invalidTestForOverflow: Fixed some false negatives (cppcheck-opensource#7184)

danmar · danmar · commit 1b0bb02f1dfa · 2015-11-30T11:12:51.000+01:00
diff --git a/lib/checkcondition.cpp b/lib/checkcondition.cpp
@@ -1030,12 +1030,15 @@ void CheckCondition::checkInvalidTestForOverflow()
                 continue;
 
             const Token *calcToken, *exprToken;
-            if (tok->str() == "<" && tok->astOperand1()->str() == "+") {
+            bool result;
+            if (Token::Match(tok, "<|>=") && tok->astOperand1()->str() == "+") {
                 calcToken = tok->astOperand1();
                 exprToken = tok->astOperand2();
-            } else if (tok->str() == ">" && tok->astOperand2()->str() == "+") {
+                result = (tok->str() == ">=");
+            } else if (Token::Match(tok, ">|<=") && tok->astOperand2()->str() == "+") {
                 calcToken = tok->astOperand2();
                 exprToken = tok->astOperand1();
+                result = (tok->str() == "<=");
             } else
                 continue;
 
@@ -1058,18 +1061,20 @@ void CheckCondition::checkInvalidTestForOverflow()
 
             // Only warn when termToken is always positive
             if (termToken->valueType() && termToken->valueType()->sign == ValueType::Sign::UNSIGNED)
-                invalidTestForOverflow(tok);
+                invalidTestForOverflow(tok, result);
             else if (termToken->isNumber() && MathLib::isPositive(termToken->str()))
-                invalidTestForOverflow(tok);
+                invalidTestForOverflow(tok, result);
         }
     }
 }
 
-void CheckCondition::invalidTestForOverflow(const Token* tok)
+void CheckCondition::invalidTestForOverflow(const Token* tok, bool result)
 {
     std::string errmsg;
     errmsg = "Invalid test for overflow '" +
              (tok ? tok->expressionString() : std::string("x + u < x")) +
-             "'. Condition is always false unless there is overflow, and overflow is UB.";
+             "'. Condition is always " +
+             std::string(result ? "true" : "false") +
+             " unless there is overflow, and overflow is UB.";
     reportError(tok, Severity::warning, "invalidTestForOverflow", errmsg);
 }
diff --git a/lib/checkcondition.h b/lib/checkcondition.h
@@ -126,7 +126,7 @@ class CPPCHECKLIB CheckCondition : public Check {
 
     void alwaysTrueFalseError(const Token *tok, bool knownResult);
 
-    void invalidTestForOverflow(const Token* tok);
+    void invalidTestForOverflow(const Token* tok, bool result);
 
     void getErrorMessages(ErrorLogger *errorLogger, const Settings *settings) const {
         CheckCondition c(0, settings, errorLogger);
@@ -142,7 +142,7 @@ class CPPCHECKLIB CheckCondition : public Check {
         c.moduloAlwaysTrueFalseError(0, "1");
         c.clarifyConditionError(0, true, false);
         c.alwaysTrueFalseError(0, true);
-        c.invalidTestForOverflow(0);
+        c.invalidTestForOverflow(0, false);
     }
 
     static std::string myName() {
diff --git a/test/testcondition.cpp b/test/testcondition.cpp
@@ -1613,6 +1613,21 @@ class TestCondition : public TestFixture {
               "}");
         ASSERT_EQUALS("[test.cpp:2]: (warning) Invalid test for overflow '(p+x)<p'. Condition is always false unless there is overflow, and overflow is UB.\n", errout.str());
 
+        check("void f(char *p, unsigned int x) {\n"
+              "    assert((p + x) >= p);\n"
+              "}");
+        ASSERT_EQUALS("[test.cpp:2]: (warning) Invalid test for overflow '(p+x)>=p'. Condition is always true unless there is overflow, and overflow is UB.\n", errout.str());
+
+        check("void f(char *p, unsigned int x) {\n"
+              "    assert(p > (p + x));\n"
+              "}");
+        ASSERT_EQUALS("[test.cpp:2]: (warning) Invalid test for overflow 'p>(p+x)'. Condition is always false unless there is overflow, and overflow is UB.\n", errout.str());
+
+        check("void f(char *p, unsigned int x) {\n"
+              "    assert(p <= (p + x));\n"
+              "}");
+        ASSERT_EQUALS("[test.cpp:2]: (warning) Invalid test for overflow 'p<=(p+x)'. Condition is always true unless there is overflow, and overflow is UB.\n", errout.str());
+
         check("void f(signed int x) {\n"
               "    assert(x + 100 < x);\n"
               "}");
