void FunctionArgsByValue::processFunction()

in src/checks/level2/function-args-by-value.cpp [107:204]
80 lines of code
31 McCabe index (conditional complexity)

void FunctionArgsByValue::processFunction(FunctionDecl *func)
{
    if (!func || !func->isThisDeclarationADefinition() || func->isDeleted()) {
        return;
    }

    if (func->isDefaulted()) {
        // The C++ compiler enforces refs or do being used for defaulted methods
        // https://invent.kde.org/sdk/clazy/-/issues/25
        return;
    }
    auto *ctor = dyn_cast<CXXConstructorDecl>(func);
    if (ctor && ctor->isCopyConstructor()) {
        return; // copy-ctor must take by ref
    }

    const bool warnForOverriddenMethods = isOptionSet("warn-for-overridden-methods");
    if (!warnForOverriddenMethods && Utils::methodOverrides(dyn_cast<CXXMethodDecl>(func))) {
        // When overriding you can't change the signature. You should fix the base classes first
        return;
    }

    if (shouldIgnoreOperator(func)) {
        return;
    }

    if (m_context->isQtDeveloper() && shouldIgnoreFunction(func)) {
        return;
    }

    Stmt *body = func->getBody();

    int i = -1;
    for (auto *param : Utils::functionParameters(func)) {
        i++;
        const QualType paramQt = clazy::unrefQualType(param->getType());
        const Type *paramType = paramQt.getTypePtrOrNull();
        if (!paramType || paramType->isIncompleteType() || paramType->isDependentType()) {
            continue;
        }

        if (shouldIgnoreClass(paramType->getAsCXXRecordDecl())) {
            continue;
        }

        clazy::QualTypeClassification classif;
        bool success = clazy::classifyQualType(m_context, param->getType(), param, classif, body);
        if (!success) {
            continue;
        }

        if (classif.passSmallTrivialByValue) {
            if (ctor) { // Implements fix for Bug #379342
                std::vector<CXXCtorInitializer *> initializers = Utils::ctorInitializer(ctor, param);
                bool found_by_ref_member_init = false;
                for (auto *initializer : initializers) {
                    if (!initializer->isMemberInitializer()) {
                        continue; // skip base class initializer
                    }
                    FieldDecl *field = initializer->getMember();
                    if (!field) {
                        continue;
                    }

                    QualType type = field->getType();
                    if (type.isNull() || type->isReferenceType()) {
                        found_by_ref_member_init = true;
                        break;
                    }
                }

                if (found_by_ref_member_init) {
                    continue;
                }
            }

            std::vector<FixItHint> fixits;
            auto *method = dyn_cast<CXXMethodDecl>(func);
            const bool isVirtualMethod = method && method->isVirtual();
            if (!isVirtualMethod || warnForOverriddenMethods) { // Don't try to fix virtual methods, as build can fail
                for (auto *redecl : func->redecls()) { // Fix in both header and .cpp
                    auto *fdecl = dyn_cast<FunctionDecl>(redecl);
                    const ParmVarDecl *param = fdecl->getParamDecl(i);
                    fixits.push_back(fixit(fdecl, param, classif));
                }
            }

            std::string paramStr = param->getType().getAsString(lo());

            if (const std::string paramName = param->getNameAsString(); !paramName.empty())
                paramStr.append(" " + paramName);

            std::string funcName = func->getQualifiedNameAsString();
            std::string error = funcName + ": Pass small and trivially-copyable type by value (" + paramStr + ')';
            emitWarning(param->getBeginLoc(), error, fixits);
        }
    }
}