Question

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));
}

It throws the following exception:

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

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));

Answer 1

Declare it without the ():

maidsafe::dht::PrivateKeyPtr pk;

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

maidsafe::dht::PrivateKeyPtr pk{};

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