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Why Would Different Pointers Act As If They Shared The Same Values?


Why Would Different Pointers Act As If They Shared The Same Values?

By : Eugene Orlovsky
Date : November 22 2020, 10:48 AM
This might help you MakePtrArrayB invokes undefined behavior, by using an uninitialized pointer.
Undefined behavior can be anything, but in your case, the myArr pointer in MakePtrArrayB probably occupies the same memory as the one in MakePtrArrayA, so the loop accesses the original array (setting it to newly allocated row buffers that are big enough for the subsequent accesses).
code :


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Pointers, smart pointers or shared pointers?

Pointers, smart pointers or shared pointers?


By : Imp4ct
Date : March 29 2020, 07:55 AM
wish helps you Sydius outlined the types fairly well:
Normal pointers are just that - they point to some thing in memory somewhere. Who owns it? Only the comments will let you know. Who frees it? Hopefully the owner at some point. Smart pointers are a blanket term that cover many types; I'll assume you meant scoped pointer which uses the RAII pattern. It is a stack-allocated object that wraps a pointer; when it goes out of scope, it calls delete on the pointer it wraps. It "owns" the contained pointer in that it is in charge of deleteing it at some point. They allow you to get a raw reference to the pointer they wrap for passing to other methods, as well as releasing the pointer, allowing someone else to own it. Copying them does not make sense. Shared pointers is a stack-allocated object that wraps a pointer so that you don't have to know who owns it. When the last shared pointer for an object in memory is destructed, the wrapped pointer will also be deleted.
Boost shared pointers C++ : shared pointer unable to free resource on release

Boost shared pointers C++ : shared pointer unable to free resource on release


By : user3645582
Date : March 29 2020, 07:55 AM
Does that help Why is the manager holding a shared_ptr (strong reference) to the object if it doesn't need to retain control, only pass it on? Not seeing your code, it seems like having the manager hold a weak_ptr and then pass that on to the workers, who lock it into a shared_ptr on their end. That will allow the manager to pass on references without owning one of its own.
code :
class Worker
{
    SomeSharedPointer my_sp;

    Worker()
    {
        String someUniqueId = "http://blah.com"
        weak_ptr wp = Manager::getResource(someUniqueId);
        my_sp = wp.lock();

        // do some work on the resource
    }

    ~Worker()
    {
        //my_sp.reset(); // handled automatically, as part of how shared pointers work
    }
}
What is the difference between auto pointers and shared pointers in C++

What is the difference between auto pointers and shared pointers in C++


By : user3851539
Date : March 29 2020, 07:55 AM
Hope that helps std::auto_ptr is an outdated, deprecated implementation of exclusive pointer ownership. It's been replaced by std::unique_ptr in C++11. Exclusive ownership means that the pointer is owned by something, and the lifetime of the object is tied to the lifetime of the owner.
Shared pointers (std::shared_ptr) implement shared pointer ownership — they keep the object alive as long as there are alive references to it, because there is no single owner. It's usually done with reference counting, which means they have additional runtime overhead as opposed to unique pointers. Also reasoning about shared ownership is more difficult than reasoning about exclusive ownership — the point of destruction becomes less deterministic.
copy object behind shared pointer containing a list of shared pointers

copy object behind shared pointer containing a list of shared pointers


By : Faisal ahsan
Date : March 29 2020, 07:55 AM
around this issue The entire subtree has to be cloned, not just the sub-root. Since none of the pointers are copied, it is not useful to copy initialize the clone. Also, you should avoid bare pointers to allocated memory in order to guarantee strong exception safety.
Untested example:
code :
std::shared_ptr<TreeNode> TreeNode::clone() const
{
    auto clone = std::make_shared<TreeNode>();
    clone->children->reserve(children->size());
    for(const auto& c : *children) {
        auto c_clone = c->clone();
        c_clone->setParent(clone);
        clone->children->push_back(c_clone);
    }
    return clone;
}
Any reason behind the syntax difference between shared pointers and unique pointers with custom deleters

Any reason behind the syntax difference between shared pointers and unique pointers with custom deleters


By : Jan Wissing
Date : March 29 2020, 07:55 AM
Any of those help The default std::unique_ptr is only storing one element, the pointer to the data it protects. This is because by default, you want to use the least amount of memory possible. But when you specify a deleter, you need also to store it. So you need to differentiate between the two versions.
See here: https://github.com/llvm-mirror/libcxx/blob/master/include/memory#L2397
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