← Trexquant Interview Insights

Trexquant·Software Engineer·Recruiter / HR Screen·Intermediate

Intermediate
May 2026

Summary

Recruiter screen at Trexquant, pretty standard stuff on availability and role fit, but they threw in a C++ fundamentals question that I wasn't fully expecting at this stage.

Questions Asked (1)

Q1

What constructors and special member functions does a C++ class implicitly have by default?

Technical Trade-offs
Author's notes

Caught me slightly off guard on a recruiter call.

Create a free account to read the full note

AI HintsAI Generated

Suggested Approach

Start by listing the six special member functions that are implicitly declared by default: default constructor, destructor, copy constructor, copy assignment operator, move constructor, and move assignment operator. Then explain the conditions under which each is generated, suppressed, or deprecated, emphasizing the Rule of Zero/Five and the impact of user-declared special members.

Pro tip: Mention that the implicit move operations are only generated if no copy operations, destructor, or move operations are user-declared, and that the default constructor is not generated if any other constructor is user-declared. This shows deep understanding of the subtle rules.

1. List the six special member functions

Enumerate the default constructor, destructor, copy constructor, copy assignment operator, move constructor, and move assignment operator as the implicitly declared members.

2. Explain default generation rules

Describe that these are generated only if not user-declared, and note exceptions: default constructor not generated if any constructor is user-declared; move operations not generated if copy operations, destructor, or move operations are user-declared.

3. Discuss suppression and deprecation

Mention that some implicit members are defined as deleted (e.g., move operations when copy operations are user-declared) and that implicit copy operations are deprecated when a user-declared destructor or copy operation exists.

4. Connect to the Rule of Zero/Five

Explain how the default behavior aligns with the Rule of Zero (rely on implicit members) and Rule of Five (if you declare one, declare all five) to manage resources correctly.

5. Highlight practical implications

Summarize how these rules affect class design, performance (move semantics), and correctness (resource management, slicing, etc.).

Key Points to Mention

  • Default constructor: implicitly declared only if no user-declared constructors.
  • Destructor: implicitly declared, non-virtual unless base class has virtual destructor.
  • Copy constructor and copy assignment operator: implicitly declared, perform member-wise copy; deprecated if user-declared destructor or copy operation.
  • Move constructor and move assignment operator: implicitly declared only if no user-declared copy operations, destructor, or move operations; otherwise not declared or defined as deleted.
  • Rule of Zero/Five: design classes to either rely on implicit members or explicitly define all five (or six) special member functions.
  • Implicit members are public and inline; their generation can be suppressed by user-declaration or by certain member declarations (e.g., reference members delete copy assignment).

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.