C++方法需要引用，不能让Cython提供引用

Question

我正在通过Cython将Python与一个名为子弹物理的C++库进行接口。我有相当多的工作，但有一个问题是困扰我。这里是一个在多个上下文中发生的问题的例子。

一个子物理.h文件声明了一个方法，我将其复制并合并到我的cdefs中，如下所示：

cdef cppclass btSliderConstraint:
    btSliderConstraint *btSliderConstraint(btRigidBody& rbA, btRigidBody& rbB, const btTransform& frameInA, const btTransform& frameInB, bool useLinearReferenceFrameA)

问题是如何在对此方法的Cython调用中指定rbA和rbB引用(& rbA和& rbB)。我有很多指向btRigidBody对象的指针，但是这个方法的声明要求参数是引用(除非我弄错了)。

如果我只想为btRigidBody和rbB提供指向rbB对象的指针，那么cython编译器就会抱怨(这是可以理解的)：

Error compiling Cython file:
------------------------------------------------------------
    cdef btRigidBody *b1
    cdef btRigidBody *b2
    # bs.bodies is an array of pointers to btRigidBody objects, nbi and ji1 are integer indices
    b1 = bs.bodies[nbi]
    b2 = bs.bodies[ji1]
    motor = new btSliderConstraint(b1, b2, tra, trb, 1);
                                        ^
------------------------------------------------------------

fun4.pyx:922:41: Cannot assign type 'btRigidBody *' to 'btRigidBody'

我试图施放或取消尊重等人都没有做过这项工作。在普通的C++中，这似乎很容易做到，但在Cython中，我尝试过的任何东西似乎都不起作用。

如果我能够简单地声明一个类型为btRigidBody的变量，如下所示：

btRigidBody rbA

然后，我相信我可以把它作为一个论点来传递，编译器不会抱怨。我这样做是在其他情况下，它是有效的。但是，我不想在这里这样做，因为我已经有了指向要作为参数传递的对象的指针，而且，这样做还需要为btRigidBody对象存在一个“空构造函数”，并且库不提供不带参数的构造函数，而且出于可维护性的原因，我不想对库进行修改。

那么，如何在Cython中将指针转换为我所拥有的btRigidBody对象，转换为我需要的btRigidBody引用？

编辑：

使用*来取消引用指针在Cython中是行不通的(虽然我认为它在C++中会起作用)。在Cython中，会产生一系列令人困惑的错误：

Error compiling Cython file:
------------------------------------------------------------
...
    cdef btRigidBody *b1
    cdef btRigidBody *b2
    # bs.bodies is an array of pointers to btRigidBody objects, nbi and ji1 are integer indices
    b1 = bs.bodies[nbi]
    b2 = bs.bodies[ji1]
    motor = new btSliderConstraint(*b1, *b2, tra, trb, 1);
                                 ^
------------------------------------------------------------

fun4.pyx:922:34: Non-trivial keyword arguments and starred arguments not allowed in cdef functions.

Error compiling Cython file:
------------------------------------------------------------
...
    cdef btRigidBody *b1
    cdef btRigidBody *b2
    # bs.bodies is an array of pointers to btRigidBody objects, nbi and ji1 are integer indices
    b1 = bs.bodies[nbi]
    b2 = bs.bodies[ji1]
    motor = new btSliderConstraint(*b1, *b2, tra, trb, 1);
                                     ^
------------------------------------------------------------

fun4.pyx:922:38: Cannot convert 'btRigidBody *' to Python object

Error compiling Cython file:
------------------------------------------------------------
...
    cdef btRigidBody *b1
    cdef btRigidBody *b2
    # bs.bodies is an array of pointers to btRigidBody objects, nbi and ji1 are integer indices
    b1 = bs.bodies[nbi]
    b2 = bs.bodies[ji1]
    motor = new btSliderConstraint(*b1, *b2, tra, trb, 1);
                                          ^
------------------------------------------------------------

fun4.pyx:922:43: Cannot convert 'btRigidBody *' to Python object

Error compiling Cython file:
------------------------------------------------------------
...
    cdef btRigidBody *b1
    cdef btRigidBody *b2
    # bs.bodies is an array of pointers to btRigidBody objects, nbi and ji1 are integer indices
    b1 = bs.bodies[nbi]
    b2 = bs.bodies[ji1]
    motor = new btSliderConstraint(*b1, *b2, tra, trb, 1);
                                               ^
------------------------------------------------------------

fun4.pyx:922:48: Cannot convert 'btTransform' to Python object

Error compiling Cython file:
------------------------------------------------------------
...
    cdef btRigidBody *b1
    cdef btRigidBody *b2
    # bs.bodies is an array of pointers to btRigidBody objects, nbi and ji1 are integer indices
    b1 = bs.bodies[nbi]
    b2 = bs.bodies[ji1]
    motor = new btSliderConstraint(*b1, *b2, tra, trb, 1);
                                                    ^
------------------------------------------------------------

fun4.pyx:922:53: Cannot convert 'btTransform' to Python object

Error compiling Cython file:
------------------------------------------------------------
...
    cdef btRigidBody *b1
    cdef btRigidBody *b2
    # bs.bodies is an array of pointers to btRigidBody objects, nbi and ji1 are integer indices
    b1 = bs.bodies[nbi]
    b2 = bs.bodies[ji1]
    motor = new btSliderConstraint(*b1, *b2, tra, trb, 1);
                                 ^
------------------------------------------------------------

fun4.pyx:922:34: Cannot convert Python object to 'btSliderConstraint *'

Error compiling Cython file:
------------------------------------------------------------
...
    cdef btRigidBody *b1
    cdef btRigidBody *b2
    # bs.bodies is an array of pointers to btRigidBody objects, nbi and ji1 are integer indices
    b1 = bs.bodies[nbi]
    b2 = bs.bodies[ji1]
    motor = new btSliderConstraint(*b1, *b2, tra, trb, 1);
                                 ^
------------------------------------------------------------

fun4.pyx:922:34: Storing unsafe C derivative of temporary Python reference

Answer 1

由于Cython的目标是保持Python语法，所以不可能使用*作为指针取消引用。相反，使用[]。以下是所希望的：

运动=新btSliderConstraint(bs.bodiesnbi，bs.bodiesji1，tra，trb，1)；