c++ - STL vector 上的奇怪复制构造函数错误

Question

因此，我目前正在完成我的物理引擎，但我无法弄清楚某个类有什么问题，以及为什么编译器报告它的复制构造函数在使用 vector 时被删除了。

---

这是我的类(class)

const real baumgarteCoef = 0.5f;
// based on GoblinPhysics'
// https://github.com/chandlerprall/GoblinPhysics/blob/master/src/classes/Constraints/ContactConstraint.js
class ContactConstraint : public Constraint {
public:
    ContactConstraint(PhysicalObject* objA, PhysicalObject* objB, const Vector3& position,
                       const Vector3& normal, real penetration)
        : Constraint(objA, objB, (u32)1) {
        collisionPosition = position;
        collisionNormal = normal;
        this->penetration = penetration;
        real r1 = objA->getRestitution();
        real r2 = objB->getRestitution();
        restitutionCoef = Math::SquareRoot(r1 * r2);
        rows[0].lowerLimit = 0.f;
        rows[0].upperLimit = Math::PositiveInfinity;
        collisionPosA = objA->getInverseRotation().rotate(position - objA->getPosition() +
                                                          normal * penetration);
        collisionPosB = objB->getInverseRotation().rotate(position - objB->getPosition() -
                                                          normal * penetration);
    }

    ContactConstraint(const ContactConstraint& c) = default;

    void update(real timeElapsed) {
        auto& row = rows[0];

        if (objA->isStatic()) {
            row.jacobian[0] = 0.f;
            row.jacobian[1] = 0.f;
            row.jacobian[2] = 0.f;
            row.jacobian[3] = 0.f;
            row.jacobian[4] = 0.f;
            row.jacobian[5] = 0.f;
        } else {
            row.jacobian[0] = -collisionNormal.x();
            row.jacobian[1] = -collisionNormal.y();
            row.jacobian[2] = -collisionNormal.z();

            Vector3 v = collisionPosition - objA->getPosition();
            Vector3 v2 = v.cross(collisionNormal);
            row.jacobian[3] = -v2.x();
            row.jacobian[4] = -v2.y();
            row.jacobian[5] = -v2.z();
        }

        if (objB->isStatic()) {
            row.jacobian[6] = 0.f;
            row.jacobian[7] = 0.f;
            row.jacobian[8] = 0.f;
            row.jacobian[9] = 0.f;
            row.jacobian[10] = 0.f;
            row.jacobian[11] = 0.f;
        } else {
            row.jacobian[6] = collisionNormal.x();
            row.jacobian[7] = collisionNormal.y();
            row.jacobian[8] = collisionNormal.z();

            Vector3 v = collisionPosition - objB->getPosition();
            Vector3 v2 = v.cross(collisionNormal);
            row.jacobian[9] = v2.x();
            row.jacobian[10] = v2.y();
            row.jacobian[11] = v2.z();
        }

        // Apply penetration error.
        row.bias = baumgarteCoef * penetration / timeElapsed;
        // Apply restitution
        Vector3 velocity = objA->getLinearVelocity() +
                        collisionPosA.cross(objA->getAngularVelocity()) -
                        objB->getLinearVelocity() - collisionPosB.cross(objB->getAngularVelocity());
        real restitution = (collisionNormal.dot(velocity)) * restitutionCoef;
        row.bias += restitution;
    }

private:
    Vector3 collisionPosition;
    Vector3 collisionNormal;
    Vector3 collisionPosA;
    Vector3 collisionPosB;
    real penetration;
    real restitutionCoef;
};

---

及其父类

// based on GoblinPhysics'
// https://github.com/chandlerprall/GoblinPhysics/blob/master/src/classes/Constraints/ConstraintRow.js
class Constraint {
public:
    class Row {
    public:
        Constraint* parent;
        real jacobian[12];
        real derivedMass[12];
        real effectiveMass;
        real lowerLimit;
        real upperLimit;
        real bias;
        real multiplier;
        real multiplierCache;
        real eta;

        void computeDerivedMass();
        void computeEffectiveMass();
        void computeEta(real timeDelta);
    };

    Constraint(PhysicalObject* objectA, PhysicalObject* objectB, u32 numRows) {
        objA = objectA;
        objB = objectB;
        rows = std::make_unique<Row[]>(numRows);
        this->numRows = numRows;
        for (u32 i = 0; i < numRows; i++)
            rows[i].parent = this;
        breakingThreshold = 0.f;
        active = true;
    }

    Constraint(const Constraint& c) = default;
    PhysicalObject* objA;
    PhysicalObject* objB;
    std::unique_ptr<Row[]> rows;
    Vector3 lastImpulse;
    u32 numRows;
    real breakingThreshold;
    bool active;

    virtual void update(real timeElapsed) = 0;
};

---

错误(上帝保佑，因为编译器可以压缩它)

