Mixing
Storing a unique_ptr with custom deleter in a map
Clash Royale CLAN TAG#URR8PPP
up vote
7
down vote
favorite
Why doesn't this work?
#include <map>
#include <memory>
void deleter(int* i)
delete i;
std::map<int, std::unique_ptr<int, decltype(&deleter)>> m;
void foo(int* i)
m[0] = std::unique_ptr<int, decltype(&deleter)>(i, &deleter);
Check out the incomprehensible compile error https://godbolt.org/z/Uhp9NO.
c++ unique-ptr
edited 50 mins ago
François Andrieux
14.3k32244
asked 53 mins ago
Timmmm
34.6k26183240
add a comment |Â
up vote
7
down vote
favorite
Why doesn't this work?
#include <map>
#include <memory>
void deleter(int* i)
delete i;
std::map<int, std::unique_ptr<int, decltype(&deleter)>> m;
void foo(int* i)
m[0] = std::unique_ptr<int, decltype(&deleter)>(i, &deleter);
Check out the incomprehensible compile error https://godbolt.org/z/Uhp9NO.
c++ unique-ptr
edited 50 mins ago
François Andrieux
14.3k32244
asked 53 mins ago
Timmmm
34.6k26183240
4
I don't know why this is getting downvotes, it's a good question. Perhaps it's the link. People might see it as a link to external code. To be clear to other readers, it's a live sample at godbolt. Edit : I've edited the question to make the nature of the link more obvious.
– François Andrieux
50 mins ago
2
You need to post errors here.
– Maxim Egorushkin
49 mins ago
They are very long, and only a click away. That seem excessive.
– Timmmm
49 mins ago
This is relevant: stackoverflow.com/questions/17906325/…
– zoska
49 mins ago
On a mobile it is extremely difficult to view errors from godbolt
– Robert Andrzejuk
32 mins ago
add a comment |Â
up vote
7
down vote
favorite
up vote
7
down vote
favorite
Why doesn't this work?
#include <map>
#include <memory>
void deleter(int* i)
delete i;
std::map<int, std::unique_ptr<int, decltype(&deleter)>> m;
void foo(int* i)
m[0] = std::unique_ptr<int, decltype(&deleter)>(i, &deleter);
Check out the incomprehensible compile error https://godbolt.org/z/Uhp9NO.
c++ unique-ptr
edited 50 mins ago
François Andrieux
14.3k32244
asked 53 mins ago
Timmmm
34.6k26183240
Why doesn't this work?
#include <map>
#include <memory>
void deleter(int* i)
delete i;
std::map<int, std::unique_ptr<int, decltype(&deleter)>> m;
void foo(int* i)
m[0] = std::unique_ptr<int, decltype(&deleter)>(i, &deleter);
Check out the incomprehensible compile error https://godbolt.org/z/Uhp9NO.
c++ unique-ptr
c++ unique-ptr
edited 50 mins ago
François Andrieux
14.3k32244
asked 53 mins ago
Timmmm
34.6k26183240
edited 50 mins ago
François Andrieux
14.3k32244
asked 53 mins ago
Timmmm
34.6k26183240
edited 50 mins ago
François Andrieux
14.3k32244
edited 50 mins ago
François Andrieux
14.3k32244
edited 50 mins ago
François Andrieux
14.3k32244
14.3k32244
asked 53 mins ago
Timmmm
34.6k26183240
asked 53 mins ago
Timmmm
34.6k26183240
asked 53 mins ago
Timmmm
34.6k26183240
34.6k26183240
4
I don't know why this is getting downvotes, it's a good question. Perhaps it's the link. People might see it as a link to external code. To be clear to other readers, it's a live sample at godbolt. Edit : I've edited the question to make the nature of the link more obvious.
– François Andrieux
50 mins ago
2
You need to post errors here.
– Maxim Egorushkin
49 mins ago
They are very long, and only a click away. That seem excessive.
– Timmmm
49 mins ago
This is relevant: stackoverflow.com/questions/17906325/…
– zoska
49 mins ago
On a mobile it is extremely difficult to view errors from godbolt
– Robert Andrzejuk
32 mins ago
add a comment |Â
4
I don't know why this is getting downvotes, it's a good question. Perhaps it's the link. People might see it as a link to external code. To be clear to other readers, it's a live sample at godbolt. Edit : I've edited the question to make the nature of the link more obvious.
