C++ interview questions and answers

Malloc is C, no constructors, returns void pointer.

Substitution failure is not an error: a bad template candidate is dropped instead of failing the whole program.

Two threads access the same memory, at least one writes, with no happens-before.

A function or variable can be defined only once in the program, with exceptions for inline and templates.

Sequential vector access beats pointer chasing in a list or tree.

If I need a CRUD web app and a GC, C# is faster to ship.

vector is contiguous, cache-friendly, and great for random access.

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

CPUs fetch memory in cache lines.

co_await suspension points let you write async logic linearly with compiler-generated state machines.

Use atomic pointers with careful memory orders and ABA mitigation like tagged pointers or hazard pointers.

They synchronize producer writes with consumer reads without full sequential consistency.

They constrain templates with readable requirements so failures are earlier and clearer.

AddressSanitizer catches many cases in tests.

Bump allocation for many short-lived objects freed at once.

Prefer contiguous data, structure-of-arrays when scanning one field, and avoid pointer chasing.

It is a space-optimized specialization without real bool references.

Different CRTs and exception personality routines may not match.

Precompiled headers, fewer includes via forward declares, unity builds carefully, and caching like ccache.

It returns a value or an error without exceptions for expected failures.