Declarations6: add RULE-18-7

Author: knewbury01

c/cert/src/rules/DCL38-C/DeclaringAFlexibleArrayMember.ql

@@ -15,29 +15,12 @@
 
 import cpp
 import codingstandards.c.cert
-
-/**
- * A member with the type array that is last in a struct
- * includes any sized array (either specified or not)
- */
-class FlexibleArrayMember extends MemberVariable {
-  Struct s;
-
-  FlexibleArrayMember() {
-    this.getType() instanceof ArrayType and
-    this.getDeclaringType() = s and
-    not exists(int i, int j |
-      s.getAMember(i) = this and
-      exists(s.getAMember(j)) and
-      j > i
-    )
-  }
-}
+import codingstandards.c.Variable
 
 from VariableDeclarationEntry m, ArrayType a
 where
   not isExcluded(m, Declarations2Package::declaringAFlexibleArrayMemberQuery()) and
   m.getType() = a and
-  m.getVariable() instanceof FlexibleArrayMember and
+  m.getVariable() instanceof FlexibleArrayMemberCandidate and
   a.getArraySize() = 1
 select m, "Incorrect syntax used for declaring this flexible array member."

c/common/src/codingstandards/c/Variable.qll

@@ -6,3 +6,35 @@ class VlaVariable extends Variable {
   /* Extractor workaround do determine if a VLA array has the specifier volatile.*/
   override predicate isVolatile() { this.getType().(ArrayType).getBaseType().isVolatile() }
 }
+
+/**
+ * A flexible array member
+ * ie member with the type array that is last in a struct
+ * has no size specified
+ */
+class FlexibleArrayMember extends FlexibleArrayMemberCandidate {
+  FlexibleArrayMember() {
+    exists(ArrayType t |
+      this.getType() = t and
+      not exists(t.getSize())
+    )
+  }
+}
+
+/**
+ * A member with the type array that is last in a struct
+ * includes any sized array (either specified or not)
+ */
+class FlexibleArrayMemberCandidate extends MemberVariable {
+  Struct s;
+
+  FlexibleArrayMemberCandidate() {
+    this.getType() instanceof ArrayType and
+    this.getDeclaringType() = s and
+    not exists(int i, int j |
+      s.getAMember(i) = this and
+      exists(s.getAMember(j)) and
+      j > i
+    )
+  }
+}

c/misra/src/rules/RULE-18-7/FlexibleArrayMembersDeclared.ql

@@ -0,0 +1,19 @@
+/**
+ * @id c/misra/flexible-array-members-declared
+ * @name RULE-18-7: Flexible array members shall not be declared
+ * @description The use of flexible array members can lead to unexpected program behaviour.
+ * @kind problem
+ * @precision very-high
+ * @problem.severity error
+ * @tags external/misra/id/rule-18-7
+ *       correctness
+ *       external/misra/obligation/required
+ */
+
+import cpp
+import codingstandards.c.misra
+import codingstandards.c.Variable
+
+from FlexibleArrayMember f
+where not isExcluded(f, Declarations6Package::flexibleArrayMembersDeclaredQuery())
+select f, "Flexible array member declared."

c/misra/test/rules/RULE-18-7/FlexibleArrayMembersDeclared.expected

@@ -0,0 +1 @@
+| test.c:8:7:8:7 | b | Flexible array member declared. |

c/misra/test/rules/RULE-18-7/FlexibleArrayMembersDeclared.qlref

@@ -0,0 +1 @@
+rules/RULE-18-7/FlexibleArrayMembersDeclared.ql

c/misra/test/rules/RULE-18-7/test.c

@@ -0,0 +1,20 @@
+struct s {
+  int a;
+  int b[1]; // COMPLIANT
+};
+
+struct s1 {
+  int a;
+  int b[]; // NON_COMPLIANT
+};
+
+struct s2 {
+  int a;
+  int b[2]; // COMPLIANT
+};
+
+struct s3 {
+  int a;
+  int b[1]; // COMPLIANT
+  int a1;
+};

