incomplete-type Questions
4
Solved
The code snippet below demonstrates a real issue I faced recently in my program:
#include<vector>
class A;
void f( const std::vector<A> & = {} );
There is an incomplete class A, ...
Fanciful asked 30/10, 2023 at 20:16
3
Solved
I would like to write a C++ function that will check that its template parameter class is incomplete, so only class declaration is available but not full definition with all class members.
My...
Jehad asked 29/7, 2021 at 9:50
4
Solved
This code is giving me incomplete type error.
What is the problem? Isn't allowed for a class to have static member instances of itself?
Is there a way to achieve the same result?
struct Size
{
co...
Cheremkhovo asked 3/3, 2016 at 18:32
4
Solved
Is it legal to use an incomplete type in a template if the type is complete when the template is instantiated?
As below
#include <iostream>
struct bar;
template <typename T>
struct fo...
Valorie asked 25/10, 2021 at 17:38
2
Solved
For example:
class B;
class A {
public:
B f();
};
int main(int, char**) {
A a; // no exception and error
return 0;
}
The class A may be an incomplete type.
Why can class A be instantiated in...
Tuneberg asked 12/2, 2023 at 9:30
1
Solved
The code below compiles OK (see Golbolt link below):
#include <memory>
struct B;
struct A1 {
A1() = default;
~A1();
std::unique_ptr<B> ptr;
};
#if 0
struct A2 {
A2();
~A2();
st...
Barbados asked 10/2, 2023 at 9:32
2
Solved
From Is std::unique_ptr required to know the full definition of T?, I know that if a class A has a member unique_ptr<T>, then T shall be a complete type in destructor ~A(). However, I came ac...
Meredithmeredithe asked 10/2, 2023 at 8:36
4
Solved
Consider this example:
#include <iostream>
#include <type_traits>
template <class, class = void>
struct is_defined : std::false_type
{ };
template <class T>
struct is_def...
Ingrained asked 2/10, 2016 at 12:0
1
Solved
According to Template parameters and template arguments on cppreference.com:
A template argument for a type template parameter must be a type-id,
which may name an incomplete type
That means that...
Comedian asked 2/4, 2022 at 12:27
7
Solved
The below line gives me error :
Incompatible Types.
List<List<Integer>> output = new ArrayList<ArrayList<Integer>>();
What is the reason?
EDIT
I understand if I chang...
Gaia asked 17/7, 2014 at 6:26
2
Is an lvalue required to have a complete type? If no, then is *x where x has an incomplete type valid?
Note: for "modifiable lvalue" there is (emphasis added):
A modifiable lvalue ...
Moonrise asked 15/2, 2022 at 16:3
3
Solved
The following code compiles fine.
header.h:
typedef struct Placeholder_Type* Placeholder;
impl.cpp:
#include "header.h"
void doSomething(Placeholder t) {
(void) t;
}
int main() {
in...
Retaliate asked 3/2, 2022 at 7:50
2
Solved
In the following example function f() returning incomplete type A is marked as deleted:
struct A;
A f() = delete;
It is accepted by GCC, but not in Clang, which complains:
error: incomplete result...
Tammietammuz asked 19/12, 2021 at 10:20
2
To my knowledge I'm initializing a string a fairly normal way and when I debug, the variables window in my IDE (CLion) shows its value as <incomplete type>. I have some simple code that resul...
Sound asked 17/10, 2017 at 4:13
1
Solved
Please consider a struct A having a field u of type U<R> with a default initializer. The destructor ~U<R> is only declared:
template<typename T>
struct U {
~U();
};
struct R;
s...
Capers asked 21/8, 2021 at 6:28
1
Solved
In the following code:
#include <memory>
struct A;
std::unique_ptr<A> ok() { return {}; }
std::unique_ptr<A> error() { return std::unique_ptr<A>{}; }
Clang++ compiles f...
Keratosis asked 6/8, 2021 at 8:59
2
Solved
What I mean, is it possible to somehow do something like this?
class Color {
public:
static constexpr Color BLACK = {0, 0, 0};
constexpr Color(int r, int g, int b) : r_(r), g_(g), b_(b) {}
priv...
Cochard asked 9/7, 2021 at 10:35
3
Solved
I have declared a struct, and I try to pass an array of those structs (as well as a double array of doubles, and an integer) into a function. I get an "array type has incomplete element type&q...
Shelby asked 4/4, 2012 at 0:15
1
Solved
Given an incomplete type:
struct S;
Then the following declarations are:
S *p; // ok, pointer to incomplete types is allowed
std::deque<S> l; // error, instantiating std::deque with incomp...
Cayes asked 23/7, 2020 at 18:49
3
Solved
Sometimes it's useful to instantiate a standard container with an incomplete type to obtain a recursive structure:
struct multi_tree_node { // Does work in most implementations
std::vector< mu...
Hydrokinetics asked 30/11, 2011 at 16:57
1
Solved
This is a language-lawyer follow up to this question, where all the answers agree that the following is not allowed:
struct A { A a; };
There are several instances where incomplete types can be ...
Isomer asked 22/4, 2020 at 3:22
1
Solved
Can int (*)[] be an incomplete type?
C 2018 6.2.5 1 says:
At various points within a translation unit an object type may be incomplete (lacking sufficient information to determine the size of o...
Prunelle asked 13/1, 2020 at 21:53
2
Solved
Consider this example (coming from here):
#include <type_traits>
#include <iostream>
template <typename U>
struct A {
};
struct B {
template <typename F = int>
A&l...
Tressietressure asked 10/12, 2019 at 13:12
1
Solved
Given the following class template:
template<typename T>
struct Outer
{
struct Inner;
auto f(Inner) -> void;
};
we define Inner separately for each specialization of Outer:
template...
Tompkins asked 19/11, 2019 at 14:45
1
The following code compiles and links with Visual Studio (both 2017 and 2019 with /permissive-), but does not compile with either gcc or clang.
foo.h
#include <memory>
struct Base {
vir...
Spermatozoid asked 22/10, 2019 at 14:36
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