Fixed #6226 (false negative: printf format check for user defined array type)

lib/checkio.cpp

@@ -1549,6 +1549,20 @@ bool CheckIO::ArgumentInfo::isStdVectorOrString()
                 return true;
             }
         }
+    } else if (variableInfo->type()) {
+        const Scope * classScope = variableInfo->type()->classScope;
+        if (classScope) {
+            std::list<Function>::const_iterator functions;
+            for (functions = classScope->functionList.begin();
+                 functions != classScope->functionList.end(); ++functions) {
+                if (functions->name() == "operator[]") {
+                    if (Token::Match(functions->retDef, "%type% &")) {
+                        typeToken = functions->retDef;
+                        return true;
+                    }
+                }
+            }
+        }
     }
 
     return false;

test/testio.cpp

@@ -3100,6 +3100,19 @@ private:
         ASSERT_EQUALS("[test.cpp:4]: (warning) %s in format string (no. 1) requires 'char *' but the argument type is 'std::string'.\n"
                       "[test.cpp:4]: (warning) %s in format string (no. 2) requires 'char *' but the argument type is 'int'.\n", errout.str());
 
+        check("template <class T, size_t S>\n"
+              "struct Array {\n"
+              "    T data[S];\n"
+              "    T & operator [] (size_t i) { return data[i]; }\n"
+              "};\n"
+              "void foo() {\n"
+              "    Array<int, 10> array1;\n"
+              "    Array<float, 10> array2;\n"
+              "    printf(\"%u %u\", array1[0], array2[0]);\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:9]: (warning) %u in format string (no. 1) requires 'unsigned int' but the argument type is 'int'.\n"
+                      "[test.cpp:9]: (warning) %u in format string (no. 2) requires 'unsigned int' but the argument type is 'float'.\n", errout.str());
+
     }
 
     void testPosixPrintfScanfParameterPosition() { // #4900  - No support for parameters in format strings