C++: Fix comment and prevent false positives on chiOnlyPartiallyUpdatesLocation when Alias::getEndBitOffset doesn't have known value.

MathiasVP · MathiasVP · commit c86fc223b938 · 2021-03-05T08:53:24.000+01:00
diff --git a/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasedSSA.qll b/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasedSSA.qll
@@ -629,7 +629,11 @@ MemoryLocation getOperandMemoryLocation(MemoryOperand operand) {
 }
 
 /** Gets the start bit offset of a `MemoryLocation`, if any. */
-int getStartBitOffset(VariableMemoryLocation location) { result = location.getStartBitOffset() }
+int getStartBitOffset(VariableMemoryLocation location) {
+  result = location.getStartBitOffset() and Ints::hasValue(result)
+}
 
 /** Gets the end bit offset of a `MemoryLocation`, if any. */
-int getEndBitOffset(VariableMemoryLocation location) { result = location.getEndBitOffset() }
+int getEndBitOffset(VariableMemoryLocation location) {
+  result = location.getEndBitOffset() and Ints::hasValue(result)
+}
diff --git a/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstruction.qll b/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstruction.qll
@@ -179,9 +179,9 @@ private module Cached {
   }
 
   /**
-   * Holds if the `ChiPartialOperand` totally, but not exactly, overlaps with the `ChiTotalOperand`.
-   * This means that the `ChiPartialOperand` will not override the entire memory associated with the
-   * `ChiTotalOperand`.
+   * Holds if the `ChiPartialOperand` only partially overlaps with the `ChiTotalOperand`.
+   * This means that the `ChiPartialOperand` will not override the entire memory associated
+   * with the `ChiTotalOperand`.
    */
   cached
   predicate chiOnlyPartiallyUpdatesLocation(ChiInstruction chi) {
diff --git a/cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/SSAConstruction.qll b/cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/SSAConstruction.qll
@@ -179,9 +179,9 @@ private module Cached {
   }
 
   /**
-   * Holds if the `ChiPartialOperand` totally, but not exactly, overlaps with the `ChiTotalOperand`.
-   * This means that the `ChiPartialOperand` will not override the entire memory associated with the
-   * `ChiTotalOperand`.
+   * Holds if the `ChiPartialOperand` only partially overlaps with the `ChiTotalOperand`.
+   * This means that the `ChiPartialOperand` will not override the entire memory associated
+   * with the `ChiTotalOperand`.
    */
   cached
   predicate chiOnlyPartiallyUpdatesLocation(ChiInstruction chi) {
diff --git a/csharp/ql/src/experimental/ir/implementation/unaliased_ssa/internal/SSAConstruction.qll b/csharp/ql/src/experimental/ir/implementation/unaliased_ssa/internal/SSAConstruction.qll
@@ -179,9 +179,9 @@ private module Cached {
   }
 
   /**
-   * Holds if the `ChiPartialOperand` totally, but not exactly, overlaps with the `ChiTotalOperand`.
-   * This means that the `ChiPartialOperand` will not override the entire memory associated with the
-   * `ChiTotalOperand`.
+   * Holds if the `ChiPartialOperand` only partially overlaps with the `ChiTotalOperand`.
+   * This means that the `ChiPartialOperand` will not override the entire memory associated
+   * with the `ChiTotalOperand`.
    */
   cached
   predicate chiOnlyPartiallyUpdatesLocation(ChiInstruction chi) {