– François Andrieux
50 mins ago
2
You need to post errors here.
– Maxim Egorushkin
49 mins ago
They are very long, and only a click away. That seem excessive.
– Timmmm
49 mins ago
This is relevant: stackoverflow.com/questions/17906325/…
– zoska
49 mins ago
On a mobile it is extremely difficult to view errors from godbolt
– Robert Andrzejuk
32 mins ago
4
4
I don't know why this is getting downvotes, it's a good question. Perhaps it's the link. People might see it as a link to external code. To be clear to other readers, it's a live sample at godbolt. Edit : I've edited the question to make the nature of the link more obvious.
– François Andrieux
50 mins ago
I don't know why this is getting downvotes, it's a good question. Perhaps it's the link. People might see it as a link to external code. To be clear to other readers, it's a live sample at godbolt. Edit : I've edited the question to make the nature of the link more obvious.
– François Andrieux
50 mins ago
2
2
You need to post errors here.
– Maxim Egorushkin
49 mins ago
You need to post errors here.
– Maxim Egorushkin
49 mins ago
They are very long, and only a click away. That seem excessive.
– Timmmm
49 mins ago
They are very long, and only a click away. That seem excessive.
– Timmmm
49 mins ago
This is relevant: stackoverflow.com/questions/17906325/…
– zoska
49 mins ago
This is relevant: stackoverflow.com/questions/17906325/…
– zoska
49 mins ago
On a mobile it is extremely difficult to view errors from godbolt
– Robert Andrzejuk
32 mins ago
On a mobile it is extremely difficult to view errors from godbolt
– Robert Andrzejuk
32 mins ago
add a comment |Â
2 Answers
2
active
oldest
votes
up vote
14
down vote
accepted
The problem is that m[0] calls the default constructor of std::unique_ptr<int, decltype(&deleter)>, which is not available because it requires the deleter pointer.
Fix:
struct Deleter
void operator()(int* i) delete i;
;
std::map<int, std::unique_ptr<int, Deleter>> m;
void foo(int* i)
m[0] = std::unique_ptr<int, Deleter>(i);
This is also more efficient than std::unique_ptr<int, decltype(&deleter)> because it does not have to store the very same pointer to deleter in each instance of std::unique_ptr. I.e. sizeof(std::unique_ptr<int, Deleter>) < sizeof(std::unique_ptr<int, decltype(&deleter)>).
answered 49 mins ago
Maxim Egorushkin
81.3k1195178
add a comment |Â
up vote
7
down vote
std::unique_ptr, when using a custom deleter function like you have, is not default constructable. std::map::operator requires that the value type of the map be default constructable. That means as is you cannot use operator with this type of map.
In order for std::unique_ptr to be default constructable you need a deleter that satisfies where std::is_default_constructible<Deleter>::value is true and Deleter is not a pointer type.
answered 49 mins ago
NathanOliver
77.5k15104158
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
14
down vote
accepted
The problem is that m[0] calls the default constructor of std::unique_ptr<int, decltype(&deleter)>, which is not available because it requires the deleter pointer.
Fix:
struct Deleter
void operator()(int* i) delete i;
;
std::map<int, std::unique_ptr<int, Deleter>> m;
void foo(int* i)
m[0] = std::unique_ptr<int, Deleter>(i);
This is also more efficient than std::unique_ptr<int, decltype(&deleter)> because it does not have to store the very same pointer to deleter in each instance of std::unique_ptr. I.e. sizeof(std::unique_ptr<int, Deleter>) < sizeof(std::unique_ptr<int, decltype(&deleter)>).
answered 49 mins ago
Maxim Egorushkin
81.3k1195178
add a comment |Â
up vote
14
down vote
accepted
The problem is that m[0] calls the default constructor of std::unique_ptr<int, decltype(&deleter)>, which is not available because it requires the deleter pointer.
Fix:
struct Deleter
void operator()(int* i) delete i;
;
std::map<int, std::unique_ptr<int, Deleter>> m;
void foo(int* i)
m[0] = std::unique_ptr<int, Deleter>(i);
This is also more efficient than std::unique_ptr<int, decltype(&deleter)> because it does not have to store the very same pointer to deleter in each instance of std::unique_ptr. I.e. sizeof(std::unique_ptr<int, Deleter>) < sizeof(std::unique_ptr<int, decltype(&deleter)>).
answered 49 mins ago
Maxim Egorushkin
81.3k1195178
add a comment |Â
up vote
14
down vote
accepted
up vote
14
down vote
accepted
The problem is that m[0] calls the default constructor of std::unique_ptr<int, decltype(&deleter)>, which is not available because it requires the deleter pointer.
