Fix #14769 FP unreadVariable with address in chained assignment of unused variable (#8926)

Author: chrchr-github

lib/checkunusedvar.cpp

@@ -1009,7 +1009,7 @@ void CheckUnusedVarImpl::checkFunctionVariableUsage_iterateScopes(const Scope* c
             const Token * const equal = skipBracketsAndMembers(tok->next());
 
             // checked for chained assignments
-            if (tok != start && equal && equal->str() == "=") {
+            if (tok != start && (Token::simpleMatch(equal, "=") || (start->astParent() && Token::simpleMatch(start->astParent()->astParent(), "=")))) {
                 const nonneg int varId = tok->varId();
                 const Variables::VariableUsage * const var = variables.find(varId);
 

test/testunusedvar.cpp

@@ -3370,6 +3370,14 @@ class TestUnusedVar : public TestFixture {
                               "    return a;\n"
                               "}\n");
         ASSERT_EQUALS("[test.cpp:5:14]: (style) Variable 'b[c]' is assigned a value that is never used. [unreadVariable]\n", errout_str());
+
+        functionVariableUsage("int f() {\n" // #14769
+                              "    int i = 2;\n"
+                              "    const int *a, *c;\n"
+                              "    a = c = &i;\n"
+                              "    return *a;\n"
+                              "}\n");
+        ASSERT_EQUALS("[test.cpp:4:11]: (style) Variable 'c' is assigned a value that is never used. [unreadVariable]\n", errout_str());
     }
 
     void localvar24() { // ticket #1803