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Modern C++ Features

C++14 Features

Learn features introduced in the C++14 standard, refining C++11 capabilities.

Interview: Generic lambdas, return type deduction, and the introduction of std::make_unique.

Last Updated: June 13, 2026 • 8 min read

Released as a refinement standard, C++14 completes features introduced in C++11. Key features include generic lambdas, function return type deduction, and std::make_unique.

Generic Lambdas

Allows lambda parameters to be declared as auto, generating template function calls under the hood.

std::make_unique

Resolves an omission in C++11. Provides a safe way to instantiate std::unique_ptr without using the new operator.

Digit Separators

Use single quotes as digit separators (e.g. 1'000'000) to improve code readability.

The Import of std::make_unique

While C++11 introduced std::make_shared, it did not include std::make_unique. Using raw new statements can lead to memory leaks if exception propagation occurs during parameter evaluation:

Safety Rule

Always use std::make_unique to construct unique pointers. It guarantees exception safety and avoids raw new calls: auto ptr = std::make_unique<Widget>();

Code Walkthrough

Demonstrates generic lambdas, return type deduction, and binary literals in C++14. 

#include <iostream>
#include <memory>
#include <vector>

// C++14: Automatic return type deduction for functions
auto calculateSum(int a, int b) {
    return a + b; // Compiler deduces return type is int
}


int main() {
    // C++14: Binary literals and digit separators
    int mask = 0b1100'1010;
    long largeVal = 1'000'000'000L;


// C++14: Generic lambdas using auto parameters
    auto printVal = [](auto x) {
        std::cout << "Value: " << x << '\n';
    };


printVal(42);       // Deduces x as int
    printVal("Hello");  // Deduces x as const char*


// C++14: std::make_unique instantiation
    auto ptr = std::make_unique<std::vector<int>>();
    ptr->push_back(10);


std::cout << "Vector size: " << ptr->size() << '\n';
    return 0;
}

Interview-Relevant Information

Q: Why was std::make_unique missing from C++11?
Answer: Its omission was an oversight by the committee. std::make_shared was prioritized because it combines control blocks and object allocations into a single memory block, which is a key optimization. Since unique pointers do not use control blocks, std::make_unique was considered less urgent but was added in C++14 to standardize smart pointer creation.

Q: How do generic lambdas work under the hood?
Answer: The compiler translates the lambda into a functor class with a templated call operator: template<typename T> auto operator()(T x) const. This allows the lambda to accept any type.

Quick Checklist

Did you replace raw new smart pointer constructions with std::make_unique? Do you use generic lambdas? If yes, your code is C++14 compliant.

Use Cases

Replacing raw new/delete memory operations with smart pointers.

Writing reusable functional callbacks using generic lambdas.

Common Mistakes

Manually writing template classes when a generic lambda with auto parameters is simpler and cleaner.

Constructing std::unique_ptr instances using raw new, which can lead to memory leaks if constructor arguments throw exceptions.