Class inaccessible after inheritance
If you compile the code below it fails, saying that class B is inaccessible where it is used as an argument to the member function func. Why is this?
Note: if D2 does not inherit from D1 then the error goes away, so somehow the inheritance from D2 makes B inaccessible.
namespace myns {
class B {};
}
using namespace myns;
class D1 : B {};
class D2 : D1 {
void func(B b) {}
};
c++ namespaces
edited Dec 30 '18 at 17:16
Baum mit Augen
41k12118152
asked Sep 5 '13 at 3:21
MatMat
8719
add a comment |
If you compile the code below it fails, saying that class B is inaccessible where it is used as an argument to the member function func. Why is this?
Note: if D2 does not inherit from D1 then the error goes away, so somehow the inheritance from D2 makes B inaccessible.
namespace myns {
class B {};
}
using namespace myns;
class D1 : B {};
class D2 : D1 {
void func(B b) {}
};
c++ namespaces
edited Dec 30 '18 at 17:16
Baum mit Augen
41k12118152
asked Sep 5 '13 at 3:21
MatMat
8719
You did a fantastic job of obfuscating your own question by the simple omission of the actual compile error. stackoverflow.com/questions/how-to-ask
– kfsone
Sep 5 '13 at 5:25
add a comment |
If you compile the code below it fails, saying that class B is inaccessible where it is used as an argument to the member function func. Why is this?
Note: if D2 does not inherit from D1 then the error goes away, so somehow the inheritance from D2 makes B inaccessible.
namespace myns {
class B {};
}
using namespace myns;
class D1 : B {};
class D2 : D1 {
void func(B b) {}
};
c++ namespaces
edited Dec 30 '18 at 17:16
Baum mit Augen
41k12118152
asked Sep 5 '13 at 3:21
MatMat
8719
If you compile the code below it fails, saying that class B is inaccessible where it is used as an argument to the member function func. Why is this?
Note: if D2 does not inherit from D1 then the error goes away, so somehow the inheritance from D2 makes B inaccessible.
namespace myns {
class B {};
}
using namespace myns;
class D1 : B {};
class D2 : D1 {
void func(B b) {}
};
c++ namespaces
c++ namespaces
edited Dec 30 '18 at 17:16
Baum mit Augen
41k12118152
asked Sep 5 '13 at 3:21
MatMat
8719
edited Dec 30 '18 at 17:16
Baum mit Augen
41k12118152
asked Sep 5 '13 at 3:21
MatMat
8719
edited Dec 30 '18 at 17:16
Baum mit Augen
41k12118152
edited Dec 30 '18 at 17:16
Baum mit Augen
41k12118152
edited Dec 30 '18 at 17:16
Baum mit Augen
41k12118152
41k12118152
asked Sep 5 '13 at 3:21
MatMat
8719
asked Sep 5 '13 at 3:21
MatMat
8719
asked Sep 5 '13 at 3:21
MatMat
8719
8719
You did a fantastic job of obfuscating your own question by the simple omission of the actual compile error. stackoverflow.com/questions/how-to-ask
– kfsone
Sep 5 '13 at 5:25
add a comment |
You did a fantastic job of obfuscating your own question by the simple omission of the actual compile error. stackoverflow.com/questions/how-to-ask
– kfsone
Sep 5 '13 at 5:25
You did a fantastic job of obfuscating your own question by the simple omission of the actual compile error. stackoverflow.com/questions/how-to-ask
– kfsone
Sep 5 '13 at 5:25
You did a fantastic job of obfuscating your own question by the simple omission of the actual compile error. stackoverflow.com/questions/how-to-ask
– kfsone
Sep 5 '13 at 5:25
add a comment |
3 Answers
3
active
oldest
votes
Name lookup finds D2::D1::B, not myns::B. After name lookup, access check is performed, and discovers that D2::D1::B is private.
The namespace is a red herring: the exact same outcome is observed if B is defined in the global namespace.
answered Sep 5 '13 at 3:31
Igor TandetnikIgor Tandetnik
32.3k33456
add a comment |
You need to add the :: operator. Lookup is finding the injected-class-name instead of the myns::B.
class D2 : D1 {
void func(::B b) {}
};
11.1p5
5 [ Note: In a derived class, the lookup of a base class name will
find the injected-class-name instead of the name of the base class in
the scope in which it was declared. The injected-class-name might be
less accessible than the name of the base class in the scope in which
it was declared. —end note ]
[Example:
class A { };
class B : private A { };
class C : public B {
A *p; // error: injected-class-name A is inaccessible
::A *q; // OK
};
answered Sep 5 '13 at 3:31
Jesse GoodJesse Good
38.1k1086141
1
I'm very interesting why we need class name injection? What the problem it want to solve, any code example?
