[英]const pointer as std::bind parameter
The following code以下代码
#include <functional>
#include <iostream>
using namespace std;
struct TestStruct {
int c;
};
int f(int a, int b, const TestStruct **t) { return a + b + (*t)->c; }
void main() {
TestStruct *t;
bind(&f, 1, 2, &t)();
}
reports this error报告这个错误
error C2893: Failed to specialize function template 'unknown-type std::invoke(_Callable &&,_Types &&...)'
note: With the following template arguments:
note: '_Callable=int (__cdecl *&)(int,int,const TestStruct **)'
note: '_Types={int &, int &, TestStruct **&}'
It seems that the problem is the constness of the const TestStruct**
param.似乎问题在于
const TestStruct**
参数的const TestStruct**
。 However, there's no problem neither with const TestStruct *
nor with TestStruct**
.但是,
const TestStruct *
和TestStruct**
都没有问题。 Why ?为什么 ?
Your problem does not come from bind itself, but from the simple fact that casting T**
to T const**
is illegal.您的问题不是来自 bind 本身,而是来自将
T**
为T const**
是非法的简单事实。
see http://c-faq.com/ansi/constmismatch.html for an explanation as to why.有关原因的解释,请参见http://c-faq.com/ansi/constmismatch.html 。
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