Implement Rule 22-4-1, only assign literal 0 to errno.

cpp/common/src/codingstandards/cpp/exclusions/cpp/Preconditions4.qll

@@ -0,0 +1,26 @@
+//** THIS FILE IS AUTOGENERATED, DO NOT MODIFY DIRECTLY.  **/
+import cpp
+import RuleMetadata
+import codingstandards.cpp.exclusions.RuleMetadata
+
+newtype Preconditions4Query = TInvalidAssignmentToErrnoQuery()
+
+predicate isPreconditions4QueryMetadata(Query query, string queryId, string ruleId, string category) {
+  query =
+    // `Query` instance for the `invalidAssignmentToErrno` query
+    Preconditions4Package::invalidAssignmentToErrnoQuery() and
+  queryId =
+    // `@id` for the `invalidAssignmentToErrno` query
+    "cpp/misra/invalid-assignment-to-errno" and
+  ruleId = "RULE-22-4-1" and
+  category = "required"
+}
+
+module Preconditions4Package {
+  Query invalidAssignmentToErrnoQuery() {
+    //autogenerate `Query` type
+    result =
+      // `Query` type for `invalidAssignmentToErrno` query
+      TQueryCPP(TPreconditions4PackageQuery(TInvalidAssignmentToErrnoQuery()))
+  }
+}

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

@@ -44,6 +44,7 @@ import Operators
 import OrderOfEvaluation
 import OutOfBounds
 import Pointers
+import Preconditions4
 import Representation
 import Scope
 import SideEffects1
@@ -103,6 +104,7 @@ newtype TCPPQuery =
   TOrderOfEvaluationPackageQuery(OrderOfEvaluationQuery q) or
   TOutOfBoundsPackageQuery(OutOfBoundsQuery q) or
   TPointersPackageQuery(PointersQuery q) or
+  TPreconditions4PackageQuery(Preconditions4Query q) or
   TRepresentationPackageQuery(RepresentationQuery q) or
   TScopePackageQuery(ScopeQuery q) or
   TSideEffects1PackageQuery(SideEffects1Query q) or
@@ -162,6 +164,7 @@ predicate isQueryMetadata(Query query, string queryId, string ruleId, string cat
   isOrderOfEvaluationQueryMetadata(query, queryId, ruleId, category) or
   isOutOfBoundsQueryMetadata(query, queryId, ruleId, category) or
   isPointersQueryMetadata(query, queryId, ruleId, category) or
+  isPreconditions4QueryMetadata(query, queryId, ruleId, category) or
   isRepresentationQueryMetadata(query, queryId, ruleId, category) or
   isScopeQueryMetadata(query, queryId, ruleId, category) or
   isSideEffects1QueryMetadata(query, queryId, ruleId, category) or

cpp/common/src/codingstandards/cpp/standardlibrary/Errno.qll

@@ -0,0 +1,6 @@
+import cpp
+
+predicate isErrno(VariableAccess va) {
+  va.getTarget().hasName("errno") or
+  va.getTarget().hasName("__errno")
+}

cpp/common/test/includes/standard-library/errno.h

@@ -2,4 +2,7 @@
 #define _GHLIBCPP_ERRNO
 int __errno;
 #define errno __errno
+#define EINVAL 22
+#define ERANGE 34
+#define EDOM 33
 #endif // _GHLIBCPP_ERRNO

cpp/common/test/includes/standard-library/string

@@ -248,6 +248,8 @@ public:
   int compare(size_type pos1, size_type n1, const charT *s) const;
   int compare(size_type pos1, size_type n1, const charT *s, size_type n2) const;
 
+  bool empty() const noexcept;
+
   void reserve(size_type new_cap = 0);
 };
 

cpp/misra/src/rules/RULE-22-4-1/InvalidAssignmentToErrno.ql

@@ -0,0 +1,35 @@
+/**
+ * @id cpp/misra/invalid-assignment-to-errno
+ * @name RULE-22-4-1: The literal value zero shall be the only value assigned to errno
+ * @description C++ provides better options for error handling than the use of errno. Errno should
+ *              not be used for reporting errors within project code.
+ * @kind problem
+ * @precision very-high
+ * @problem.severity error
+ * @tags external/misra/id/rule-22-4-1
+ *       scope/single-translation-unit
+ *       maintainability
+ *       external/misra/enforcement/decidable
+ *       external/misra/obligation/required
+ */
+
+import cpp
+import codingstandards.cpp.misra
+import codingstandards.cpp.standardlibrary.Errno
+import codingstandards.cpp.Literals
+
+from Assignment assign, VariableAccess errno, Expr rvalue, string message
+where
+  not isExcluded(assign, Preconditions4Package::invalidAssignmentToErrnoQuery()) and
+  assign.getLValue() = errno and
+  isErrno(errno) and
+  assign.getRValue().getExplicitlyConverted() = rvalue and
+  (
+    not rvalue instanceof LiteralZero and
+    message = "Assignment to 'errno' with non-zero literal value '" + rvalue.toString() + "'."
+    or
+    assign instanceof AssignOperation and
+    message =
+      "Compound assignment to 'errno' with operator '" + assign.getOperator() + "' is not allowed."
+  )
+select assign, message

