Executing bound std::function throws std::bad_function_call

问题

I want to bind a member function to a std::function<void(void)>. I heard that member functions take one extra parameter which is the instance pointer. Therefore I call std::bind(&Class::Function, this, parameter) but when I execute the function object, it throws a runtime error.

Unhandled exception at at 0x748D4B32 in Application.exe: Microsoft C++ exception: std::bad_function_call at memory location 0x0114F4E8.

The parameter is a pointer to one of my own structs. How am I doing wrong? What additional information do you need?

Update: Here is my code.

class ModuleRenderer
{
    struct Pass{ std::function<void()> Function; /* many more members... */ };
    std::vector<std::pair<std::string, Pass>> passes;

    enum Drawfunc{ FORMS, SKY, LIGHTS, QUAD, SCREEN };
    void AddPass(std::string Name, Drawfunc Function)
    {
        Pass pass;
        // set some of the members
        // ...

        passes.push_back(std::make_pair(Name, pass));
        Pass *pointer = &(passes.back().second);

        switch (Function)
        {
        case FORMS:
            pointer->Function = std::bind(&ModuleRenderer::DrawForms, this, pointer);
            break;

            // analogeously for the other cases
            // ...
        }
    }

    void DrawForms(Pass *pass)
    {
        // ...
    }

    // is called consecutively after adding all passes
    void Update()
    {
        for(auto i : passes)
            // some initializing based on members of pass
            i.Function();
    }
};

回答1:

A couple of different issues have been pointed out in the comments above. To resolve these, try making the following changes to your code:

struct Pass{ std::function<void(Pass *)> Function; /* ... */ };

// ...

case FORMS:
  pointer->Function = 
      std::bind(&ModuleRenderer::DrawForms, this, std::placeholders::_1);
  break;

Do not bind the Pass * to the function call just yet, because, as @molbdnilo points out, that pointer will become invalid when you call AddPass() multiple times and the vector is resized.

Since the std::function now takes a Pass *, you need to supply the correct pointer when you invoke it.

void Update()
{
    for(auto& i : passes) { // <-- take a reference, don't copy
        // some initializing based on members of pass
        i.Function( &i );   // pass Pass * to the function
}

回答2:

passes.push_back(std::make_pair(Name, pass));
Pass *pointer = &(passes.back().second);

That pointer will become invalid when you later push_back and the vector grows.

You could avoid pointers altogether and pass the index of the corresponding object instead of a pointer.

pointer->Function = std::bind(&ModuleRenderer::DrawForms, this, passes.size() - 1);

// ...

void DrawForms(size_t i)
{
    Pass& pass = passes[i].second;
    // Handle as before...
}

来源：https://stackoverflow.com/questions/17200804/executing-bound-stdfunction-throws-stdbad-function-call

标签

c++

runtime-error

function-calls

std-function

stdbind