Questions tagged [direct-initialization]
Initializes an object from explicit set of constructor arguments.
direct-initialization
19
questions
5
votes
1
answer
154
views
Why does direct initialization use a const lvalue reference qualified conversion function?
I have two classes st and foo:
struct st {
st() = default;
st(const st&) {
std::cout << "copy ctor." << std::endl;
}
st(st&&) {
std::...
- 283
2
votes
1
answer
72
views
Why does direct-initialization not work for std::views::iota?
Why is this an illegal declaration?
> std::views::iota r(0, 10);
error: expected ‘;’ before ‘r’
but this works
> auto r = std::views::iota(0, 10);
- 85
3
votes
1
answer
51
views
Why does direct initializing a base class member from a prvalue require a copy or move constructor?
It is well known that for a class with deleted copy and move constructors, it is still possible to direct initialize an object from a prvalue such as the return value of a function. For example, this ...
- 33
1
vote
1
answer
90
views
Why warning instead of hard error on ill formed program [duplicate]
I'm aware that uniform initialization using braced-init list don't allow narrow conversion (ex double -> int)
but member initialization using init list allows narrow conversion.
struct Mem1
{
...
- 69
20
votes
1
answer
863
views
Why does this code generate different output for different compilers?
I have the following code:
#include <iostream>
#include <vector>
struct C {
int a;
C() : a(0) {}
C(int a) : a(a) {}
};
std::ostream &operator<<(std::ostream &os, ...
- 217
0
votes
0
answers
61
views
Variable declaration by calling its constructor [duplicate]
In some Boost ASIO example, I found the line auto self(shared_from_this());. self doesn't seem to be declared anywhere and doesn't seem to be a reserved keyword. In another example, I also found the ...
- 16.5k
0
votes
1
answer
61
views
In C++, under the case `T object(other);`, is it direct initialization or copy initialization？
Assume I have this code
T object(other);
It is direct initialization or copy initialization? Based on the rule of direct initialization :
T object ( arg ); initialization with a nonempty ...
- 363
2
votes
1
answer
104
views
Direct initialization != copy initialization when converting from different type? [duplicate]
I always thought direct initialization and copy initialization for types T that do not match the class type are absolutely equal. Yet I seem to be mistaken. The following code doesn't compile if I ...
- 4,475
0
votes
1
answer
372
views
How to list-initialize an initializer_list from another initializer_list
When I'm trying to compile the following code, the compiler complains:
int main(void)
{
std::initializer_list<int> lst1{};
std::initializer_list<int> lst2{lst1}; // error
}
The ...
- 1,932
5
votes
2
answers
109
views
Direct initialization with prvalue: Bug in MSVC?
Consider the following code:
struct S
{
S(int, double) {}
explicit S(const S&) {}
explicit S(S&&) {}
};
void i_take_an_S(S s) {}
S i_return_an_S() { return S{ 4, 2.0 }; }
...
- 509
1
vote
2
answers
140
views
In which case(s) user-defined conversions are not considered during reference initialization?
Consider a case where we've reached into bullet [dcl.init.ref]/(5.4.1) during reference binding:
(5.4.1) If T1 or T2 is a class type and T1 is not reference-related to
T2, user-defined conversions ...
- 1,932
4
votes
1
answer
208
views
Copy-elision in direct initialization from braced-init-list
In the following program the object A a is directly initialized from braced-init-list {A{}}:
#include <iostream>
struct A {
int v = 0;
A() {}
A(const A &) : v(1) {}
};
int main(...
- 19.3k
2
votes
1
answer
291
views
Is direct-initialization equivalent to direct-list-initialization?
I have the following example:
struct S{
int x, y;
}
S s1{1}; // direct-initialization or direct-list-initialization ?
S s2{1, 2}; // direct-initialization or direct-list-initialization ?
S s3(1)...
- 1,932
4
votes
1
answer
1k
views
Initialization in return statements of functions that return by-value
My question originates from delving into std::move in return statements, such as in the following example:
struct A
{
A() { std::cout << "Constructed " << this << std::...
- 509
1
vote
1
answer
58
views
Initialization in C++
What is the difference between direct initialization and uniform initialization in C++?
What is the difference between writing
int a{5}; // Uniform
and
int a(5); // Direct
- 35