cpp/misra/test/rules/RULE-22-4-1/InvalidAssignmentToErrno.expected

@@ -0,0 +1,37 @@
+| test.cpp:26:3:26:13 | ... = ... | Assignment to 'errno' with non-zero literal value '0.0'. |
+| test.cpp:27:3:27:14 | ... = ... | Assignment to 'errno' with non-zero literal value '0.0'. |
+| test.cpp:31:3:31:11 | ... = ... | Assignment to 'errno' with non-zero literal value '1'. |
+| test.cpp:32:3:32:12 | ... = ... | Assignment to 'errno' with non-zero literal value '42'. |
+| test.cpp:33:3:33:12 | ... = ... | Assignment to 'errno' with non-zero literal value '- ...'. |
+| test.cpp:39:3:39:22 | ... = ... | Assignment to 'errno' with non-zero literal value '42'. |
+| test.cpp:49:3:49:12 | ... = ... | Assignment to 'errno' with non-zero literal value 'l1'. |
+| test.cpp:50:3:50:12 | ... = ... | Assignment to 'errno' with non-zero literal value 'l2'. |
+| test.cpp:51:3:51:12 | ... = ... | Assignment to 'errno' with non-zero literal value 'l3'. |
+| test.cpp:52:3:52:12 | ... = ... | Assignment to 'errno' with non-zero literal value 'l4'. |
+| test.cpp:53:3:53:12 | ... = ... | Assignment to 'errno' with non-zero literal value 'l5'. |
+| test.cpp:57:3:57:16 | ... = ... | Assignment to 'errno' with non-zero literal value '22'. |
+| test.cpp:58:3:58:16 | ... = ... | Assignment to 'errno' with non-zero literal value '34'. |
+| test.cpp:59:3:59:14 | ... = ... | Assignment to 'errno' with non-zero literal value '33'. |
+| test.cpp:63:3:63:15 | ... = ... | Assignment to 'errno' with non-zero literal value '... + ...'. |
+| test.cpp:64:3:64:15 | ... = ... | Assignment to 'errno' with non-zero literal value '... - ...'. |
+| test.cpp:65:3:65:15 | ... = ... | Assignment to 'errno' with non-zero literal value '... * ...'. |
+| test.cpp:66:3:66:35 | ... = ... | Assignment to 'errno' with non-zero literal value '... - ...'. |
+| test.cpp:70:3:70:11 | ... = ... | Assignment to 'errno' with non-zero literal value '5'. |
+| test.cpp:71:3:71:12 | ... += ... | Compound assignment to 'errno' with operator '+=' is not allowed. |
+| test.cpp:72:3:72:12 | ... -= ... | Assignment to 'errno' with non-zero literal value '5'. |
+| test.cpp:72:3:72:12 | ... -= ... | Compound assignment to 'errno' with operator '-=' is not allowed. |
+| test.cpp:73:3:73:12 | ... *= ... | Compound assignment to 'errno' with operator '*=' is not allowed. |
+| test.cpp:74:3:74:12 | ... /= ... | Assignment to 'errno' with non-zero literal value '1'. |
+| test.cpp:74:3:74:12 | ... /= ... | Compound assignment to 'errno' with operator '/=' is not allowed. |
+| test.cpp:81:3:81:14 | ... = ... | Assignment to 'errno' with non-zero literal value 'call to operator()'. |
+| test.cpp:82:3:82:14 | ... = ... | Assignment to 'errno' with non-zero literal value 'call to operator()'. |
+| test.cpp:86:3:86:29 | ... = ... | Assignment to 'errno' with non-zero literal value 'static_cast<int>...'. |
+| test.cpp:87:3:87:31 | ... = ... | Assignment to 'errno' with non-zero literal value 'static_cast<int>...'. |
+| test.cpp:88:3:88:16 | ... = ... | Assignment to 'errno' with non-zero literal value '(int)...'. |
+| test.cpp:89:3:89:16 | ... = ... | Assignment to 'errno' with non-zero literal value '(int)...'. |
+| test.cpp:108:3:108:40 | ... = ... | Assignment to 'errno' with non-zero literal value 'reinterpret_cast<int>...'. |
+| test.cpp:110:3:110:35 | ... = ... | Assignment to 'errno' with non-zero literal value 'reinterpret_cast<int>...'. |
+| test.cpp:111:3:111:35 | ... = ... | Assignment to 'errno' with non-zero literal value 'reinterpret_cast<int>...'. |
+| test.cpp:113:3:113:40 | ... = ... | Assignment to 'errno' with non-zero literal value 'reinterpret_cast<int>...'. |
+| test.cpp:122:3:122:13 | ... = ... | Assignment to 'errno' with non-zero literal value '48'. |
+| test.cpp:128:3:128:14 | ... = ... | Assignment to 'errno' with non-zero literal value '1'. |

