SKILL.md
C++ Error Handling
Core Question
Is this error recoverable?
- Yes (Local):
std::expectedor return code. - Yes (Distant): Exceptions (
throw). - No (Bug):
assertorstd::terminate.
Error → Design Question
| Issue | Design Question |
|---|---|
| Uncaught Exception | Did you forget to catch, or throw in noexcept? |
| Silent Failure | Did you ignore a return code? (Use [[nodiscard]]). |
| Destructor Throw | Never throw from destructor (std::terminate). |
Thinking Prompt
- Is absence valid?
- Yes? → std::optional<T>.
- Does caller need details?
- Yes? → std::expected<T, E> or Exception. - No? → bool or std::optional.
- Is it a Logic Error (Bug)?
- Yes? → assert() or std::terminate(). Do not throw for bugs in C++ (Contract Violation).
Trace Up / Down
- Trace Up:
- Issue: "Program aborted with 'terminate called recursively'." - Cause: An exception was thrown while stack unwinding (in a destructor). - Fix: Fix the destructor. Ensure RAII cleanup is noexcept.
Quick Reference
| Mechanism | Cost (Happy) | Cost (Sad) | Use When |
|---|---|---|---|
std::optional |
Branch | Branch | Return may be empty. |
std::expected |
Branch | Branch | Recoverable error (Parsing). |
| Exception | Zero | Huge | Rare IO/Resource errors. |
| Assert | Zero (Release) | Abort | Logic bugs / Invariants. |