Fixed #934 (new check: missuse of std::cout)

lib/checkother.cpp

@@ -664,6 +664,29 @@ void CheckOther::switchCaseFallThrough(const Token *tok)
                 "switchCaseFallThrough", "Switch falls through case without comment");
 }
 
+//---------------------------------------------------------------------------
+//    std::cout << std::cout;
+//---------------------------------------------------------------------------
+void CheckOther::checkCoutCerrMisusage()
+{
+    bool firstCout = false;
+    for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
+        if (Token::Match(tok, "std :: cout|cerr")) {
+            if (firstCout && tok->strAt(-1) == "<<" && tok->strAt(3) != ".") {
+                coutCerrMisusageError(tok, tok->strAt(2));
+                firstCout = false;
+            } else if (tok->strAt(3) == "<<")
+                firstCout = true;
+        } else if (firstCout && tok->str() == ";")
+            firstCout = false;
+    }
+}
+
+void CheckOther::coutCerrMisusageError(const Token* tok, const std::string& streamName)
+{
+    reportError(tok, Severity::error, "coutCerrMisusage", "Invalid usage of output stream: '<< std::" + streamName + "'.");
+}
+
 //---------------------------------------------------------------------------
 //    int x = 1;
 //    x = x;            // <- redundant assignment to self

lib/checkother.h

@@ -89,6 +89,7 @@ public:
         checkOther.checkFflushOnInputStream();
         checkOther.invalidScanf();
 
+        checkOther.checkCoutCerrMisusage();
         checkOther.checkIncorrectLogicOperator();
         checkOther.checkMisusedScopedObject();
         checkOther.checkCatchExceptionByValue();
@@ -171,6 +172,9 @@ public:
     /** @brief %Check for switch case fall through without comment */
     void checkSwitchCaseFallThrough();
 
+    /** @brief %Check for missusage of std::cout */
+    void checkCoutCerrMisusage();
+
     /** @brief %Check for assigning a variable to itself*/
     void checkSelfAssignment();
 
@@ -246,6 +250,7 @@ public:
     void variableScopeError(const Token *tok, const std::string &varname);
     void strPlusCharError(const Token *tok);
     void zerodivError(const Token *tok);
+    void coutCerrMisusageError(const Token* tok, const std::string& streamName);
     void mathfunctionCallError(const Token *tok, const unsigned int numParam = 1);
     void fflushOnInputStreamError(const Token *tok, const std::string &varname);
     void redundantAssignmentInSwitchError(const Token *tok, const std::string &varname);
@@ -289,6 +294,7 @@ public:
         c.misusedScopeObjectError(NULL, "varname");
         c.sizeofForArrayParameterError(0);
         c.sizeofForNumericParameterError(0);
+        c.coutCerrMisusageError(0, "cout");
 
         // style/warning
         c.cstyleCastError(0);
@@ -345,6 +351,7 @@ public:
                "* sizeof for array given as function argument\n"
                "* sizeof for numeric given as function argument\n"
                "* incorrect length arguments for 'substr' and 'strncmp'\n"
+               "* invalid usage of output stream. For example: std::cout << std::cout;'\n"
 
                // style
                "* C-style pointer cast in cpp file\n"

test/testother.cpp

@@ -81,6 +81,8 @@ private:
         TEST_CASE(switchFallThroughCase);
         TEST_CASE(duplicateBreak);
 
+        TEST_CASE(coutCerrMisusage);
+
         TEST_CASE(selfAssignment);
         TEST_CASE(testScanf1);
         TEST_CASE(testScanf2);
@@ -180,6 +182,7 @@ private:
         checkOther.checkFflushOnInputStream();
         checkOther.checkSelfAssignment();
         checkOther.invalidScanf();
+        checkOther.checkCoutCerrMisusage();
         checkOther.checkMisusedScopedObject();
         checkOther.checkIncorrectLogicOperator();
         checkOther.checkCatchExceptionByValue();
@@ -3747,6 +3750,39 @@ private:
             "}");
         ASSERT_EQUALS("", errout.str());
     }
+
+    void coutCerrMisusage() {
+        check(
+            "void foo() {\n"
+            "  std::cout << std::cout;\n"
+            "}");
+        ASSERT_EQUALS("[test.cpp:2]: (error) Invalid usage of output stream: '<< std::cout'.\n", errout.str());
+
+        check(
+            "void foo() {\n"
+            "  std::cout << \"xyz\" << std::cout;\n"
+            "}");
+        ASSERT_EQUALS("[test.cpp:2]: (error) Invalid usage of output stream: '<< std::cout'.\n", errout.str());
+
+        check(
+            "void foo(int i) {\n"
+            "  std::cout << i << std::cerr;\n"
+            "}");
+        ASSERT_EQUALS("[test.cpp:2]: (error) Invalid usage of output stream: '<< std::cerr'.\n", errout.str());
+
+        check(
+            "void foo() {\n"
+            "  std::cout << \"xyz\";\n"
+            "  std::cout << \"xyz\";\n"
+            "}");
+        ASSERT_EQUALS("", errout.str());
+
+        check(
+            "void foo() {\n"
+            "  std::cout << std::cout.good();\n"
+            "}");
+        ASSERT_EQUALS("", errout.str());
+    }
 };
 
 REGISTER_TEST(TestOther)