cpp/misra/test/rules/RULE-22-4-1/InvalidAssignmentToErrno.qlref

@@ -0,0 +1 @@
+rules/RULE-22-4-1/InvalidAssignmentToErrno.ql

cpp/misra/test/rules/RULE-22-4-1/test.cpp

@@ -0,0 +1,129 @@
+#include <cerrno>
+#include <cstdint>
+#include <optional>
+#include <string>
+
+void errnoSettingFunction();
+void handleError();
+void f();
+
+#define OK 0
+#define CUSTOM_ERROR 42
+#define ZERO_MACRO 0
+
+void test_literal_zero_assignment() {
+  errno = 0; // COMPLIANT
+}
+
+void test_different_zero_literal_formats() {
+  errno = 0;   // COMPLIANT - decimal zero literal
+  errno = 0x0; // COMPLIANT - hexadecimal zero literal
+  errno = 00;  // COMPLIANT - octal zero literal
+  errno = 0b0; // COMPLIANT - binary zero literal
+}
+
+void test_floating_point_zero_literals() {
+  errno = 0.0;  // NON_COMPLIANT - floating point literal, not integer literal
+  errno = 0.0f; // NON_COMPLIANT - floating point literal, not integer literal
+}
+
+void test_non_zero_literal_assignment() {
+  errno = 1;  // NON_COMPLIANT
+  errno = 42; // NON_COMPLIANT
+  errno = -1; // NON_COMPLIANT
+}
+
+void test_macro_assignments() {
+  errno = OK;           // COMPLIANT - expands to literal 0
+  errno = ZERO_MACRO;   // COMPLIANT - expands to literal 0
+  errno = CUSTOM_ERROR; // NON_COMPLIANT - expands to non-zero literal
+}
+
+void test_variable_assignments() {
+  std::uint32_t l1 = 0;
+  const std::uint32_t l2 = 0;
+  constexpr std::uint32_t l3 = 0;
+  std::uint32_t l4 = 42;
+  const std::uint32_t l5 = 42;
+
+  errno = l1; // NON_COMPLIANT - variable, not literal
+  errno = l2; // NON_COMPLIANT - constant variable, not literal
+  errno = l3; // NON_COMPLIANT - constexpr variable, not literal
+  errno = l4; // NON_COMPLIANT - variable with non-zero value
+  errno = l5; // NON_COMPLIANT - constant variable with non-zero value
+}
+
+void test_standard_error_macros() {
+  errno = EINVAL; // NON_COMPLIANT - standard error macro
+  errno = ERANGE; // NON_COMPLIANT - standard error macro
+  errno = EDOM;   // NON_COMPLIANT - standard error macro
+}
+
+void test_expressions() {
+  errno = 0 + 0;                     // NON_COMPLIANT - expression, not literal
+  errno = 1 - 1;                     // NON_COMPLIANT - expression, not literal
+  errno = 0 * 5;                     // NON_COMPLIANT - expression, not literal
+  errno = sizeof(int) - sizeof(int); // NON_COMPLIANT - expression, not literal
+}
+
+void test_compound_assignments() {
+  errno = 5;  // NON_COMPLIANT - initial assignment to non-zero value
+  errno += 0; // NON_COMPLIANT - compound assignment, not simple assignment
+  errno -= 5; // NON_COMPLIANT - compound assignment, not simple assignment
+  errno *= 0; // NON_COMPLIANT - compound assignment, not simple assignment
+  errno /= 1; // NON_COMPLIANT - compound assignment, not simple assignment
+}
+
+void test_function_return_values() {
+  auto l1 = []() { return 0; };
+  auto l2 = []() { return 42; };
+
+  errno = l1(); // NON_COMPLIANT - function return value, not literal
+  errno = l2(); // NON_COMPLIANT - function return value, not literal
+}
+
+void test_cast_expressions() {
+  errno = static_cast<int>(0);   // NON_COMPLIANT - cast expression
+  errno = static_cast<int>(0.0); // NON_COMPLIANT - cast expression
+  errno = (int)0;                // NON_COMPLIANT - C-style cast
+  errno = int(0);                // NON_COMPLIANT - functional cast
+}
+
+void test_reading_errno_is_allowed() {
+  std::uint32_t l1 = errno; // COMPLIANT - reading errno is allowed
+  if (errno != 0) {         // COMPLIANT - reading errno is allowed
+    handleError();
+  }
+
+  errnoSettingFunction();
+  std::uint32_t l2 = 0;
+  if (errno != l2) { // COMPLIANT - reading errno is allowed
+    handleError();
+  }
+}
+
+void test_pointer_and_null_assignments() {
+label:
+  static const int x = 0;
+  errno = reinterpret_cast<int>(nullptr); // NON_COMPLIANT - nullptr is
+                                          // not an integer literal
+  errno = reinterpret_cast<int>(&x); // NON_COMPLIANT - pointer cast to integer
+  errno = reinterpret_cast<int>(&f); // NON_COMPLIANT - pointer cast to
+                                     // integer
+  errno = reinterpret_cast<int>(&&label); // NON_COMPLIANT - pointer
+                                          // cast to integer
+  errno = NULL; // NON_COMPLIANT[FALSE_NEGATIVE] - NULL may expand to 0 but not
+                // literal
+}
+
+void test_character_literals() {
+  errno = '\0'; // NON_COMPLIANT[FALSE_NEGATIVE] - character literal, not
+                // integer literal
+  errno = '0';  // NON_COMPLIANT - character '0' has value 48
+}
+
+void test_boolean_literals() {
+  errno = false; // NON_COMPLIANT[FALSE_NEGATIVE] - boolean literal, not integer
+                 // literal
+  errno = true;  // NON_COMPLIANT - boolean literal with non-zero value
+}

