Mixing
Using single-member structs as the member itself
I use structs to expose a typesafish interface, like:
class IFoo
{
virtual HRESULT bar(struct _BAR * arg) = 0;
}
Behind the scene, each implementation of this interface defines its own struct:
struct _BAR { Baz baz };
I currently call many allocation functions this way:
HRESULT allocate(Baz ** baz);
_BAR * bar;
ret = allocate( (Baz **) &bar );
Is it possible to call them with a more type-safe cast, like static_cast, by adding data in the struct _BAR definition?
c++ visual-c++
asked Dec 19 '18 at 13:51
bartavellebartavelle
772614
add a comment |
I use structs to expose a typesafish interface, like:
class IFoo
{
virtual HRESULT bar(struct _BAR * arg) = 0;
}
Behind the scene, each implementation of this interface defines its own struct:
struct _BAR { Baz baz };
I currently call many allocation functions this way:
HRESULT allocate(Baz ** baz);
_BAR * bar;
ret = allocate( (Baz **) &bar );
Is it possible to call them with a more type-safe cast, like static_cast, by adding data in the struct _BAR definition?
c++ visual-c++
asked Dec 19 '18 at 13:51
bartavellebartavelle
772614
2
Heads-up: you have UB here through the pointer cast, but also from the conflicting definitions of_BARwhich violate ODR. I think you're knee-deep in a solution which won't pan out.
– Quentin
Dec 19 '18 at 14:05
1
each implementation defines its own struct?_BARhas to be always the same type, and you cannot define the same type more than once
– user463035818
Dec 19 '18 at 14:05
Alright, I went with a distinct solution. Is this question useful or should I just delete it?
– bartavelle
Dec 19 '18 at 15:19
add a comment |
I use structs to expose a typesafish interface, like:
class IFoo
{
virtual HRESULT bar(struct _BAR * arg) = 0;
}
Behind the scene, each implementation of this interface defines its own struct:
struct _BAR { Baz baz };
I currently call many allocation functions this way:
HRESULT allocate(Baz ** baz);
_BAR * bar;
ret = allocate( (Baz **) &bar );
Is it possible to call them with a more type-safe cast, like static_cast, by adding data in the struct _BAR definition?
c++ visual-c++
asked Dec 19 '18 at 13:51
bartavellebartavelle
772614
I use structs to expose a typesafish interface, like:
class IFoo
{
virtual HRESULT bar(struct _BAR * arg) = 0;
}
Behind the scene, each implementation of this interface defines its own struct:
struct _BAR { Baz baz };
I currently call many allocation functions this way:
HRESULT allocate(Baz ** baz);
_BAR * bar;
ret = allocate( (Baz **) &bar );
Is it possible to call them with a more type-safe cast, like static_cast, by adding data in the struct _BAR definition?
c++ visual-c++
c++ visual-c++
asked Dec 19 '18 at 13:51
bartavellebartavelle
772614
asked Dec 19 '18 at 13:51
bartavellebartavelle
772614
asked Dec 19 '18 at 13:51
bartavellebartavelle
772614
asked Dec 19 '18 at 13:51
bartavellebartavelle
772614
asked Dec 19 '18 at 13:51
bartavellebartavelle
772614
772614
2
Heads-up: you have UB here through the pointer cast, but also from the conflicting definitions of_BARwhich violate ODR. I think you're knee-deep in a solution which won't pan out.
– Quentin
Dec 19 '18 at 14:05
1
each implementation defines its own struct?_BARhas to be always the same type, and you cannot define the same type more than once
– user463035818
Dec 19 '18 at 14:05
Alright, I went with a distinct solution. Is this question useful or should I just delete it?
– bartavelle
Dec 19 '18 at 15:19
add a comment |
2
Heads-up: you have UB here through the pointer cast, but also from the conflicting definitions of_BARwhich violate ODR. I think you're knee-deep in a solution which won't pan out.
– Quentin
Dec 19 '18 at 14:05
1
each implementation defines its own struct?_BARhas to be always the same type, and you cannot define the same type more than once
– user463035818
Dec 19 '18 at 14:05
Alright, I went with a distinct solution. Is this question useful or should I just delete it?
– bartavelle
Dec 19 '18 at 15:19
2
2
Heads-up: you have UB here through the pointer cast, but also from the conflicting definitions of
_BAR which violate ODR. I think you're knee-deep in a solution which won't pan out.– Quentin
Dec 19 '18 at 14:05
Heads-up: you have UB here through the pointer cast, but also from the conflicting definitions of
_BAR which violate ODR. I think you're knee-deep in a solution which won't pan out.– Quentin
Dec 19 '18 at 14:05
1
1
each implementation defines its own struct?
_BAR has to be always the same type, and you cannot define the same type more than once– user463035818
Dec 19 '18 at 14:05
each implementation defines its own struct?
_BAR has to be always the same type, and you cannot define the same type more than once– user463035818
Dec 19 '18 at 14:05
Alright, I went with a distinct solution. Is this question useful or should I just delete it?
– bartavelle
Dec 19 '18 at 15:19
Alright, I went with a distinct solution. Is this question useful or should I just delete it?
