First implementation of Rule-0-0-2, invariant conditions.

change_notes/2025-12-17-unfeasible-statement-refactor.md

@@ -0,0 +1,2 @@
+- `M0-1-2` - `InfeasiblePath.ql`:
+  - Refactored to share logic with `RULE-0-0-2` while allowing for different exceptional cases. No change in behavior expected.

cpp/autosar/src/rules/M0-1-2/InfeasiblePath.ql

@@ -16,22 +16,7 @@
 
 import cpp
 import codingstandards.cpp.autosar
-import semmle.code.cpp.rangeanalysis.SimpleRangeAnalysis
-import codingstandards.cpp.deadcode.UnreachableCode
-import semmle.code.cpp.controlflow.Guards
-
-/**
- * A "conditional" node in the control flow graph, i.e. one that can potentially have a true and false path.
- */
-class ConditionalControlFlowNode extends ControlFlowNode {
-  ConditionalControlFlowNode() {
-    // A conditional node is one with at least one of a true or false successor
-    (exists(getATrueSuccessor()) or exists(getAFalseSuccessor())) and
-    // Ignore conditions affected by macros, as they may include deliberate infeasible paths, or
-    // paths which are only feasible in certain macro expansions
-    not isAffectedByMacro()
-  }
-}
+import codingstandards.cpp.rules.invariantcondition.InvariantCondition
 
 /**
  * A `Loop` that contains a `break` statement.
@@ -40,132 +25,21 @@ class BreakingLoop extends Loop {
   BreakingLoop() { exists(BreakStmt break | this = break.getBreakable()) }
 }
 
-/**
- * Holds if the `ConditionalNode` has an infeasible `path` according to the control flow graph library.
- */
-predicate hasCFGDeducedInfeasiblePath(
-  ConditionalControlFlowNode cond, boolean infeasiblePath, string explanation
-) {
-  not cond.isFromTemplateInstantiation(_) and
-  // No true successor, so the true path has already been deduced as infeasible
-  not exists(cond.getATrueSuccessor()) and
-  infeasiblePath = true and
-  explanation = "this expression consists of constants which evaluate to false"
-  or
-  // No false successor, so false path has already been deduced as infeasible
-  not exists(cond.getAFalseSuccessor()) and
-  not cond.getEnclosingStmt() instanceof BreakingLoop and
-  infeasiblePath = false and
-  explanation = "this expression consists of constants which evaluate to true"
-}
-
-predicate isConstantRelationalOperation(
-  RelationalOperation rel, boolean infeasiblePath, string explanation
-) {
-  /*
-   * This predicate identifies a number of a cases where we can conclusive determine that a relational
-   * operation will always return true or false, based on the ranges for each operand as determined
-   * by the SimpleRangeAnalysis library (and any extensions provide in the Coding Standards library).
-   *
-   * Important note: in order to deduce that an relational operation _always_ returns true or false,
-   * we must ensure that it returns true or false for _all_ possible values of the operands. For
-   * example, it may be tempting to look at this relational operation on these ranges:
-   * ```
-   *   [0..5] < [0..10]
-   * ```
-   * And say that ub(lesser) < ub(greater) and therefore it is `true`, however this is not the case
-   * for all permutations (e.g. 5 < 0).
-   *
-   * Instead, we look at all four permutations of these two dimensions:
-   *  - Equal-to or not equal-to
-   *  - Always true or always false
-   */
+module AutosarConfig implements InvariantConditionConfigSig {
+  Query getQuery() { result = DeadCodePackage::infeasiblePathQuery() }
 