rule_packages/cpp/Preconditions4.json

@@ -0,0 +1,25 @@
+{
+  "MISRA-C++-2023": {
+    "RULE-22-4-1": {
+      "properties": {
+        "enforcement": "decidable",
+        "obligation": "required"
+      },
+      "queries": [
+        {
+          "description": "C++ provides better options for error handling than the use of errno. Errno should not be used for reporting errors within project code.",
+          "kind": "problem",
+          "name": "The literal value zero shall be the only value assigned to errno",
+          "precision": "very-high",
+          "severity": "error",
+          "short_name": "InvalidAssignmentToErrno",
+          "tags": [
+            "scope/single-translation-unit",
+            "maintainability"
+          ]
+        }
+      ],
+      "title": "The literal value zero shall be the only value assigned to errno"
+    }
+  }
+}

rules.csv

@@ -987,7 +987,7 @@ cpp,MISRA-C++-2023,RULE-21-10-1,Yes,Required,Decidable,Single Translation Unit,T
 cpp,MISRA-C++-2023,RULE-21-10-2,Yes,Required,Decidable,Single Translation Unit,The standard header file <csetjmp> shall not be used,ERR52-CPP,BannedAPIs,Easy,
 cpp,MISRA-C++-2023,RULE-21-10-3,Yes,Required,Decidable,Single Translation Unit,The facilities provided by the standard header file <csignal> shall not be used,M18-7-1,ImportMisra23,Import,
 cpp,MISRA-C++-2023,RULE-22-3-1,Yes,Required,Decidable,Single Translation Unit,The assert macro shall not be used with a constant-expression,,Preconditions,Easy,
-cpp,MISRA-C++-2023,RULE-22-4-1,Yes,Required,Decidable,Single Translation Unit,The literal value zero shall be the only value assigned to errno,,Preconditions,Easy,
+cpp,MISRA-C++-2023,RULE-22-4-1,Yes,Required,Decidable,Single Translation Unit,The literal value zero shall be the only value assigned to errno,,Preconditions4,Easy,
 cpp,MISRA-C++-2023,RULE-23-11-1,Yes,Advisory,Decidable,Single Translation Unit,The raw pointer constructors of std::shared_ptr and std::unique_ptr should not be used,,BannedAPIs,Easy,
 cpp,MISRA-C++-2023,RULE-24-5-1,Yes,Required,Decidable,Single Translation Unit,The character handling functions from <cctype> and <cwctype> shall not be used,,BannedAPIs,Easy,
 cpp,MISRA-C++-2023,RULE-24-5-2,Yes,Required,Decidable,Single Translation Unit,"The C++ Standard Library functions memcpy, memmove and memcmp from <cstring> shall not be used",,BannedAPIs,Easy,