不能继承auto_ptr没有问题 [英] Can't inherit from auto_ptr without problems
问题描述
我想做的是:
#include< memory>
class autostr:public std :: auto_ptr< char>
{
public:
autostr(char * a):std :: auto_ptr< char>(a){}
autostr(autostr& a):std :: auto_ptr< ; char>(a){}
//定义一组字符串utils here ...
};
autostr test(char a)
{
return autostr(new char(a));
}
void main(int args,char ** arg)
{
autostr asd = test('b');
return 0;
}
(我实际上有一个auto_ptr类的副本处理数组,但同样的错误适用于stl一个)
使用GCC 4.3.0的编译错误是:
main.cpp:152:错误:没有匹配的函数调用`autostr :: autostr(autostr)'
main.cpp:147:注意:候选人是:autostr :: autostr $ b main.cpp:146:注意:autostr :: autostr(char *)
我不明白为什么它不匹配autostr参数 c> 从函数返回的是一个临时的。临时值只能绑定到references-to-const( const autostr&
),但是你的引用是非const。 (和正确的。)
这是一个可怕的想法,几乎没有一个标准库打算继承。我已经在您的代码中看到一个错误:
autostrs(请不要删除我... oops
std :: string
有什么问题?
What I want to do is this:
#include <memory>
class autostr : public std::auto_ptr<char>
{
public:
autostr(char *a) : std::auto_ptr<char>(a) {}
autostr(autostr &a) : std::auto_ptr<char>(a) {}
// define a bunch of string utils here...
};
autostr test(char a)
{
return autostr(new char(a));
}
void main(int args, char **arg)
{
autostr asd = test('b');
return 0;
}
(I actually have a copy of the auto_ptr class that handles arrays as well, but the same error applies to the stl one)
The compile error using GCC 4.3.0 is:
main.cpp:152: error: no matching function for call to `autostr::autostr(autostr)' main.cpp:147: note: candidates are: autostr::autostr(autostr&) main.cpp:146: note: autostr::autostr(char*)
I don't understand why it's not matching the autostr argument as a valid parameter to autostr(autostr&).
The autostr
that is returned from the function is a temporary. Temporary values can only be bound to references-to-const (const autostr&
), but your reference is non-const. (And "rightly so".)
This is a terrible idea, almost none of the standard library is intended to be inherited from. I already see a bug in your code:
autostr s("please don't delete me...oops");
What's wrong with std::string
?
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