C++基本异常问题

发布于 2024-11-26 21:13:35 字数 619 浏览 4 评论 0原文

有人可以描述一下处理以下情况的正确方法吗：

wchar_t* buffer = new wchar_t[...];

if (!something)
{
    throw std::runtime_error("Whatever");
    // Now, at this point I'm leaking memory allocated for the 'buffer'.
}

// Perform actions.
delete[] buffer;

解决该问题的明显方法意味着：

if (!something)
{
    delete[] buffer;
    throw std::runtime_error("Whatever");
}

现在 - 可以吗？ （我怀疑是这样，但谁知道呢:)

PS 我确实意识到有更好的方法来做到这一点 - 使用 boost::scoped_array 或简单地 std::wstring，它允许调用析构函数来释放分配的内存，只是出于好奇。

原文

Could someone please describe what's the correct way to handle the following situation:

wchar_t* buffer = new wchar_t[...];

if (!something)
{
    throw std::runtime_error("Whatever");
    // Now, at this point I'm leaking memory allocated for the 'buffer'.
}

// Perform actions.
delete[] buffer;

The obvious way to solve it means something like:

if (!something)
{
    delete[] buffer;
    throw std::runtime_error("Whatever");
}

Now - is it fine? (I suspect so, but who knows :)

P.S I do realize that there is a much better way to do it - using, boost::scoped_array or simply std::wstring, which allows the destructors called to release the allocated memory, just being curious.

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森末i 2024-12-03 21:13:35

你的见解是正确的。该模式

Acquire some resource
Do something
Release resource

从根本上来说是错误的，因为 Do Something 可能会引发异常并泄漏资源。此外，您必须记住释放资源，这是错误的丰富来源。

正如您所指出的，正确的方法是始终使用其析构函数释放资源的对象。其名称为 RAII。

这意味着例如。永远不要在析构函数之外使用delete，或者永远不要依赖手动关闭文件句柄，永远不要手动解锁互斥锁，等等。了解智能指针，并尽可能使用它们。

请注意，某些语言（非 C++）提供了finally 关键字，它允许您执行指令块，而不管是否引发异常。 C++ 使用 RAII，如果您编写正确的析构函数，您就不必担心资源释放。

我有一个用于 C++0x 的小实用程序，它允许在块退出时执行任意代码，如果您接口一次或两次编写质量较差的（或 C）库。

Your insight is right. The pattern

Acquire some resource
Do something
Release resource

is fundamentally wrong, since Do something can potentially throw an exception and leak the resource. Moreover, you have to remember to release the resource, which is a fertile source of errors.

The correct way, as you point, is to always use an object whose destructor releases the resource. This goes by the name of RAII in C++.

This means eg. never using delete outside destructors, or never rely on manually closing file handles, never unlock mutexes manually, etc. Learn about smart pointers, and use them whenever you can.

Note that some languages (not C++) provide a finally keyword, which permits you to execute a block of instructions irrespectively of whether an exception is thrown. C++ uses RAII, and you should never be concerned with resource release if you write proper destructors.

I have a little utility there for C++0x which allows execution of arbitrary code at block exit, should you interface once or twice with poorly written (or C) libraries.

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