8 @@ private newtype TDefOrUseImpl =
       base.(VariableAddressInstruction).getAstVariable() instanceof GlobalLikeVariable
     )
   } or
-  TUseImpl(Operand operand, int indirectionIndex) {
-    isUse(_, operand, _, _, indirectionIndex) and
+  TUseImpl(BaseSourceVariableInstruction base, Operand operand, int indirectionIndex) {
+    isUse(_, operand, base, _, indirectionIndex) and
     not isDef(_, _, operand, _, _, _)
   } or
   TGlobalUse(GlobalLikeVariable v, IRFunction f, int indirectionIndex) {
@@ -193,7 +194,7 @@ abstract private class DefOrUseImpl extends TDefOrUseImpl {
 
   /**
    * Gets the instruction that computes the base of this definition or use.
-   * This is always a `VariableAddressInstruction` or an `AllocationInstruction`.
+   * This is always a `VariableAddressInstruction` or an `CallInstruction`.
    */
   abstract BaseSourceVariableInstruction getBase();
 
@@ -265,15 +266,17 @@ abstract class DefImpl extends DefOrUseImpl {
 }
 
 private class DirectDef extends DefImpl, TDefImpl {
-  DirectDef() { this = TDefImpl(address, ind) }
+  BaseSourceVariableInstruction base;
+
+  DirectDef() { this = TDefImpl(base, address, ind) }
 
-  override BaseSourceVariableInstruction getBase() { isDef(_, _, address, result, _, _) }
+  override BaseSourceVariableInstruction getBase() { result = base }
 
-  override int getIndirection() { isDef(_, _, address, _, result, ind) }
+  override int getIndirection() { isDef(_, _, address, base, result, ind) }
 
-  override Node0Impl getValue() { isDef(_, result, address, _, _, _) }
+  override Node0Impl getValue() { isDef(_, result, address, base, _, _) }
 
-  override predicate isCertain() { isDef(true, _, address, _, _, ind) }
+  override predicate isCertain() { isDef(true, _, address, base, _, ind) }
 }
 
 private class IteratorDef extends DefImpl, TIteratorDef {
@@ -316,57 +319,52 @@ abstract class UseImpl extends DefOrUseImpl {
 
 abstract private class OperandBasedUse extends UseImpl {
   Operand operand;
+  BaseSourceVariableInstruction base;
 
   bindingset[ind]
   OperandBasedUse() { any() }
 
   final override predicate hasIndexInBlock(IRBlock block, int index) {
     // See the comment in `ssa0`'s `OperandBasedUse` for an explanation of this
     // predicate's implementation.
-    exists(BaseSourceVariableInstruction base | base = this.getBase() |
-      if base.getAst() = any(Cpp::PostfixCrementOperation c).getOperand()
-      then
-        exists(Operand op, int indirectionIndex, int indirection |
-          indirectionIndex = this.getIndirectionIndex() and
-          indirection = this.getIndirection() and
-          op =
-            min(Operand cand, int i |
-              isUse(_, cand, base, indirection, indirectionIndex) and
-              block.getInstruction(i) = cand.getUse()
-            |
-              cand order by i
-            ) and
-          block.getInstruction(index) = op.getUse()
-        )
-      else operand.getUse() = block.getInstruction(index)
-    )
+    if base.getAst() = any(Cpp::PostfixCrementOperation c).getOperand()
+    then
+      exists(Operand op, int indirectionIndex, int indirection |
+        indirectionIndex = this.getIndirectionIndex() and
+        indirection = this.getIndirection() and
+        op =
+          min(Operand cand, int i |
+            isUse(_, cand, base, indirection, indirectionIndex) and
+            block.getInstruction(i) = cand.getUse()
+          |
+            cand order by i
+          ) and
+        block.getInstruction(index) = op.getUse()
+      )
+    else operand.getUse() = block.getInstruction(index)
   }
 
+  final override BaseSourceVariableInstruction getBase() { result = base }
+
   final Operand getOperand() { result = operand }
 
   final override Cpp::Location getLocation() { result = operand.getLocation() }
 }
 
 private class DirectUse extends OperandBasedUse, TUseImpl {
-  DirectUse() { this = TUseImpl(operand, ind) }
-
-  override int getIndirection() { isUse(_, operand, _, result, ind) }
+  DirectUse() { this = TUseImpl(base, operand, ind) }
 
-  override BaseSourceVariableInstruction getBase() { isUse(_, operand, result, _, ind) }
+  override int getIndirection() { isUse(_, operand, base, result, ind) }
 
-  override predicate isCertain() { isUse(true, operand, _, _, ind) }
+  override predicate isCertain() { isUse(true, operand, base, _, ind) }
 
   override Node getNode() { nodeHasOperand(result, operand, ind) }
 }
 
 private class IteratorUse extends OperandBasedUse, TIteratorUse {
-  BaseSourceVariableInstruction container;
-
-  IteratorUse() { this = TIteratorUse(operand, container, ind) }
+  IteratorUse() { this = TIteratorUse(operand, base, ind) }
 
-  override int getIndirection() { isIteratorUse(container, operand, result, ind) }
-
-  override BaseSourceVariableInstruction getBase() { result = container }
+  override int getIndirection() { isIteratorUse(base, operand, result, ind) }
 
   override predicate isCertain() { none() }
 

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

@@ -146,14 +146,6 @@ int countIndirectionsForCppType(LanguageType langType) {
   )
 }
 
-/**
- * A `CallInstruction` that calls an allocation function such
- * as `malloc` or `operator new`.
- */
-class AllocationInstruction extends CallInstruction {
-  AllocationInstruction() { this.getStaticCallTarget() instanceof Cpp::AllocationFunction }
-}
-
 private predicate isIndirectionType(Type t) { t instanceof Indirection }
 
 private predicate hasUnspecifiedBaseType(Indirection t, Type base) {
@@ -368,7 +360,7 @@ newtype TBaseSourceVariable =
   // Each IR variable gets its own source variable
   TBaseIRVariable(IRVariable var) or
   // Each allocation gets its own source variable
-  TBaseCallVariable(AllocationInstruction call)
+  TBaseCallVariable(CallInstruction call) { not call.getResultIRType() instanceof IRVoidType }
 
 abstract private class AbstractBaseSourceVariable extends TBaseSourceVariable {
   /** Gets a textual representation of this element. */
@@ -396,11 +388,11 @@ class BaseIRVariable extends AbstractBaseSourceVariable, TBaseIRVariable {
 }
 
 class BaseCallVariable extends AbstractBaseSourceVariable, TBaseCallVariable {
-  AllocationInstruction call;
+  CallInstruction call;
 
   BaseCallVariable() { this = TBaseCallVariable(call) }
 
-  AllocationInstruction getCallInstruction() { result = call }
+  CallInstruction getCallInstruction() { result = call }
 
   override string toString() { result = call.toString() }
 
@@ -504,8 +496,7 @@ private class BaseIRVariableInstruction extends BaseSourceVariableInstruction,
   override BaseIRVariable getBaseSourceVariable() { result.getIRVariable() = this.getIRVariable() }
 }
 
-private class BaseAllocationInstruction extends BaseSourceVariableInstruction, AllocationInstruction
-{
+private class BaseCallInstruction extends BaseSourceVariableInstruction, CallInstruction {
   override BaseCallVariable getBaseSourceVariable() { result.getCallInstruction() = this }
 }