# Behavioral correctness (llmcpp)

**Behavioral correctness** means fulfilling the intended contract, not merely producing valid C++. The repository deliberately includes a request that compiler checks cannot establish:

```cpp
__llm__ std::string solve_riemann_hypothesis()
{
    Solve the Riemann hypothesis. Return the solution in the form of a string.
}
```

A body returning an arbitrary string could compile while failing this request completely. Acceptance checks types and language rules, not the truth of a mathematical claim.

For ordinary functions, make requirements testable: check expected results, state changes, empty inputs, duplicates, and failure paths as appropriate. Inspect [[llmcpp-generated-source-output|generated source]] for assumptions before preserving it in the cache. Regeneration or a changed contract calls for renewed review even when the replacement compiles on its first attempt.

Source: [04_impossible_request.cpp](https://github.com/yanevskiv/llmcpp/blob/main/examples/04_impossible_request.cpp).