Method checkInvalidTestForOverflow

lib/checkcondition.cpp:1690–1776

}

void CheckConditionImpl::checkInvalidTestForOverflow()
{
    // Interesting blogs:
    // https://www.airs.com/blog/archives/120
    // https://kristerw.blogspot.com/2016/02/how-undefined-signed-overflow-enables.html
    // https://research.checkpoint.com/2020/optout-compiler-undefined-behavior-optimizations/

    // x + c < x       ->   false
    // x + c <= x      ->   false
    // x + c > x       ->   true
    // x + c >= x      ->   true

    // x + y < x       ->   y < 0


    if (!mSettings.severity.isEnabled(Severity::warning))
        return;

    logChecker("CheckCondition::checkInvalidTestForOverflow"); // warning

    for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) {
        if (!Token::Match(tok, "<|<=|>=|>") || !tok->isBinaryOp())
            continue;

        const Token *lhsTokens[2] = {tok->astOperand1(), tok->astOperand2()};
        for (const Token *lhs: lhsTokens) {
            std::string cmp = tok->str();
            if (lhs == tok->astOperand2())
                cmp[0] = (cmp[0] == '<') ? '>' : '<';

            if (!Token::Match(lhs, "[+-]") || !lhs->isBinaryOp())
                continue;

            const bool isSignedInteger = lhs->valueType() && lhs->valueType()->isIntegral() && lhs->valueType()->sign == ValueType::Sign::SIGNED;
            const bool isPointer = lhs->valueType() && lhs->valueType()->pointer > 0;
            if (!isSignedInteger && !isPointer)
                continue;

            const Token *exprTokens[2] = {lhs->astOperand1(), lhs->astOperand2()};
            for (const Token *expr: exprTokens) {
                if (lhs->str() == "-" && expr == lhs->astOperand2())
                    continue; // TODO?

                if (expr->hasKnownIntValue())
                    continue;

                if (!isSameExpression(true,
                                      expr,
                                      lhs->astSibling(),
                                      mSettings,
                                      true,
                                      false))
                    continue;

                const Token * const other = expr->astSibling();

                // x [+-] c cmp x
                if ((other->isNumber() && other->hasKnownIntValue() && other->getKnownIntValue() > 0) ||