• Skip to main content
  • Skip to primary sidebar
  • Skip to footer
  • About
  • Life
  • Tech
  • Travel
  • Work
  • Questions
  • Contact

Welcome

.

Copy vs move in std::pair braced initialization

April 11, 2020 by

Questions › Copy vs move in std::pair braced initialization
0
Vote Up
Vote Down
Garmaine asked 4 years ago

I have the following code and its output printed below. I can't seem to understand why one set of braced initialization results in the move constructor being called, while the other results in the copy constructor. I have somewhat narrowed it down to direct-list-initialization vs copy-list-initialization per https://en.cppreference.com/w/cpp/language/list_initialization I just can't quite figure out which case my code belongs to. Thanks in advance.

#include <cstdint>
#include <iostream>
using namespace std;

struct Foo {
  Foo() {
    cout << "create foo\n";
  }

  ~Foo() {
    cout << "delete foo\n";
  }

  Foo(const Foo& f) {
    cout << "copy foo\n";
  }

  Foo(Foo&& f) noexcept {
    cout << "move foo\n";
  }

  Foo& operator=(const Foo& f) = delete;

  Foo& operator=(Foo&& f) = delete;
};

int32_t main() {
  pair<uint32_t, Foo> f1{0, Foo{}};  // Calls move ctor
  cout << "------------------------\n";

  pair<uint32_t, Foo> f2{0, {}};     // Calls copy ctor
  cout << "------------------------\n";

  return 0;
}

This results in

create foo

move foo

delete foo

------------------------

create foo

copy foo

delete foo

------------------------

delete foo

delete foo
Are you looking for the answer?
Original Question and Possible Answers can be found on `http://stackoverflow.com`

Question Tags: c++, initialization, move-semantics, std-pair, templates

Please login or Register to submit your answer




Primary Sidebar

Tags

Advancements best Business strategies commercial convenience economic Finances Cognitive decline Financial growth firm Future Hidden Gems Home hydration Impact Innovations lighting line of work Mental health Must-See New York City office patronage Productivity profession Profitability tips Profit optimization pursuit recreation Revenue enhancement romance sippy cups social station Technological breakthroughs technology toddlers trading transaction Treasures Uncover undertaking Well-being Wonders Work Young onset dementia

Newsletter

Complete the form below, and we'll send you all the latest news.

Footer

Footer Funnies

Who knew that reading the footer could be such a hilarious adventure? As we navigate websites, books, and documents, we often stumble upon the unassuming space at the bottom, only to discover a treasure trove of amusement. In this side-splitting compilation, we present 100 jokes that celebrate the unsung hero of content – the footer. Get ready to chuckle, giggle, and maybe even snort as we dive into the world of footnotes, disclaimers, and hidden comedic gems. Brace yourself for a wild ride through the footer!

Recent

  • Unveiling the Enigma: Almost-Magical Lamp Lights Highway Turns
  • The Impact of Young Onset Dementia on Employment and Finances: Optimizing Post-Diagnostic Approaches
  • 11 Wonders of 2023 Technological Breakthrough – Unveiling the Future
  • Work from Home and Stay Mentally Sane – Achieve Productivity and Well-being
  • Hidden Gems of New York City – Uncover the Must-See Treasures!

Search

Tags

Advancements best Business strategies commercial convenience economic Finances Cognitive decline Financial growth firm Future Hidden Gems Home hydration Impact Innovations lighting line of work Mental health Must-See New York City office patronage Productivity profession Profitability tips Profit optimization pursuit recreation Revenue enhancement romance sippy cups social station Technological breakthroughs technology toddlers trading transaction Treasures Uncover undertaking Well-being Wonders Work Young onset dementia

Copyright © 2023