type_info，vtable [英] type_info, vtable

问题描述

什么是type_info函数，更具体地说，什么是type_info节点？

这些是否与vtable有关？

我看过链接器错误如此as：

对SomeClass type_info节点的未定义引用或者

对SomeClass type_info函数的未定义引用


这究竟意味着什么？什么是链接器寻找？


谢谢。

解决方案

" sks_cpp" < SK ***** @ hotmail.com>在留言中写道

新闻：Nn ******************* @ news2.central.cox.net ..

|什么是type_info函数，更具体地说，什么是type_info节点？

|这些与vtable有什么关系吗？


有点儿。在几个实现中，vtable存储了type_info数据结构的地址

。

这个数据结构用于实现运行时类型识别

（RTTI），

a功能，它是异常处理，dynamic_cast调用，
和typeid运算符的实现所必需的（参见header< typeinfo>）。 />

|我见过链接器错误，例如：

| 对SomeClass type_info节点的未定义引用或者

| 对SomeClass type_info函数的未定义引用


某些C ++编译器实现允许为RTTI启用/禁用支持

。您可能需要为某些文件启用它...

hth

-

Ivan Vecerina<> http://www.post1.com/~ivec

Brainbench MVP for C ++<> http://www.brainbench.com

Ivan Vecerina写道：

这个数据结构用于实现运行时类型识别
（RTTI），一个功能这是异常处理所必需的，

RTTI不需要进行异常处理，也不足够。

Rolf Magnus < RA ****** @ t-online.de>在消息中写道

新闻：bh ************* @ news.t-online.com ...

| Ivan Vecerina写道：

|

| >此数据结构用于实现运行时类型标识

| > （RTTI），异常处理所需的功能，

|

| RTTI不需要进行异常处理，也不足够。


我没有声称它已经足够了。


但是RTTI需要匹配捕获处理程序和异常。

考虑：


#include< vector>

#include< string> ;

#include< iostream>

#include< exception>

int main（）

{

尝试{

std :: vector< std :: string> tooBig（1UL<<< 31，只是一些字符串）;

}

catch（std :: exception& x）{

std :: cerr<< 失败：<<< x.what（）<< std :: endl;

}

}


C ++运行时如何处理此内存分配失败

没有RTTI？

问候，

Ivan

-
http://www.post1.com / ~vevec

What is a type_info function, more particularly, what is a type_info node?
Are these related to the vtable by any means?
I have seen linker errors such as:
"undefined reference to SomeClass type_info node" or
"undefined reference to SomeClass type_info function"

What does that really mean? What is the linker looking for?

Thanks.

解决方案

"sks_cpp" <sk*****@hotmail.com> wrote in message
news:Nn*******************@news2.central.cox.net.. .
| What is a type_info function, more particularly, what is a type_info node?
| Are these related to the vtable by any means?

Somewhat. In several implementations, the vtable stores the address of
the type_info data structure.
This data structure is used to implement Run-Time Type Identification
(RTTI),
a feature which is required for exception handling, dynamic_cast calls,
and the implementation of the typeid operator (see header <typeinfo>).

| I have seen linker errors such as:
| "undefined reference to SomeClass type_info node" or
| "undefined reference to SomeClass type_info function"

Some C++ compiler implementations allow to enable/disable support
for RTTI. You probably need to enable it for some files...
hth
--
Ivan Vecerina <> http://www.post1.com/~ivec
Brainbench MVP for C++ <> http://www.brainbench.com

Ivan Vecerina wrote:

This data structure is used to implement Run-Time Type Identification
(RTTI), a feature which is required for exception handling,

RTTI isn''t need for exception handling, neither would it be sufficient.

"Rolf Magnus" <ra******@t-online.de> wrote in message
news:bh*************@news.t-online.com...
| Ivan Vecerina wrote:
|
| > This data structure is used to implement Run-Time Type Identification
| > (RTTI), a feature which is required for exception handling,
|
| RTTI isn''t need for exception handling, neither would it be sufficient.

I did not claim it was sufficient.

But RTTI is needed to match catch handlers with exceptions.
Consider:

#include <vector>
#include <string>
#include <iostream>
#include <exception>
int main()
{
try {
std::vector<std::string> tooBig(1UL<<31,"just some string");
}
catch(std::exception& x) {
std::cerr << "Failure: "<<x.what()<<std::endl;
}
}

How would the C++ run-time handle a failure of this memory allocation
without RTTI?
Regards,
Ivan
--
http://www.post1.com/~ivec

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