C ++变量声明被视为函数声明 [英] C++ variable declaration is treated like a function declaration

问题描述

这个问题是理论上的，尽管很有趣，是什么使MS VS2010将以下变量声明(在 main 内部)视为函数声明:

The question is fairly theoretical, though it's interesting what makes MS VS2010 treat the following variable declaration (inside main) like a function declaration:

typedef std::shared_ptr<asymm::PrivateKey> PrivateKeyPtr;

...
void main()
{
    ...
    maidsafe::dht::PrivateKeyPtr pk(); // I'm trying to init variable here, though it thinks it's function declaration

    kNode->node()->Store(key, value, "", ttl, pk, std::bind(&StoreCallback, args::_1, key, ttl));
}

它引发以下异常:

Error   5   error C2664: 'maidsafe::dht::Node::Store' : cannot convert parameter 5 from 'maidsafe::dht::PrivateKeyPtr (__cdecl *)(void)' to 'maidsafe::dht::PrivateKeyPtr'  C:\Projects\MaidSafe-DHT\src\maidsafe\dht\demo\demo_main.cc 286 1   KademliaDemo

以下几行就像一个符咒一样:

While the following lines work like a charm:

maidsafe::dht::PrivateKeyPtr pk = maidsafe::dht::PrivateKeyPtr();

kNode->node()->Store(key, value, "", ttl, pk, std::bind(&StoreCallback, args::_1, key, ttl));

推荐答案

不使用()声明它:

maidsafe::dht::PrivateKeyPtr pk;

不幸的是，对于为您提供未初始化值的原始类型，但是在C ++ 11中，您可以使用 {} 进行值初始化:

Unfortunately, for primitive types that gives you an uninitialized value, but in C++11 you can value initialize with {}:

maidsafe::dht::PrivateKeyPtr pk{};

有关相关的解析问题，请参见 c ++最令人讨厌的解析.

For a related parsing issue, see the c++ most vexing parse.

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