-  // This restricts the comparison to occur directly within the conditional node
-  // In theory we could also extend this to identify comparisons where the result is stored, then
-  // later read in a conditional control flow node within the same function (using SSA)
-  // Doing so would benefit from path explanations, but would require a more complex analysis
-  rel instanceof ConditionalControlFlowNode and
-  // If at least one operand includes an access of a volatile variable, the range analysis library may
-  // provide inaccurate results, so we ignore this case
-  not rel.getAnOperand().getAChild*().(VariableAccess).getTarget().isVolatile() and
-  exists(boolean isEqual |
-    if
-      rel instanceof GEExpr
-      or
-      rel instanceof LEExpr
-    then isEqual = true
-    else isEqual = false
-  |
-    // Not equal-to/always true
-    // If the largest value of the lesser operand is less than the smallest value of the greater
-    // operand, then the LT/GT comparison is always true
-    // Example: [0..5] < [6..10]
-    upperBound(rel.getLesserOperand()) < lowerBound(rel.getGreaterOperand()) and
-    explanation =
-      rel.getLesserOperand() + " (max value: " + upperBound(rel.getLesserOperand()) +
-        ") is always less than " + rel.getGreaterOperand() + " (minimum value: " +
-        lowerBound(rel.getGreaterOperand()) + ")" and
-    isEqual = false and
-    infeasiblePath = false
-    or
-    // Equal-to/always true
-    // If the largest value of the lesser operand is less than or equal to the smallest value of the
-    // greater operand, then the LTE/GTE comparison is always true
-    // Example: [0..6] <= [6..10]
-    upperBound(rel.getLesserOperand()) <= lowerBound(rel.getGreaterOperand()) and
-    explanation =
-      rel.getLesserOperand() + " (max value: " + upperBound(rel.getLesserOperand()) +
-        ") is always less than or equal to " + rel.getGreaterOperand() + " (minimum value: " +
-        lowerBound(rel.getGreaterOperand()) + ")" and
-    isEqual = true and
-    infeasiblePath = false
-    or
-    // Equal to/always false
-    // If the largest value of the greater operand is less than the smallest value of the lesser
-    // operand, then the LTE/GTE comparison is always false
-    // Example: [6..10] <= [0..5]
-    upperBound(rel.getGreaterOperand()) < lowerBound(rel.getLesserOperand()) and
-    explanation =
-      rel.getGreaterOperand() + " (max value: " + upperBound(rel.getGreaterOperand()) +
-        ") is always less than " + rel.getLesserOperand() + " (minimum value: " +
-        lowerBound(rel.getLesserOperand()) + ")" and
-    isEqual = true and
-    infeasiblePath = true
+  predicate isException(ControlFlowNode node) {
+    node.getEnclosingElement() instanceof BreakingLoop and
+    exists(node.getATrueSuccessor())
     or
-    // Equal to/always true
-    // If the largest value of the greater operand is less than or equal to the smallest value of the
-    // lesser operand, then the LT/GT comparison is always false
-    // Example: [6..10] < [0..6]
-    upperBound(rel.getGreaterOperand()) <= lowerBound(rel.getLesserOperand()) and
-    explanation =
-      rel.getGreaterOperand() + " (max value: " + upperBound(rel.getGreaterOperand()) +
-        ") is always less than or equal to " + rel.getLesserOperand() + " (minimum value: " +
-        lowerBound(rel.getLesserOperand()) + ")" and
-    isEqual = false and
-    infeasiblePath = true
-  )
-}
-
-/**
- * Holds if the `ConditionalNode` has an infeasible `path` for the reason given in `explanation`.
- */
-predicate hasInfeasiblePath(ConditionalControlFlowNode node, string message) {
-  exists(boolean infeasiblePath, string explanation |
-    not node.isFromTemplateInstantiation(_) and
-    if node.isFromUninstantiatedTemplate(_)
-    then message = "The path is unreachable in a template."
-    else message = "The " + infeasiblePath + " path is infeasible because " + explanation + "."
-  |
-    hasCFGDeducedInfeasiblePath(node, infeasiblePath, explanation) and
-    not isConstantRelationalOperation(node, infeasiblePath, _)
+    // Ignore conditions affected by macros, as they may include deliberate infeasible paths, or
+    // paths which are only feasible in certain macro expansions
+    node.isAffectedByMacro()
     or
-    isConstantRelationalOperation(node, infeasiblePath, explanation)
-  )
+    // Only consider reachability in uninstantiated templates, to avoid false positives
+    node.isFromTemplateInstantiation(_)
+  }
 }
 
-from ConditionalControlFlowNode cond, string explanation
-where
-  not isExcluded(cond, DeadCodePackage::infeasiblePathQuery()) and
-  hasInfeasiblePath(cond, explanation)
-select cond, explanation
+// Import the problems query predicate
+import InvariantCondition<AutosarConfig>

cpp/common/src/codingstandards/cpp/Literals.qll

@@ -69,6 +69,10 @@ class BoolLiteral extends Literal {
     or
     this.getValue() = "0" and this.getValueText() = "false"
   }
+
+  predicate isTrue() { this.getValue() = "1" }
+
+  predicate isFalse() { this.getValue() = "0" }
 }
 
