Resolve 371

change_notes/2024-02-16-fix-fps-a5-1-1.md

@@ -0,0 +1,7 @@
+- `A5-1-1` - `LiteralValueUsedOutsideTypeInit.ql`:
+  - Address FP reported in #371. Exclude literals generated by uses of constexpr variables.
+  - Exclude literals used in class template instantiations.
+  - Update the alert message to adhere to the style-guide.
+  - Exclude boolean literals used as template arguments.
+  - Exclude `u` and `U` prefixed char literals.
+  - Exclude literals part of a class aggregate literal.

cpp/autosar/src/rules/A5-1-1/LiteralValueUsedOutsideTypeInit.ql

@@ -18,6 +18,7 @@ import cpp
 import codingstandards.cpp.autosar
 import codingstandards.cpp.LoggingOperation
 import codingstandards.cpp.Literals
+import codingstandards.cpp.Cpp14Literal
 
 from Literal l
 where
@@ -35,11 +36,11 @@ where
   // Exclude literal 0
   not l.getValue() = "0" and
   // Exclude character literals
-  not l instanceof CharLiteral and
+  not l instanceof Cpp14Literal::CharLiteral and
   // Exclude `nullptr`
   not l.getType() instanceof NullPointerType and
   // Exclude boolean `true` and `false`
-  not l.getType() instanceof BoolType and
+  not l instanceof BoolLiteral and
   // Exclude empty string
   not l.getValue() = "" and
   // Template functions use literals to represent calls which are unknown
@@ -51,7 +52,14 @@ where
   // Aggregate literal
   not l = any(ArrayOrVectorAggregateLiteral aal).getAnElementExpr(_).getAChild*() and
   // Ignore x - 1 expressions
-  not exists(SubExpr se | se.getRightOperand() = l and l.getValue() = "1")
-select l,
-  "Literal value " + getTruncatedLiteralText(l) + " used outside of type initialization " +
-    l.getAPrimaryQlClass()
+  not exists(SubExpr se | se.getRightOperand() = l and l.getValue() = "1") and
+  // Exclude compile time computed integral literals as they can appear as integral literals
+  // when used as non-type template arguments.
+  // We limit ourselves to integral literals, because floating point literals as non-type
+  // template arguments are not supported in C++ 14. Those are supported shince C++ 20.
+  not l instanceof CompileTimeComputedIntegralLiteral and
+  // Exclude literals to instantiate a class template per example in the standard
+  // where an type of std::array is intialized with size 5.
+  not l = any(ClassTemplateInstantiation cti).getATemplateArgument() and
+  not l = any(ClassAggregateLiteral cal).getAFieldExpr(_)
+select l, "Literal value '" + getTruncatedLiteralText(l) + "' used outside of type initialization."

cpp/autosar/test/rules/A5-1-1/LiteralValueUsedOutsideTypeInit.expected

@@ -1,5 +1,8 @@
-| test.cpp:5:9:5:25 | constant string | Literal value "constant string" used outside of type initialization StringLiteral |
-| test.cpp:14:23:14:25 | 100 | Literal value 100 used outside of type initialization Literal |
-| test.cpp:54:7:54:7 | 1 | Literal value 1 used outside of type initialization Literal |
-| test.cpp:75:23:75:28 | test | Literal value "test" used outside of type initialization StringLiteral |
-| test.cpp:76:19:76:28 | not okay | Literal value "not okay" used outside of type initialization StringLiteral |
+| test.cpp:5:9:5:25 | constant string | Literal value '"constant string"' used outside of type initialization. |
+| test.cpp:14:23:14:25 | 100 | Literal value '100' used outside of type initialization. |
+| test.cpp:54:7:54:7 | 1 | Literal value '1' used outside of type initialization. |
+| test.cpp:75:23:75:28 | test | Literal value '"test"' used outside of type initialization. |
+| test.cpp:76:19:76:28 | not okay | Literal value '"not okay"' used outside of type initialization. |
+| test.cpp:104:8:104:8 | 4 | Literal value '4' used outside of type initialization. |
+| test.cpp:104:8:104:8 | 4 | Literal value '4' used outside of type initialization. |
+| test.cpp:104:8:104:8 | 4 | Literal value '4' used outside of type initialization. |

cpp/autosar/test/rules/A5-1-1/test.cpp

@@ -80,10 +80,46 @@ void test_not_wrapper_stream(std::ostream &os, const char *str) noexcept {
 #define MACRO_LOG(test_str)                                                    \
   do {                                                                         \
     struct test_struct {                                                       \
-      static const char *get_str() { return static_cast<char *>(test_str); }   \
+      static const char *get_str() {                                           \
+        return static_cast<const char *>(test_str);                            \
+      }                                                                        \
     };                                                                         \
   } while (false)
 
