Emscripten 和从 std::bind 到 std::function 的转换

Posted 2023-02-22

【中文标题】Emscripten 和从 std::bind 到 std::function 的转换

【英文标题】：Emscripten and conversion from std::bind to std::function

【发布时间】：2015-02-11 21:19:37

【问题描述】：

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

我将函数存储在这个：

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的成员函数：

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)
                                                    ^

我尝试将 CBFunction 切换到

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

到处都是，但它没有解决问题，我需要其他地方的 CBFunction。

emscripten 版本是 1.29.0，clang 3.4

【参考方案1】：

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

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

但您正试图将其转换为带有签名的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。