Initializes an object from another object
Questions tagged [copy-initialization]
52 questions
2
votes
1 answer
C++ object construction -- direct initialization versus using the '=' operator, are they equivalent?
In C++, are these two styles of initializing a class-object functionally equivalent, or are there some situations where they might have differing semantics and generate different code?
SomeClass foo(1,2,3);
vs
auto foo = SomeClass(1,2,3);
Jeremy Friesner
- 70,199
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2
votes
1 answer
Why does the class reference constructor overload get called from an rvalue when there's an rvalue constructor available?
This code
#include
struct A
{
A(int i) {std::cout << "int received\n";}
A(A& a) {std::cout << "ref received\n";}
};
int main()
{
int j = 5;
A a = j;
}
unexpectedly throws the following compiler error:
error: invalid…
GT 77
- 448
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- 12
2
votes
1 answer
Difference copy-initialization and direct-initialization for primitive (scalar) types
as far as I understand in C++ is an initialization in the form
T x = a;
called copy-initialization and an initialization in the form
T x(a);
or
T x{a};
called direct-initialization.
(T...Type, x...variable name, a...expression)
For class types…
knowledge
- 941
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- 26
2
votes
2 answers
no matching function in template class
I get no matching member function error when i try to compile this code on my mingw32 compiler
#include
using std::cout;
template
class Pattern
{
public:
Pattern(): element(){
cout<< "default c-tor";
}
…
Brian
- 21
- 1
2
votes
1 answer
Do implicit class-type conversions use the copy-constructor?
The following quote from my C++ book:
When we use direct initialization, we are asking the compiler to use ordinary function matching to select the constructor that best matches the arguments
we provide. When we use copy initialization, we are…
Silversonic
- 1,289
- 2
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2
votes
2 answers
Explicit and non-explicit constructors
class Test
{
public:
Test(int i) { cout<<"constructor called\n";}
Test(const Test& t) { cout<<" copy constructor called\n";}
};
class Test1
{
public:
Test1(int i) { cout<<"constructor…
Achyuta Aich
- 85
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- 9
1
vote
1 answer
Why this copy-initialization (with two implicit conversions) does not work in GCC/Clang?
Please consider the following code:
#include
class cstring {
public:
cstring(const char* str) : begin_(str), end_(str ? str + strlen(str) : 0)
{
}
size_t size() const
{
return (size_t)(end_ - begin_);
}
…
amanjiang
- 1,213
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- 33
1
vote
1 answer
C++ Stringstream initializations
I have two code snippets:
This does not compile:
std::string reverseSentence(std::string sentence) {
std::stringstream stream = sentence;
}
This does:
std::stringstream stream (sentence);
It's my understanding that T foo = expr is T…
nz_21
- 6,140
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1
vote
2 answers
Difference between = and {} syntaxes for initializing a variable in C++
I have read quite a few C++ codes, and I have come across two methods of initialising a variable.
Method 1:
int score = 0;
Method 2:
int score {};
I know that int score {}; will initialise the score to 0, and so will int score = 0;
What is the…
Aditya Prakash
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1
vote
1 answer
To Clarify my insights to copy initialization and direct initialization
Define a class as follows:
class A {
public:
A(): s("") {} //default constructor
A(const char* pStr): s(pStr) {} //constructor with parameter
A(const A& a) : s(a.s) {} //copy constructor
…
Finley
- 795
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1
vote
0 answers
Why do we differ between copy and direct initialization?
I have following questions and I hope you can help me.
Code:
A a; //A(void) is called
A b(a); //A(const A&) is called: direct-initialization
A c = a; //A(const A&) is called: copy-initialization
Why are we differ between these initializations?
1)…
zuuurek
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1
vote
2 answers
C++ copy initialization + implicit constructor call = fail
This code:
class foo
{
int x;
public:
foo(int x) : x(x) { }
int get() const { return x; }
//...
};
class bar
{
int x;
public:
bar(const foo& x) : x(x.get()) { }
int get() const { return x; }
bar& operator =(const…
fincs
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0
votes
1 answer
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 parenthesized list of expressions
It is direct…
Kevin eyeson
- 375
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0
votes
1 answer
Why copy intialisation is used instead of direct initialisation when passing argument to function parameter by value
I am learning C++ using the resources listed here. In particular, I came to know that copy initialization is used when passing arguments to function parameters(by value) etc.
For example, from decl.init.general#14:
The initialization that occurs in…
Kal
- 475
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- 16
0
votes
2 answers
Ambiguous Class Template Conversion
How would one add a template constructor to the class so that copy initialization from complex to complex is performed explicitly and without ambiguity? Is there a solution that is compiler and C++ version/standard agnostic? Is there an approach…
Darnoc Eloc
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