 /**

cpp/common/src/codingstandards/cpp/exclusions/cpp/DeadCode4.qll

@@ -0,0 +1,26 @@
+//** THIS FILE IS AUTOGENERATED, DO NOT MODIFY DIRECTLY.  **/
+import cpp
+import RuleMetadata
+import codingstandards.cpp.exclusions.RuleMetadata
+
+newtype DeadCode4Query = TInvariantConditionQuery()
+
+predicate isDeadCode4QueryMetadata(Query query, string queryId, string ruleId, string category) {
+  query =
+    // `Query` instance for the `invariantCondition` query
+    DeadCode4Package::invariantConditionQuery() and
+  queryId =
+    // `@id` for the `invariantCondition` query
+    "cpp/misra/invariant-condition" and
+  ruleId = "RULE-0-0-2" and
+  category = "advisory"
+}
+
+module DeadCode4Package {
+  Query invariantConditionQuery() {
+    //autogenerate `Query` type
+    result =
+      // `Query` type for `invariantCondition` query
+      TQueryCPP(TDeadCode4PackageQuery(TInvariantConditionQuery()))
+  }
+}

cpp/common/src/codingstandards/cpp/exclusions/cpp/RuleMetadata.qll

@@ -16,6 +16,7 @@ import Const
 import Conversions
 import Conversions2
 import DeadCode
+import DeadCode4
 import Declarations
 import ExceptionSafety
 import Exceptions1
@@ -78,6 +79,7 @@ newtype TCPPQuery =
   TConversionsPackageQuery(ConversionsQuery q) or
   TConversions2PackageQuery(Conversions2Query q) or
   TDeadCodePackageQuery(DeadCodeQuery q) or
+  TDeadCode4PackageQuery(DeadCode4Query q) or
   TDeclarationsPackageQuery(DeclarationsQuery q) or
   TExceptionSafetyPackageQuery(ExceptionSafetyQuery q) or
   TExceptions1PackageQuery(Exceptions1Query q) or
@@ -140,6 +142,7 @@ predicate isQueryMetadata(Query query, string queryId, string ruleId, string cat
   isConversionsQueryMetadata(query, queryId, ruleId, category) or
   isConversions2QueryMetadata(query, queryId, ruleId, category) or
   isDeadCodeQueryMetadata(query, queryId, ruleId, category) or
+  isDeadCode4QueryMetadata(query, queryId, ruleId, category) or
   isDeclarationsQueryMetadata(query, queryId, ruleId, category) or
   isExceptionSafetyQueryMetadata(query, queryId, ruleId, category) or
   isExceptions1QueryMetadata(query, queryId, ruleId, category) or

cpp/common/src/codingstandards/cpp/rules/invariantcondition/InvariantCondition.qll