Fix:
struct Deleter
void operator()(int* i) delete i;
;
std::map<int, std::unique_ptr<int, Deleter>> m;
void foo(int* i)
m[0] = std::unique_ptr<int, Deleter>(i);
This is also more efficient than std::unique_ptr<int, decltype(&deleter)> because it does not have to store the very same pointer to deleter in each instance of std::unique_ptr. I.e. sizeof(std::unique_ptr<int, Deleter>) < sizeof(std::unique_ptr<int, decltype(&deleter)>).
answered 49 mins ago
Maxim Egorushkin
81.3k1195178
The problem is that m[0] calls the default constructor of std::unique_ptr<int, decltype(&deleter)>, which is not available because it requires the deleter pointer.
Fix:
struct Deleter
void operator()(int* i) delete i;
;
std::map<int, std::unique_ptr<int, Deleter>> m;
void foo(int* i)
m[0] = std::unique_ptr<int, Deleter>(i);
This is also more efficient than std::unique_ptr<int, decltype(&deleter)> because it does not have to store the very same pointer to deleter in each instance of std::unique_ptr. I.e. sizeof(std::unique_ptr<int, Deleter>) < sizeof(std::unique_ptr<int, decltype(&deleter)>).
answered 49 mins ago
Maxim Egorushkin
81.3k1195178
answered 49 mins ago
Maxim Egorushkin
81.3k1195178
answered 49 mins ago
Maxim Egorushkin
81.3k1195178
answered 49 mins ago
Maxim Egorushkin
81.3k1195178
81.3k1195178
add a comment |Â
add a comment |Â
up vote
7
down vote
std::unique_ptr, when using a custom deleter function like you have, is not default constructable. std::map::operator requires that the value type of the map be default constructable. That means as is you cannot use operator with this type of map.
In order for std::unique_ptr to be default constructable you need a deleter that satisfies where std::is_default_constructible<Deleter>::value is true and Deleter is not a pointer type.
answered 49 mins ago
NathanOliver
77.5k15104158
add a comment |Â
up vote
7
down vote
std::unique_ptr, when using a custom deleter function like you have, is not default constructable. std::map::operator requires that the value type of the map be default constructable. That means as is you cannot use operator with this type of map.
In order for std::unique_ptr to be default constructable you need a deleter that satisfies where std::is_default_constructible<Deleter>::value is true and Deleter is not a pointer type.
answered 49 mins ago
NathanOliver
77.5k15104158
add a comment |Â
up vote
7
down vote
up vote
7
down vote
std::unique_ptr, when using a custom deleter function like you have, is not default constructable. std::map::operator requires that the value type of the map be default constructable. That means as is you cannot use operator with this type of map.
In order for std::unique_ptr to be default constructable you need a deleter that satisfies where std::is_default_constructible<Deleter>::value is true and Deleter is not a pointer type.
answered 49 mins ago
NathanOliver
77.5k15104158
std::unique_ptr, when using a custom deleter function like you have, is not default constructable. std::map::operator requires that the value type of the map be default constructable. That means as is you cannot use operator with this type of map.
In order for std::unique_ptr to be default constructable you need a deleter that satisfies where std::is_default_constructible<Deleter>::value is true and Deleter is not a pointer type.
answered 49 mins ago
NathanOliver
77.5k15104158
edited 43 mins ago
answered 49 mins ago
NathanOliver
77.5k15104158
answered 49 mins ago
NathanOliver
77.5k15104158
answered 49 mins ago
NathanOliver
77.5k15104158
77.5k15104158
add a comment |Â
add a comment |Â
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4
I don't know why this is getting downvotes, it's a good question. Perhaps it's the link. People might see it as a link to external code. To be clear to other readers, it's a live sample at godbolt. Edit : I've edited the question to make the nature of the link more obvious.
– François Andrieux
50 mins ago
2
You need to post errors here.
– Maxim Egorushkin
49 mins ago
They are very long, and only a click away. That seem excessive.
– Timmmm
49 mins ago
This is relevant: stackoverflow.com/questions/17906325/…
– zoska
49 mins ago
On a mobile it is extremely difficult to view errors from godbolt
– Robert Andrzejuk
32 mins ago