Fix 14136: False positive: constParameterReference when using void cast (#7829)

Author: pfultz2

lib/astutils.cpp

@@ -429,6 +429,12 @@ bool isStlStringType(const Token* tok)
            (Token::simpleMatch(tok, "std :: basic_string <") && !Token::simpleMatch(tok->linkAt(3), "> ::"));
 }
 
+bool isVoidCast(const Token* tok)
+{
+    return Token::simpleMatch(tok, "(") && tok->isCast() && tok->valueType() &&
+           tok->valueType()->type == ValueType::Type::VOID && tok->valueType()->pointer == 0;
+}
+
 bool isTemporary(const Token* tok, const Library* library, bool unknown)
 {
     if (!tok)

lib/astutils.h

@@ -188,6 +188,8 @@ const Token * astIsVariableComparison(const Token *tok, const std::string &comp,
 bool isVariableDecl(const Token* tok);
 bool isStlStringType(const Token* tok);
 
+bool isVoidCast(const Token* tok);
+
 bool isTemporary(const Token* tok, const Library* library, bool unknown = false);
 
 const Token* previousBeforeAstLeftmostLeaf(const Token* tok);

lib/checkother.cpp

@@ -1641,6 +1641,21 @@ static bool isVariableMutableInInitializer(const Token* start, const Token * end
     return false;
 }
 
+static bool isCastToVoid(const Variable* var)
+{
+    if (!var)
+        return false;
+    if (!var->scope())
+        return false;
+    for (const Token* tok = var->scope()->bodyStart; tok != var->scope()->bodyEnd; tok = tok->next()) {
+        if (tok->varId() != var->declarationId())
+            continue;
+        if (isVoidCast(tok->astParent()))
+            return true;
+    }
+    return false;
+}
+
 void CheckOther::checkConstVariable()
 {
     if ((!mSettings->severity.isEnabled(Severity::style) || mTokenizer->isC()) && !mSettings->isPremiumEnabled("constVariable"))
@@ -1689,6 +1704,8 @@ void CheckOther::checkConstVariable()
             continue;
         if (isStructuredBindingVariable(var)) // TODO: check all bound variables
             continue;
+        if (isCastToVoid(var))
+            continue;
         if (isVariableChanged(var, *mSettings))
             continue;
         const bool hasFunction = function != nullptr;

lib/checkuninitvar.cpp

@@ -1150,11 +1150,6 @@ static bool astIsRhs(const Token *tok)
     return tok && tok->astParent() && tok == tok->astParent()->astOperand2();
 }
 
-static bool isVoidCast(const Token *tok)
-{
-    return Token::simpleMatch(tok, "(") && tok->isCast() && tok->valueType() && tok->valueType()->type == ValueType::Type::VOID && tok->valueType()->pointer == 0;
-}
-
 const Token* CheckUninitVar::isVariableUsage(const Token *vartok, const Library& library, bool pointer, Alloc alloc, int indirect)
 {
     const bool cpp = vartok->isCpp();

test/testother.cpp

@@ -3300,6 +3300,10 @@ class TestOther : public TestFixture {
               "};\n");
         ASSERT_EQUALS("", errout_str());
 
+        // #14136
+        check("void f(int& x) { (void)x; }\n");
+        ASSERT_EQUALS("", errout_str());
+
         check("void e();\n"
               "void g(void);\n"
               "void h(void);\n"
@@ -12173,9 +12177,7 @@ class TestOther : public TestFixture {
               "        for (auto &j : g(std::move(l))) { (void)j; }\n"
               "    }\n"
               "}\n");
-        ASSERT_EQUALS("[test.cpp:4:20]: (style) Variable 'j' can be declared as reference to const [constVariableReference]\n"
-                      "[test.cpp:4:36]: (warning) Access of moved variable 'l'. [accessMoved]\n",
-                      errout_str());
+        ASSERT_EQUALS("[test.cpp:4:36]: (warning) Access of moved variable 'l'. [accessMoved]\n", errout_str());
     }
 
     void moveCallback()