@@ -0,0 +1,159 @@
+/**
+ * Provides a library which includes a `problems` predicate for reporting
+ * invariant/infeasible code paths.
+ */
+
+import cpp
+import codingstandards.cpp.Customizations
+import codingstandards.cpp.Exclusions
+import semmle.code.cpp.rangeanalysis.SimpleRangeAnalysis
+import codingstandards.cpp.deadcode.UnreachableCode
+import semmle.code.cpp.controlflow.Guards
+
+signature module InvariantConditionConfigSig {
+  Query getQuery();
+
+  predicate isException(ControlFlowNode element);
+}
+
+private module Impl {
+  /**
+   * A "conditional" node in the control flow graph, i.e. one that can potentially have a true and false path.
+   */
+  class ConditionalControlFlowNode extends ControlFlowNode {
+    ConditionalControlFlowNode() {
+      // A conditional node is one with at least one of a true or false successor
+      (exists(getATrueSuccessor()) or exists(getAFalseSuccessor()))
+    }
+  }
+
+  /**
+   * Holds if the `ConditionalNode` has an infeasible `path` according to the control flow graph library.
+   */
+  predicate hasCFGDeducedInfeasiblePath(
+    ConditionalControlFlowNode cond, boolean infeasiblePath, string explanation
+  ) {
+    not cond.isFromTemplateInstantiation(_) and
+    // No true successor, so the true path has already been deduced as infeasible
+    not exists(cond.getATrueSuccessor()) and
+    infeasiblePath = true and
+    explanation = "this expression consists of constants which evaluate to false"
+    or
+    // No false successor, so false path has already been deduced as infeasible
+    not exists(cond.getAFalseSuccessor()) and
+    infeasiblePath = false and
+    explanation = "this expression consists of constants which evaluate to true"
+  }
+
+  predicate isConstantRelationalOperation(
+    RelationalOperation rel, boolean infeasiblePath, string explanation
+  ) {
+    /*
+     * This predicate identifies a number of a cases where we can conclusive determine that a relational
+     * operation will always return true or false, based on the ranges for each operand as determined
+     * by the SimpleRangeAnalysis library (and any extensions provide in the Coding Standards library).
+     *
+     * Important note: in order to deduce that an relational operation _always_ returns true or false,
+     * we must ensure that it returns true or false for _all_ possible values of the operands. For
+     * example, it may be tempting to look at this relational operation on these ranges:
+     * ```
+     *   [0..5] < [0..10]
+     * ```
+     * And say that ub(lesser) < ub(greater) and therefore it is `true`, however this is not the case
+     * for all permutations (e.g. 5 < 0).
+     *
+     * Instead, we look at all four permutations of these two dimensions:
+     *  - Equal-to or not equal-to
+     *  - Always true or always false
+     */
+
+    // This restricts the comparison to occur directly within the conditional node
+    // In theory we could also extend this to identify comparisons where the result is stored, then
+    // later read in a conditional control flow node within the same function (using SSA)
+    // Doing so would benefit from path explanations, but would require a more complex analysis
+    rel instanceof ConditionalControlFlowNode and
+    // If at least one operand includes an access of a volatile variable, the range analysis library may
+    // provide inaccurate results, so we ignore this case
+    not rel.getAnOperand().getAChild*().(VariableAccess).getTarget().isVolatile() and
+    exists(boolean isEqual |
+      if
+        rel instanceof GEExpr
+        or
+        rel instanceof LEExpr
+      then isEqual = true
+      else isEqual = false
+    |
+      // Not equal-to/always true
+      // If the largest value of the lesser operand is less than the smallest value of the greater
+      // operand, then the LT/GT comparison is always true
+      // Example: [0..5] < [6..10]
+      upperBound(rel.getLesserOperand()) < lowerBound(rel.getGreaterOperand()) and
+      explanation =
+        rel.getLesserOperand() + " (max value: " + upperBound(rel.getLesserOperand()) +
+          ") is always less than " + rel.getGreaterOperand() + " (minimum value: " +
+          lowerBound(rel.getGreaterOperand()) + ")" and
+      isEqual = false and
+      infeasiblePath = false
+      or
+      // Equal-to/always true
+      // If the largest value of the lesser operand is less than or equal to the smallest value of the
+      // greater operand, then the LTE/GTE comparison is always true
+      // Example: [0..6] <= [6..10]
+      upperBound(rel.getLesserOperand()) <= lowerBound(rel.getGreaterOperand()) and
+      explanation =
+        rel.getLesserOperand() + " (max value: " + upperBound(rel.getLesserOperand()) +
+          ") is always less than or equal to " + rel.getGreaterOperand() + " (minimum value: " +
+          lowerBound(rel.getGreaterOperand()) + ")" and
+      isEqual = true and
+      infeasiblePath = false
+      or
+      // Equal to/always false
+      // If the largest value of the greater operand is less than the smallest value of the lesser
+      // operand, then the LTE/GTE comparison is always false
+      // Example: [6..10] <= [0..5]
+      upperBound(rel.getGreaterOperand()) < lowerBound(rel.getLesserOperand()) and
+      explanation =
+        rel.getGreaterOperand() + " (max value: " + upperBound(rel.getGreaterOperand()) +
+          ") is always less than " + rel.getLesserOperand() + " (minimum value: " +
+          lowerBound(rel.getLesserOperand()) + ")" and
+      isEqual = true and
+      infeasiblePath = true
+      or
+      // Equal to/always true
+      // If the largest value of the greater operand is less than or equal to the smallest value of the
+      // lesser operand, then the LT/GT comparison is always false
+      // Example: [6..10] < [0..6]
+      upperBound(rel.getGreaterOperand()) <= lowerBound(rel.getLesserOperand()) and
+      explanation =
+        rel.getGreaterOperand() + " (max value: " + upperBound(rel.getGreaterOperand()) +
+          ") is always less than or equal to " + rel.getLesserOperand() + " (minimum value: " +
+          lowerBound(rel.getLesserOperand()) + ")" and
+      isEqual = false and
+      infeasiblePath = true
+    )
+  }
+
+  /**
+   * Holds if the `ConditionalNode` has an infeasible `path` for the reason given in `explanation`.
+   */
+  predicate hasInfeasiblePath(ConditionalControlFlowNode node, string message) {
+    exists(boolean infeasiblePath, string explanation |
+      if node.isFromUninstantiatedTemplate(_)
+      then message = "The path is unreachable in a template."
+      else message = "The " + infeasiblePath + " path is infeasible because " + explanation + "."
+    |
+      hasCFGDeducedInfeasiblePath(node, infeasiblePath, explanation) and
+      not isConstantRelationalOperation(node, infeasiblePath, _)
+      or
+      isConstantRelationalOperation(node, infeasiblePath, explanation)
+    )
+  }
+}
+
+module InvariantCondition<InvariantConditionConfigSig Config> {
+  query predicate problems(Impl::ConditionalControlFlowNode cond, string explanation) {
+    not isExcluded(cond, Config::getQuery()) and
+    Impl::hasInfeasiblePath(cond, explanation) and
+    not Config::isException(cond)
+  }
+}