cpp/common/src/codingstandards/cpp/exclusions/c/Declarations6.qll

@@ -5,6 +5,7 @@ import codingstandards.cpp.exclusions.RuleMetadata
 
 newtype Declarations6Query =
   TFunctionDeclaredImplicitlyQuery() or
+  TFlexibleArrayMembersDeclaredQuery() or
   TIdentifiersWithExternalLinkageNotUniqueQuery() or
   TIdentifiersWithInternalLinkageNotUniqueQuery() or
   TInlineFunctionNotDeclaredStaticStorageQuery() or
@@ -21,6 +22,15 @@ predicate isDeclarations6QueryMetadata(Query query, string queryId, string ruleI
   ruleId = "RULE-17-3" and
   category = "mandatory"
   or
+  query =
+    // `Query` instance for the `flexibleArrayMembersDeclared` query
+    Declarations6Package::flexibleArrayMembersDeclaredQuery() and
+  queryId =
+    // `@id` for the `flexibleArrayMembersDeclared` query
+    "c/misra/flexible-array-members-declared" and
+  ruleId = "RULE-18-7" and
+  category = "required"
+  or
   query =
     // `Query` instance for the `identifiersWithExternalLinkageNotUnique` query
     Declarations6Package::identifiersWithExternalLinkageNotUniqueQuery() and
@@ -75,6 +85,13 @@ module Declarations6Package {
       TQueryC(TDeclarations6PackageQuery(TFunctionDeclaredImplicitlyQuery()))
   }
 
+  Query flexibleArrayMembersDeclaredQuery() {
+    //autogenerate `Query` type
+    result =
+      // `Query` type for `flexibleArrayMembersDeclared` query
+      TQueryC(TDeclarations6PackageQuery(TFlexibleArrayMembersDeclaredQuery()))
+  }
+
   Query identifiersWithExternalLinkageNotUniqueQuery() {
     //autogenerate `Query` type
     result =

rule_packages/c/Declarations6.json

@@ -20,6 +20,25 @@
       ],
       "title": "A function shall not be declared implicitly"
     },
+    "RULE-18-7": {
+      "properties": {
+        "obligation": "required"
+      },
+      "queries": [
+        {
+          "description": "The use of flexible array members can lead to unexpected program behaviour.",
+          "kind": "problem",
+          "name": "Flexible array members shall not be declared",
+          "precision": "very-high",
+          "severity": "error",
+          "short_name": "FlexibleArrayMembersDeclared",
+          "tags": [
+            "correctness"
+          ]
+        }
+      ],
+      "title": "Flexible array members shall not be declared"
+    },
     "RULE-5-8": {
       "properties": {
         "obligation": "required"

rules.csv

@@ -725,7 +725,7 @@ c,MISRA-C-2012,RULE-18-3,Yes,Required,,,"The relational operators >, >=, < and <
 c,MISRA-C-2012,RULE-18-4,Yes,Advisory,,,"The +, -, += and -= operators should not be applied to an expression of pointer type",M5-0-15,Pointers1,Medium,
 c,MISRA-C-2012,RULE-18-5,Yes,Advisory,,,Declarations should contain no more than two levels of pointer nesting,A5-0-3,Pointers1,Import,
 c,MISRA-C-2012,RULE-18-6,Yes,Required,,,The address of an object with automatic storage shall not be copied to another object that persists after the first object has ceased to exist,M7-5-2,Pointers1,Import,
-c,MISRA-C-2012,RULE-18-7,Yes,Required,,,Flexible array members shall not be declared,,Declarations,Medium,
+c,MISRA-C-2012,RULE-18-7,Yes,Required,,,Flexible array members shall not be declared,,Declarations6,Medium,
 c,MISRA-C-2012,RULE-18-8,Yes,Required,,,Variable-length array types shall not be used,,Declarations,Medium,
 c,MISRA-C-2012,RULE-19-1,Yes,Mandatory,,,An object shall not be assigned or copied to an overlapping object,M0-2-1,Contracts,Hard,
 c,MISRA-C-2012,RULE-19-2,Yes,Advisory,,,The union keyword should not be used,A9-5-1,Banned,Import,