c++ - Emscripten 和从 std::bind 到 std::function 的转换

Question

我正在尝试使用 emscripten 编译我的项目。在 Visual Studio 2013 中 native 一切正常。

我在这里存储函数:

template<typename Return, typename ...Arguments>
using CBFunction = std::function<Return(Arguments...)>;

typedef unsigned int CBID;

template<typename Return, typename ...Arguments>
class CBCollection
{
    std::map<CBID, CBFunction<Return, Arguments...>> cbs;
public:
    CBID addCB(CBFunction<Return, Arguments...> cb)
    {
        CBID id = findFreeID();
        cbs[id] = cb;
        return id;
    }

    ...
}

稍后我可以添加简单函数和成员函数:

CBCollection<void, MatrixStack, float> BeforeRenderCBs;
...
AnimatedSprite::AnimatedSprite()
{
    using namespace placeholders;
    BeforeRenderCBs.addCB(bind(&AnimatedSprite::beforeRenderCB, this, _1, _2));
}

使用 emscripten，结果如下:

<scratch space>:624:1: note: expanded from here
"C:/Development/LexUnitEngine/Engine/include/Buffer.h"
^
C:\Development\LexUnitEngine\Engine\source\AnimatedSprite.cpp:76:24: error: no viable conversion from '__bind<void (AnimatedSprite::*)(MatrixStack &, float), AnimatedSprite *, std::__1::placeholders::__ph<1> &, std::__1::placeholders::__ph<2> &>' to 'CBFunction<void, MatrixStack, float>'
      (aka 'std::__1::function<void (MatrixStack, float)>')
        BeforeRenderCBs.addCB(bind(&AnimatedSprite::beforeRenderCB, this, _1, _2));
                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\PROGRA~1\EMSCRI~1\EMSCRI~1\129~1.0\system\include\libcxx\functional:1448:5: note: candidate constructor not viable: no known conversion from '__bind<void (AnimatedSprite::*)(MatrixStack &, float), AnimatedSprite *, std::__1::placeholders::__ph<1> &, std::__1::placeholders::__ph<2> &>' to
      'nullptr_t' for 1st argument
    function(nullptr_t) _NOEXCEPT : __f_(0) {}
    ^
C:\PROGRA~1\EMSCRI~1\EMSCRI~1\129~1.0\system\include\libcxx\functional:1449:5: note: candidate constructor not viable: no known conversion from '__bind<void (AnimatedSprite::*)(MatrixStack &, float), AnimatedSprite *, std::__1::placeholders::__ph<1> &, std::__1::placeholders::__ph<2> &>' to
      'const std::__1::function<void (MatrixStack, float)> &' for 1st argument
    function(const function&);
    ^
C:\PROGRA~1\EMSCRI~1\EMSCRI~1\129~1.0\system\include\libcxx\functional:1450:5: note: candidate constructor not viable: no known conversion from '__bind<void (AnimatedSprite::*)(MatrixStack &, float), AnimatedSprite *, std::__1::placeholders::__ph<1> &, std::__1::placeholders::__ph<2> &>' to
      'std::__1::function<void (MatrixStack, float)> &&' for 1st argument
    function(function&&) _NOEXCEPT;
    ^
C:\PROGRA~1\EMSCRI~1\EMSCRI~1\129~1.0\system\include\libcxx\functional:1454:41: note: candidate template ignored: disabled by 'enable_if' [with _Fp = std::__1::__bind<void (AnimatedSprite::*)(MatrixStack &, float), AnimatedSprite *, std::__1::placeholders::__ph<1> &, std::__1::placeholders::__ph<2>
      &>]
                                        __callable<_Fp>::value &&
                                        ^
C:/Development/LexUnitEngine/Engine/include/CallbackCollection.h:49:46: note: passing argument to parameter 'cb' here
        CBID addCB(CBFunction<Return, Arguments...> cb)
                                                    ^

我试图将 CBFunction 切换为

std::function<Return(Arguments...)

无处不在，但它并没有解决问题，我需要在其他地方使用 CBFunction。

emscripten 版本为 1.29.0，clang 3.4

Answer 1

您的类型不匹配。如果查看编译错误，AnimatedSprite::beforeRenderCB 的类型为:

void (AnimatedSprite::*)(MatrixStack &, float)

但您正在尝试将其转换为具有签名的 std::function:

void(MatrixStack, float)

如果您将集合类型更改为:

CBCollection<void, MatrixStack&, float> BeforeRenderCBs;
//                            ^

它应该可以工作。