All Questions
17 questions
1
vote
1
answer
146
views
efficient use of std::move to aggregate all object instances in a std container
I need to centrally accumulate certain entity creations in my program into a container and I want to use the efficiency of std::move with a move constructor to aggregate all entities created anwhere ...
- 530
2
votes
3
answers
4k
views
std::vector and move semantics
To enable move semantics on a std::vector do I need to pass by value; so the compiler will not copy the element but just move them?
Example:
class data
{
public:
void setMyData(vector<string>...
- 507
12
votes
1
answer
1k
views
push_back() and emplace_back() behind the scenes
I'm currently learning C++ on my own, and I am curious about how push_back() and emplace_back() work under the hood. I've always assumed that emplace_back() is faster when you are trying to construct ...
- 131
0
votes
2
answers
686
views
Difference between std::forward implementation
Recently I've been trying to understand move semantics and came up with a question.
The question has already been discussed here.
I implemented the first variant and checked whether it returns l-...
- 162
2
votes
1
answer
734
views
why std::move behaves like std::copy? [duplicate]
Consider the following piece of code -
#include <algorithm>
#include <iostream>
#include <vector>
int main()
{
std::vector<int> d {100, 200, 300};
std::vector<int&...
- 7,504
4
votes
1
answer
156
views
C++: For which objects, being "moved" implies more than "staying valid"? [duplicate]
Given that a and b are of type T, and we have either move construction (T b(move(a));) or move assignment (b = move(a)). In what cases do we know what the value of a will be?
The only one that I know ...
- 5,402
1
vote
1
answer
1k
views
std::move items out of an STL container?
I'm trying to std::move an element out of a std::set and then erase it from the set:
std::set<some_type> the_set;
some_type item;
for (auto iter = the_set.begin(); iter != the_set.end(); ...
- 4,943
7
votes
3
answers
1k
views
Why can't I std::move std::unique_ptrs between std::sets?
I really want to move some unique_ptrs from one std::set into another:
#include <memory>
#include <algorithm>
#include <set>
int main()
{
std::set<std::unique_ptr<int>&...
2
votes
2
answers
860
views
Is `unique_ptr::operator bool()` defined for a unique_ptr that has been move()d from?
It is my understanding that after I have moved from a Standard Library object, that object is in a state that is valid but undefined. But in the case of a unique_ptr, just how undefined is it? ...
- 486
5
votes
0
answers
147
views
Why do C++11 std containers have pass-by-ref and pass-by-rvalue insert/push methods? [duplicate]
I've seen many statements that when you want to copy a value inside a function it is better to pass it by value and do an std::move inside that function (since C++11). See here and here for example.
...
- 1,061
5
votes
3
answers
559
views
Why do standard library classes not overload swap() for rvalues?
STL classes define swap() method as void swap(A&), taking an l-value reference. See for example std::vector::swap, or the question Is it necessary to use std::move when swapping two objects?
Such ...
- 21.7k
0
votes
0
answers
229
views
How to use C++ std::move on object with asio io_service and acceptor member variables
I have a software to listen on ports on three NIC, so I defined TCPServer class which uses boost examples, although I am using C++11 and ASIO.
class TCPServer {
private:
asio::io_service& ...
- 1,288
2
votes
1
answer
3k
views
Is it safe to reuse a std container after std::move? [duplicate]
If I have a std::list, for example, and I use std::move() to move its information into a std::map, is it safe to reuse the list by populating it with more data so that I can add more entries to the ...
- 796
60
votes
2
answers
79k
views
Transferring the ownership of object from one unique_ptr to another unique_ptr in C++11?
In C++11 we can transfer the ownership of an object to another unique_ptr using std::move(). After the ownership transfer, the smart pointer that ceded the ownership becomes null and get() returns ...
- 1,796
7
votes
1
answer
729
views
Returning std::move(f) in std::for_each
I'm writing an implementation of standard c++ library for study.
The C++11 standard says that for_each returns std::move(f).
template <class InputIterator, class Function>
Function for_each(...
- 4,103
4
votes
1
answer
2k
views
What can I use instead of std::move()?
I'm using a C++ compiler with the C++0x specification, and want to make my move constructor for a String class that wraps around a std::wstring.
class String {
public:
String(String&& str)...
- 3,191
33
votes
4
answers
15k
views
Is this correct usage of C++ 'move' semantics? [duplicate]
Tonight I've been taking a look at some code I've been working on over the last few days, and began reading up on move semantics, specifically std::move. I have a few questions to ask you pros to ...
- 38.8k