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Warning C26473

  • Artikkeli

Don't cast between pointer types where the source type and the target type are the same.

C++ Core Guidelines: Type.1: Avoid casts

This rule helps to remove unnecessary or suspicious casts. Obviously, when a type is converted to itself, such a conversion is ineffective. Yet the fact that the cast is used may indicate a subtle design issue or a potential for regression if types change in future. It's always safer to use as few casts as possible.

Remarks

  • This rule is implemented for static casts and reinterpret casts, and checks only pointer types.

Example

dangerously generic lookup

gsl::span<server> servers_;

template<class T>
server* resolve_server(T tag) noexcept {
    auto p = reinterpret_cast<server*>(tag); // C26473, also 26490 NO_REINTERPRET_CAST
    return p >= &(*servers_.begin()) && p < &(*servers_.end()) ? p : nullptr;
}

void promote(server *s, int index) noexcept {
    auto s0 = resolve_server(s);
    auto s1 = resolve_server(index);
   if (s0 && s1)
        std::swap(s0, s1);
}

dangerously generic lookup - reworked

// ...
server* resolve_server(server *p) noexcept {
    return p >= &(*servers_.begin()) && p < &(*servers_.end()) ? p : nullptr;
}

server* resolve_server(ptrdiff_t i) noexcept {
    return !servers_.empty() && i >= 0 && i < servers_.size() ? &servers_[i] : nullptr;
}
// ...