[  9%] Building CXX object src/CMakeFiles/kepler3d.dir/PhysicsEngine/PhysicsEngine.cpp.obj
In file included from D:/msys64/mingw64/include/c++/7.3.0/memory:64:0,
                 from D:/msys64/home/ferna/Kepler3D/src/Architecture/Command.h: ,
                 from D:/msys64/home/ferna/Kepler3D/src/Architecture/Architecture.h:3,
                 from D:/msys64/home/ferna/Kepler3D/src/PhysicsEngine/PhysicsEngine.cpp:2:
D:/msys64/mingw64/include/c++/7.3.0/bits/stl_construct.h: In instantiation of 'void std::_Construct(_T1*, _Args&& ...) [with _T1 = Kepler3D::ContactConstraint; _Args = {Kepler3D::ContactConstraint}]':
D:/msys64/mingw64/include/c++/7.3.0/bits/stl_uninitialized.h:83:18:   required from 'static _ForwardIterator std::__uninitialized_copy<_TrivialValueTypes>::__uninit_copy(_InputIterator, _InputIterator, _ForwardIterator) [with _InputIterator = std::move_iterator<Kepler3D::ContactConstraint*>; _ForwardIterator = Kepler3D::ContactConstraint*; bool _TrivialValueTypes = false]'
D:/msys64/mingw64/include/c++/7.3.0/bits/stl_uninitialized.h:134:15:   required from '_ForwardIterator std::uninitialized_copy(_InputIterator, _InputIterator, _ForwardIterator) [with _InputIterator = std::move_iterator<Kepler3D::ContactConstraint*>; _ForwardIterator = Kepler3D::ContactConstraint*]'
D:/msys64/mingw64/include/c++/7.3.0/bits/stl_uninitialized.h:289:37:   required from '_ForwardIterator std::__uninitialized_copy_a(_InputIterator, _InputIterator, _ForwardIterator, std::allocator<_Tp>&) [with _InputIterator = std::move_iterator<Kepler3D::ContactConstraint*>; _ForwardIterator = Kepler3D::ContactConstraint*; _Tp = Kepler3D::ContactConstraint]'
D:/msys64/mingw64/include/c++/7.3.0/bits/stl_uninitialized.h:311:2:   required from '_ForwardIterator std::__uninitialized_move_if_noexcept_a(_InputIterator, _InputIterator, _ForwardIterator, _Allocator&) [with _InputIterator = Kepler3D::ContactConstraint*; _ForwardIterator = Kepler3D::ContactConstraint*; _Allocator = std::allocator<Kepler3D::ContactConstraint>]'
D:/msys64/mingw64/include/c++/7.3.0/bits/vector.tcc:426:6:   required from 'void std::vector<_Tp, _Alloc>::_M_realloc_insert(std::vector<_Tp, _Alloc>::iterator, _Args&& ...) [with _Args = {Kepler3D::PhysicalObject*&, Kepler3D::PhysicalObject*&, const Kepler3D::Vector3&, const Kepler3D::Vector3&, float&}; _Tp = Kepler3D::ContactConstraint; _Alloc = std::allocator<Kepler3D::ContactConstraint>; std::vector<_Tp, _Alloc>::iterator = __gnu_cxx::__normal_iterator<Kepler3D::ContactConstraint*, std::vector<Kepler3D::ContactConstraint> >; typename std::_Vector_base<_Tp, _Alloc>::pointer = Kepler3D::ContactConstraint*]'
D:/msys64/mingw64/include/c++/7.3.0/bits/vector.tcc:105:21:   required from 'std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::emplace_back(_Args&& ...) [with _Args = {Kepler3D::PhysicalObject*&, Kepler3D::PhysicalObject*&, const Kepler3D::Vector3&, const Kepler3D::Vector3&, float&}; _Tp = Kepler3D::ContactConstraint; _Alloc = std::allocator<Kepler3D::ContactConstraint>; std::vector<_Tp, _Alloc>::reference = Kepler3D::ContactConstraint&]'
D:/msys64/home/ferna/Kepler3D/src/PhysicsEngine/Dynamics/ConstraintsManager.h:23:82:   required from here
D:/msys64/mingw64/include/c++/7.3.0/bits/stl_construct.h:75:7: error: use of deleted function 'Kepler3D::ContactConstraint::ContactConstraint(const Kepler3D::ContactConstraint&)'
     { ::new(static_cast<void*>(__p)) _T1(std::forward<_Args>(__args)...); }

---

我不确定父类上的唯一指针是否导致无法派生复制构造函数。我还想补充一点，在任何情况下我都不会直接复制类(仅放置)，但是，由于 vector 类的内部机制，复制是默认的。

---

此行导致 ConstraintsManager 中的错误

contactConstraints.emplace_back(objA, objB, position, normal, penetration);

Answer 1

无法复制包含 unique_ptr 的对象，因为该成员(即 rows)默认情况下不可复制。如果您需要复制，您必须提供自己的实现。

据我所知，通过查看错误跟踪，我认为您应该能够移动对象。您是否尝试提供默认移动构造函数？

Constraint(Constraint&& c) = default;

我认为它也需要是 noexcept。

我不确定是否可以复制和/或移动您的派生类，因为我没有 Vector3 的定义。

很明显，从错误跟踪中可以看出，您需要能够复制(或移动)项目，因为在 vector 已满时添加项目时可能需要调整其大小。

虽然，我相信在这个例子中你需要深拷贝，在某些情况下，你可以存储 shared_ptr 而不是 unique_ptr 然后你会有一个浅拷贝构造函数自动生成。

如果事实上，它也可能在这里工作，但您需要小心不要意外复制然后修改对象，而没有意识到数据在这些对象之间部分共享。