C++ interview questions and answers

Stack objects die when the scope ends and are fast.

I mark methods and params const when they should not modify state.

Releasing resources the object owns when it goes out of scope.

A race happens when two threads use shared data without proper synchronization and the result depends on timing.

vector is dynamic size on the heap

CPUs fetch memory in cache lines.

A null-terminated const char pointer for C APIs.

Prefer types whose members manage themselves so you write no special destructor or copy ops.

A declaration introduces a name

Documenting invariants in debug builds that abort on violation.

Exclusive ownership of a heap object that deletes on destruction.

Atomic refcount updates add overhead and can bounce cache lines.

It casts to an rvalue so move constructors can steal resources.

In templates it preserves value category when passing arguments onward.

map keeps keys ordered and has stable iterators references more often

Reallocation invalidates all iterators and references.

I check has_value or use value_or before value().

A data race is concurrent conflicting access without sync — UB in C++.

Mutual exclusion around a critical section sharing state.

Threads wait until a predicate becomes true and get notified.