– bartavelle
Dec 19 '18 at 15:19
add a comment |
2 Answers
2
active
oldest
votes
As mentioned in the comments by @Quentin, this is a violation of ODR (one definition rule). I am not sure what your purpose is, but you can consider 2 things to meet your need. One is using a template. The other one is to use void *. but I am just guessing and hope that helps.
answered Dec 19 '18 at 14:11
CS PeiCS Pei
8,4182040
Ah I see. I can perhaps use templates, although I am not sure how to solve this. I could make the structures public, and have them have a singlevoid *member to ensure "type safetyness" on the caller side.
– bartavelle
Dec 19 '18 at 14:46
add a comment |
I would make an empty structure as a base:
// For base interface
struct _BAR {};
// For an implementation
struct Baz : BAR { ... };
In this case static_cast would do, and it will be legal C++
answered Jan 1 at 8:55
Alexander GutenevAlexander Gutenev
1,072918
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
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votes
As mentioned in the comments by @Quentin, this is a violation of ODR (one definition rule). I am not sure what your purpose is, but you can consider 2 things to meet your need. One is using a template. The other one is to use void *. but I am just guessing and hope that helps.
answered Dec 19 '18 at 14:11
CS PeiCS Pei
8,4182040
Ah I see. I can perhaps use templates, although I am not sure how to solve this. I could make the structures public, and have them have a singlevoid *member to ensure "type safetyness" on the caller side.
– bartavelle
Dec 19 '18 at 14:46
add a comment |
As mentioned in the comments by @Quentin, this is a violation of ODR (one definition rule). I am not sure what your purpose is, but you can consider 2 things to meet your need. One is using a template. The other one is to use void *. but I am just guessing and hope that helps.
answered Dec 19 '18 at 14:11
CS PeiCS Pei
8,4182040
Ah I see. I can perhaps use templates, although I am not sure how to solve this. I could make the structures public, and have them have a singlevoid *member to ensure "type safetyness" on the caller side.
– bartavelle
Dec 19 '18 at 14:46
add a comment |
As mentioned in the comments by @Quentin, this is a violation of ODR (one definition rule). I am not sure what your purpose is, but you can consider 2 things to meet your need. One is using a template. The other one is to use void *. but I am just guessing and hope that helps.
answered Dec 19 '18 at 14:11
CS PeiCS Pei
8,4182040
As mentioned in the comments by @Quentin, this is a violation of ODR (one definition rule). I am not sure what your purpose is, but you can consider 2 things to meet your need. One is using a template. The other one is to use void *. but I am just guessing and hope that helps.
answered Dec 19 '18 at 14:11
CS PeiCS Pei
8,4182040
answered Dec 19 '18 at 14:11
CS PeiCS Pei
8,4182040
answered Dec 19 '18 at 14:11
CS PeiCS Pei
8,4182040
answered Dec 19 '18 at 14:11
CS PeiCS Pei
8,4182040
8,4182040
Ah I see. I can perhaps use templates, although I am not sure how to solve this. I could make the structures public, and have them have a singlevoid *member to ensure "type safetyness" on the caller side.
– bartavelle
Dec 19 '18 at 14:46
add a comment |
Ah I see. I can perhaps use templates, although I am not sure how to solve this. I could make the structures public, and have them have a singlevoid *member to ensure "type safetyness" on the caller side.
– bartavelle
Dec 19 '18 at 14:46
Ah I see. I can perhaps use templates, although I am not sure how to solve this. I could make the structures public, and have them have a single
void * member to ensure "type safetyness" on the caller side.– bartavelle
Dec 19 '18 at 14:46
Ah I see. I can perhaps use templates, although I am not sure how to solve this. I could make the structures public, and have them have a single
void * member to ensure "type safetyness" on the caller side.– bartavelle
Dec 19 '18 at 14:46
add a comment |
I would make an empty structure as a base:
// For base interface
struct _BAR {};
// For an implementation
struct Baz : BAR { ... };
In this case static_cast would do, and it will be legal C++
answered Jan 1 at 8:55
Alexander GutenevAlexander Gutenev
1,072918
add a comment |
I would make an empty structure as a base:
// For base interface
struct _BAR {};
// For an implementation
struct Baz : BAR { ... };
In this case static_cast would do, and it will be legal C++
answered Jan 1 at 8:55
Alexander GutenevAlexander Gutenev
1,072918
add a comment |
I would make an empty structure as a base:
// For base interface
struct _BAR {};
// For an implementation
struct Baz : BAR { ... };
In this case static_cast would do, and it will be legal C++
answered Jan 1 at 8:55
Alexander GutenevAlexander Gutenev
1,072918
I would make an empty structure as a base:
// For base interface
struct _BAR {};
// For an implementation
struct Baz : BAR { ... };
In this case static_cast would do, and it will be legal C++
answered Jan 1 at 8:55
Alexander GutenevAlexander Gutenev
1,072918
answered Jan 1 at 8:55
Alexander GutenevAlexander Gutenev
1,072918
answered Jan 1 at 8:55
Alexander GutenevAlexander Gutenev
1,072918
answered Jan 1 at 8:55
Alexander GutenevAlexander Gutenev
1,072918
1,072918
add a comment |
add a comment |
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2
Heads-up: you have UB here through the pointer cast, but also from the conflicting definitions of
_BARwhich violate ODR. I think you're knee-deep in a solution which won't pan out.– Quentin
Dec 19 '18 at 14:05
1
each implementation defines its own struct?
_BARhas to be always the same type, and you cannot define the same type more than once– user463035818
Dec 19 '18 at 14:05
Alright, I went with a distinct solution. Is this question useful or should I just delete it?
– bartavelle
Dec 19 '18 at 15:19