Fixed #5885 - fsanitize=undefined: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int' in lib/tokenize.cpp.

lib/mathlib.cpp

@@ -539,6 +539,18 @@ std::string MathLib::subtract(const std::string &first, const std::string &secon
     return toString(d1 - d2);
 }
 
+std::string MathLib::incdec(const std::string & var, const std::string & op)
+{
+    if (op == "++")
+        return MathLib::add(var, "1");
+    else if (op == "--")
+        return MathLib::subtract(var, "1");
+
+    throw InternalError(0, std::string("Unexpected operation '") + op + "' in MathLib::incdec(). Please report this to Cppcheck developers.");
+    return "";
+
+}
+
 std::string MathLib::divide(const std::string &first, const std::string &second)
 {
     if (MathLib::isInt(first) && MathLib::isInt(second)) {

lib/mathlib.h

@@ -62,6 +62,7 @@ public:
     static std::string multiply(const std::string & first, const std::string & second);
     static std::string divide(const std::string & first, const std::string & second);
     static std::string mod(const std::string & first, const std::string & second);
+    static std::string incdec(const std::string & var, const std::string & op);
     static std::string calculate(const std::string & first, const std::string & second, char action);
 
     static std::string sin(const std::string & tok);

lib/tokenize.cpp

@@ -5198,21 +5198,6 @@ bool Tokenizer::simplifyFunctionReturn()
     return ret;
 }
 
-
-static void incdec(std::string &value, const std::string &op)
-{
-    int ivalue = 0;
-    std::istringstream istr(value);
-    istr >> ivalue;
-    if (op == "++")
-        ++ivalue;
-    else if (op == "--")
-        --ivalue;
-    std::ostringstream ostr;
-    ostr << ivalue;
-    value = ostr.str();
-}
-
 void Tokenizer::simplifyVarDecl(bool only_k_r_fpar)
 {
     simplifyVarDecl(list.front(), nullptr, only_k_r_fpar);
@@ -6918,7 +6903,7 @@ bool Tokenizer::simplifyKnownVariablesSimplify(Token **tok2, Token *tok3, unsign
                 tok3->varId(valueVarId);
                 tok3->deleteNext();
             }
-            incdec(value, op);
+            value = MathLib::incdec(value, op);
             if (!Token::simpleMatch((*tok2)->tokAt(-2), "for (")) {
                 (*tok2)->tokAt(2)->str(value);
                 (*tok2)->tokAt(2)->varId(valueVarId);
@@ -6928,7 +6913,7 @@ bool Tokenizer::simplifyKnownVariablesSimplify(Token **tok2, Token *tok3, unsign
 
         if (indentlevel == indentlevel3 && Token::Match(tok3->next(), "++|-- %varid%", varid) && MathLib::isInt(value) &&
             !Token::Match(tok3->tokAt(3), "[.[]")) {
-            incdec(value, tok3->next()->str());
+            value = MathLib::incdec(value, tok3->next()->str());
             (*tok2)->tokAt(2)->str(value);
             (*tok2)->tokAt(2)->varId(valueVarId);
             if (Token::Match(tok3, "[;{}] %any% %any% ;")) {

test/testmathlib.cpp

@@ -47,6 +47,7 @@ private:
         TEST_CASE(convert);
         TEST_CASE(naninf);
         TEST_CASE(isNullValue);
+        TEST_CASE(incdec);
     }
 
     void isGreater() const {
@@ -781,6 +782,25 @@ private:
         ASSERT_EQUALS(false, MathLib::isNullValue("garbage"));
         ASSERT_EQUALS(false, MathLib::isNullValue("UL"));
     }
+
+    void incdec() {
+        // increment
+        {
+            MathLib::biguint num = ~10U;
+            const std::string op = "++";
+            const std::string strNum = MathLib::incdec(MathLib::toString(num), op);
+            const MathLib::biguint incrementedNum = MathLib::toULongNumber(strNum);
+            ASSERT_EQUALS(num + 1U, incrementedNum);
+        }
+        // decrement
+        {
+            MathLib::biguint num = ~10U;
+            const std::string op = "--";
+            const std::string strNum = MathLib::incdec(MathLib::toString(num), op);
+            const MathLib::biguint decrementedNum = MathLib::toULongNumber(strNum);
+            ASSERT_EQUALS(num - 1U, decrementedNum);
+        }
+    }
 };
 
 REGISTER_TEST(TestMathLib)