How do I approach Software Engineering Fundamentals interview questions?

Software Engineering Fundamentals questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master software engineering fundamentals interviews.

What difficulty level is this interview question?

This is a medium difficulty Software Engineering Fundamentals question, commonly asked during Onsite rounds at Trexquant.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at Trexquant during technical interviews.

Explain C++ default constructor generation rules

Last updated: Mar 29, 2026

Quick Overview

This question evaluates understanding of C++ special-member-function rules—specifically when the compiler implicitly declares a default constructor, when that implicitly-declared constructor is defined as deleted, and how user-declared copy/move constructors, copy/move assignments, destructors, and member/base types (const, reference, or non-default-constructible) affect generation. Commonly asked to assess mastery of language semantics and object-initialization pitfalls, it belongs to the Software Engineering Fundamentals domain and tests both conceptual understanding of compiler behavior and practical application in C++ code.

Trexquant

Sep 1, 2025, 12:00 AM

Software Engineer

Onsite

Software Engineering Fundamentals

You are given a C++ class type T.

When will the compiler implicitly declare a default constructor for T ?
When will the implicitly-declared default constructor be defined as deleted (i.e., T t; is ill-formed)?
How do user-declared special member functions (copy/move ctor, copy/move assignment, destructor) affect whether a default constructor is generated?
What changes if members/base classes have no default constructors, are references, or are const ?

Answer in terms of the C++ “special member functions” model (rule of 0/3/5) and include a few small examples of classes that:

get an implicit default constructor,
do not get one,
get one but it is deleted.

Solution

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