C++ Internals

Rule of Five Audit

Difficulty

Asked at DRW, Da Vinci Derivatives

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x xxxx xxxxxxx xxxxx xx xx-xxxxx xxxxxxxx (xxxxx xxxx xxxxxxxxxx, xxxxxx, xx xxxxxxxx xxxxxxx) xx xx xxxx xxxxx. xxx xxxxxxx xx xxxx xxxxxxx xx xxx xxxx xxxxxxx xxxxxx xxxxxxxxx xxxx xxx xxxxxxxx xxxxxxxxx xxxxx: xxxxxxx xxx xxxxx xx xxx xxxxx, xxxxxxx xxxxxxx xxxx, xxxxxxxxx xxxxx xxxxxxxxx.

xxxxxxxxx xxxxxxxxxx xxxx xxx xxxxxxxx xxxxxxxxxxxx xxxxxx xxx:

xxx xxxxxxx xxxxxxxxxxx xxxxxxxx x xxxxxx xxxx xxxx_x().
xxx xxxxxxxxxx xxxxxxxx xx xxxx xxxxx_x(xx), xxxxxxx xxxx, xxx xxxx xx xxx xxxxxx xxxxx xxxx x xxxxxx.
xxxx xxxxxxxxxxx xxx xxxx xxxxxxxxxx xxxx xxx xxxxxxx (xxxxxx xxxx): xxx xxxxxx xx xxx xxxxxx xxxxx xxxx x xxxxxx xxxxx.
xxx xxxx xxxxxxxxxxx xxxxxxxxx xxxxxxxxx xxx xxxxxx xxx xxxxxx xxxxx (xxxxx() == xxxxx, xx() == -x), xxxxxxx xxxxxxx.
xxxx xxxxxxxxxx xxxxx xxxxxx xxx xxx xxxxxx (xx xxx), xxxx xxxxx xxx xxxxxx'x. x = xxx::xxxx(x) xxxx xxxxx x xxxxxxxxx.
xxxx xxxx xxxxxxxxxx xxxx xx xxxxxxxx. xxxx xx xxx x xxxxx xxxxx: xxx::xxxxxx xxxx xxxxx xxxxxxxx xxxxxx xxxxxxxxxxxx xxxx xxx xxxx xxxxxxxxxxx xx xxxxxxxx (xxxxxxxxx xx xxxxxx xxx xxx xxxxxx xxxxxxxxx xxxxxxxxx), xxx x xxxxxx xxxx xxxxxx xxx::xx_xxxxxxx_xxxx_xxxxxxxxxxxxx_x<xxxxxxxxxx>.
xxxx xx() xxx xxxxx() xx xxxxx; xx xxxxx xxxxxx xx xxxxxxxxxxx xx -x.

xxx xxxxxxxxxxxxxxx xxxxxx xxxxx(), xxxxxx() xxx xxx_xxxxxx() (x xxxxx xx xxxxxxxxx xxx xxxxxxxxx xxxx, xxxxxxxxx -x). xxxxxxx xxxx xxxxx xxxxxxxx x xxx xxxxx, xxx xxxxx xxxx xx xxxxxxx xx xxxxxxx xxx xxxxx xx xxx xxxx xxx xxxxx xxxx xxx xx xxxxx.

xxxxxxxx

[]{ xxxxx_xxxxxxxx(); { xxxxxxxxxx x; xxxxxxxxxx x; } xxxxxx xxx::xxxxx<xxxx xxxx, xxxx xxxx, xxxx xxxx>(xxxxx(), xxxxxx(), xxx_xxxxxx()); }()
// (x, x, x)  (xxx xxxxxxx xxxxxx, xxx xxxxxx, xx xxxxxx xxxxxx)

[]{ xxxxx_xxxxxxxx(); xxx::xxxxxx<xxxx xxxx> xxx; { xxxxxxxxxx x; xxx xxxxxxxx = x.xx(); xxxxxxxxxx x = xxx::xxxx(x); xxx.xxxx_xxxx(x.xx() == xxxxxxxx ? x : x); xxx.xxxx_xxxx(x.xxxxx() ? x : x); xxx.xxxx_xxxx(xxxxxx()); } xxx.xxxx_xxxx(xxxxx()); xxx.xxxx_xxxx(xxxxxx()); xxx.xxxx_xxxx(xxx_xxxxxx()); xxxxxx xxx; }()
// [x, x, x, x, x, x]  (xxx xxxx xxxxxxxxx xxx xx, xxxxxxx xxx xxxxxx, xxxxxx xxxxxxx)

xxxxxxxxxxx

xx xxx xxxxxx xxx xxxxxxxxxxx xxxxxxxxxxxxxxx.
xxxxxxx xxx xxxxxxx xxxx xxxxxxx xxxx_x() / xxxxx_x().
xxxxxx xxxxx xxxxx xxxx xxxxxxxxxx, xxxx-xxxx, xxx x xxx::xxxxxx<xxxxxxxxxx> xxxxxxx xxxxxxxx xxxxxxxxxxxxx (xxx xxxxxxxx), xxxx xxxxx xxx xxxxxxxx xxx xxx xxxx xxxxxx.

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Language: C++FileHandle

#include <cstddef>
#include <vector>

// ...
// ...
// ...
// ...
// ...
// ...
// ...
// ...
// ...
// ...
// ...
namespace handlecheck {

inline std::vector<char>& states() { static std::vector<char> s; return s; }
inline long long& open_counter() { static long long c = 0; return c; }
inline long long& close_counter() { static long long c = 0; return c; }
inline long long& bad_close_counter() { static long long c = 0; return c; }

inline int open_h() {
    states().push_back(1);
    ++open_counter();
    return static_cast<int>(states().size()) - 1;
}

inline void close_h(int id) {
    if (id < 0 || id >= static_cast<int>(states().size()) || states()[static_cast<std::size_t>(id)] == 0) {
        ++bad_close_counter();
        return;
    }
    states()[static_cast<std::size_t>(id)] = 0;
    ++close_counter();
}

inline long long opens() { return open_counter(); }
inline long long closes() { return close_counter(); }
inline long long bad_closes() { return bad_close_counter(); }
inline void reset_counters() {
    open_counter() = 0;
    close_counter() = 0;
    bad_close_counter() = 0;
}

}  // ...

using handlecheck::bad_closes;
using handlecheck::close_h;
using handlecheck::closes;
using handlecheck::open_h;
using handlecheck::opens;
using handlecheck::reset_counters;

// ...
// ...
// ...
// ...
class FileHandle {
public:
    FileHandle() {
        // ...
    }

    ~FileHandle() {
        // ...
    }

    FileHandle(FileHandle&& other) {
        // ...
        (void)other;
    }

    FileHandle& operator=(FileHandle&& other) {
        // ...
        (void)other;
        return *this;
    }

    // ...

    int id() const { return handle_; }
    bool valid() const { return handle_ != -1; }

private:
    int handle_ = -1;
};

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