放置新的和例外 [英] placement new and exception

问题描述

在 http：//www.parashift。 com / c ++ - faq-lit ... tore-mgmt.html

in [16.9]在p = new Fred（）中，Fred内存是否泄漏如果Fred

构造函数抛出异常？

有这段代码：


//原始代码：Fred * p =新Fred（）;

Fred * p =（Fred *）operator new（sizeof（Fred））;

尝试{

new（ p）Fred（）; //安置新

} catch（...）{

operator delete（p）; //释放内存

throw; //重新抛出异常

}


可以放置新的什么异常???

On http://www.parashift.com/c++-faq-lit...tore-mgmt.html
in [16.9] In p = new Fred(), does the Fred memory "leak" if the Fred
constructor throws an exception?
there is this code:

// Original code: Fred* p = new Fred();
Fred* p = (Fred*) operator new(sizeof(Fred));
try {
new(p) Fred(); // Placement new
} catch (...) {
operator delete(p); // Deallocate the memory
throw; // Re-throw the exception
}

What exception can placement new throw???

推荐答案

" wijhierbeneden"写道：

"wijhierbeneden" wrote:

什么异常可以放置新抛出???

What exception can placement new throw???

构造函数抛出的那些。


/ Pavel

Those thrown by constructor.

/Pavel

Fred * p =（Fred *）operator new（sizeof（Fred））;

Fred* p = (Fred*) operator new(sizeof(Fred));

我不认识上面的语法。


怎么样 ：


Fred * p = reinterpret_cast< Fred * const&>（new char [sizeof（Fred）]）;

I don''t recognize the syntax above.

How about:

Fred* p = reinterpret_cast<Fred* const &>( new char[sizeof(Fred)] );

JKop写道：

JKop wrote:

Fred * p =（Fred *）operator new（sizeof（Fred））;

Fred* p = (Fred*) operator new(sizeof(Fred));

我不认识上面的语法。

怎么样：

Fred * p = reinterpret_cast< Fred * const&>（new char [sizeof（Fred）]）;

I don''t recognize the syntax above.

How about:

Fred* p = reinterpret_cast<Fred* const &>( new char[sizeof(Fred)] );

它可以使用重载的运算符函数并访问它

直接。例如：


myclass& operator +（myclass& a，myclass& b）

{

} < br $>

....

....

myclass yy，zz，ss;


ss = operator +（yy，zz）;


与以下内容相同：


ss = yy + zz;


在极少数情况下这很有用......


David

it is valid to take an overloaded operator function, and access it
directly. For example:

myclass &operator +(myclass &a, myclass &b)
{
}

....
....
myclass yy,zz ,ss;

ss = operator +(yy,zz) ;

is the same as:

ss = yy + zz ;

in rare circumstances this is useful...

David

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