 void f() {
   MACRO_LOG("test"); // COMPLIANT - exclusion
+}
+
+template <typename T> struct S1 { static constexpr size_t value(); };
+
+template <> struct S1<int> {
+  static constexpr size_t value() { return sizeof(int); };
+};
+
+constexpr size_t g1 = S1<int>::value();
+constexpr size_t f1() { return sizeof(int); }
+
+template <typename T, int size> struct S2 {
+  T m1[size]; // COMPLIANT
+  T m2[4];    // NON_COMPLIANT
+};
+
+template <typename T, T val> struct S3 {
+  static constexpr T value = val; // COMPLIANT;
+};
+
+void test_fp_reported_in_371() {
+  struct S2<int, 1> l1;    // COMPLIANT
+  struct S2<int, g1> l2;   // COMPLIANT
+  struct S2<int, f1()> l3; // COMPLIANT
+
+  S3<char16_t, u'\u03c0'> l4;                      // COMPLIANT
+  S3<char16_t, S3<char16_t, u'\u2286'>::value> l5; // COMPLIANT
+  S3<char32_t, U'🌌'> l6;                           // COMPLIANT
+  S3<char32_t, S3<char32_t, U'⭐'>::value> l7;      // COMPLIANT
+
+  constexpr float l8 = 3.14159f;
+#define delta 0.1f
+  for (float i = 0.0f; i < l8; i += delta) { // COMPLIANT
+  }
 }

cpp/common/src/codingstandards/cpp/Cpp14Literal.qll

@@ -82,4 +82,26 @@ module Cpp14Literal {
 
     override string getAPrimaryQlClass() { result = "FloatingLiteral" }
   }
+
+  /**
+   * A character literal.  For example:
+   * ```
+   * char c1 = 'a';
+   * char16_t c2 = u'a';
+   * char32_t c3 = U'a';
+   * wchar_t c4 = L'b';
+   * ```
+   */
+  class CharLiteral extends StandardLibrary::TextLiteral {
+    CharLiteral() { this.getValueText().regexpMatch("(?s)\\s*(L|u|U)?'.*") }
+
+    override string getAPrimaryQlClass() { result = "CharLiteral" }
+
+    /**
+     * Gets the character of this literal. For example `L'a'` has character `"a"`.
+     */
+    string getCharacter() {
+      result = this.getValueText().regexpCapture("(?s)\\s*(L|u|U)?'(.*)'", 1)
+    }
+  }
 }

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

@@ -3,6 +3,7 @@
  */
 
 import cpp
+import codingstandards.cpp.Cpp14Literal
 
 /** Gets `Literal.getValueText()` truncated to at most 20 characters. */
 string getTruncatedLiteralText(Literal l) {
@@ -28,3 +29,38 @@ class Utf16StringLiteral extends StringLiteral {
 class Utf32StringLiteral extends StringLiteral {
   Utf32StringLiteral() { this.getValueText().regexpMatch("(?s)\\s*U\".*") }
 }
+
+/**
+ * A literal resulting from the use of a constexpr
+ * variable, or macro expansion.
+ * We rely on the fact that the value text of a literal is equal to the
+ * `constexpr` variable or macro name.
+ */
+class CompileTimeComputedIntegralLiteral extends Literal {
+  CompileTimeComputedIntegralLiteral() {
+    this.getUnspecifiedType() instanceof IntegralType and
+    // Exclude bool, whose value text is true or false, but the value itself
+    // is 1 or 0.
+    not this instanceof BoolLiteral and
+    // Exclude character literals, whose value text is the quoted character, but the value
+    // is the numeric value of the character.
+    not this instanceof Cpp14Literal::CharLiteral and
+    not this.getValueText()
+        .trim()
+        .regexpMatch("([0-9][0-9']*|0[xX][0-9a-fA-F']+|0b[01']+)[uU]?([lL]{1,2}|[zZ])?") and
+    // Exclude class field initializers whose value text equals the initializer expression, e.g., `x(0)`
+    not any(ConstructorFieldInit cfi).getExpr() = this
+  }
+}
+
+class BoolLiteral extends Literal {
+  BoolLiteral() {
+    this.getType() instanceof BoolType
+    or
+    // When used as non-type template arguments, bool literals might
+    // have been converted to a non-bool type.
+    this.getValue() = "1" and this.getValueText() = "true"
+    or
+    this.getValue() = "0" and this.getValueText() = "false"
+  }
+}