– ZijingWu
Sep 5 '13 at 8:06
1
@ZijingWu: Here is one example, would you rather write functionf1orf2? The injected-class-name makesA f2() {return A();}possible.
– Jesse Good
Sep 5 '13 at 9:52
so injected-class-name is try to make reference class template easier? And even in this case why the base class name also be injected into the scope, which cause a lot of confusing like this post, I see the same question more than once in SO.
– ZijingWu
Sep 5 '13 at 10:04
add a comment |
The default access specifier when inheriting a class/struct is "private", so your problem is this:
class D1 : B {};
class D2 : D1 {};
Add the keyword "public" and voila.
http://ideone.com/T5RpUM
namespace myns {
class B {};
}
using namespace myns;
class D1 : public B {};
class D2 : public D1 {
void func(B b) {}
};
int main() {
D2 d();
}
answered Sep 5 '13 at 5:28
kfsonekfsone
19k22655
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
Name lookup finds D2::D1::B, not myns::B. After name lookup, access check is performed, and discovers that D2::D1::B is private.
The namespace is a red herring: the exact same outcome is observed if B is defined in the global namespace.
answered Sep 5 '13 at 3:31
Igor TandetnikIgor Tandetnik
32.3k33456
add a comment |
Name lookup finds D2::D1::B, not myns::B. After name lookup, access check is performed, and discovers that D2::D1::B is private.
The namespace is a red herring: the exact same outcome is observed if B is defined in the global namespace.
answered Sep 5 '13 at 3:31
Igor TandetnikIgor Tandetnik
32.3k33456
add a comment |
Name lookup finds D2::D1::B, not myns::B. After name lookup, access check is performed, and discovers that D2::D1::B is private.
The namespace is a red herring: the exact same outcome is observed if B is defined in the global namespace.
answered Sep 5 '13 at 3:31
Igor TandetnikIgor Tandetnik
32.3k33456
Name lookup finds D2::D1::B, not myns::B. After name lookup, access check is performed, and discovers that D2::D1::B is private.
The namespace is a red herring: the exact same outcome is observed if B is defined in the global namespace.
answered Sep 5 '13 at 3:31
Igor TandetnikIgor Tandetnik
32.3k33456
answered Sep 5 '13 at 3:31
Igor TandetnikIgor Tandetnik
32.3k33456
answered Sep 5 '13 at 3:31
Igor TandetnikIgor Tandetnik
32.3k33456
answered Sep 5 '13 at 3:31
Igor TandetnikIgor Tandetnik
32.3k33456
32.3k33456
add a comment |
add a comment |
You need to add the :: operator. Lookup is finding the injected-class-name instead of the myns::B.
class D2 : D1 {
void func(::B b) {}
};
11.1p5
5 [ Note: In a derived class, the lookup of a base class name will
find the injected-class-name instead of the name of the base class in
the scope in which it was declared. The injected-class-name might be
less accessible than the name of the base class in the scope in which
it was declared. —end note ]
[Example:
class A { };
class B : private A { };
class C : public B {
A *p; // error: injected-class-name A is inaccessible
::A *q; // OK
};
answered Sep 5 '13 at 3:31
Jesse GoodJesse Good
38.1k1086141
1
I'm very interesting why we need class name injection? What the problem it want to solve, any code example?
– ZijingWu
Sep 5 '13 at 8:06
1
@ZijingWu: Here is one example, would you rather write functionf1orf2? The injected-class-name makesA f2() {return A();}possible.
– Jesse Good
Sep 5 '13 at 9:52
so injected-class-name is try to make reference class template easier? And even in this case why the base class name also be injected into the scope, which cause a lot of confusing like this post, I see the same question more than once in SO.
– ZijingWu
Sep 5 '13 at 10:04
add a comment |
You need to add the :: operator. Lookup is finding the injected-class-name instead of the myns::B.
class D2 : D1 {
void func(::B b) {}
};
11.1p5
5 [ Note: In a derived class, the lookup of a base class name will
find the injected-class-name instead of the name of the base class in
the scope in which it was declared. The injected-class-name might be
less accessible than the name of the base class in the scope in which
it was declared. —end note ]
[Example:
class A { };
class B : private A { };
class C : public B {
A *p; // error: injected-class-name A is inaccessible
::A *q; // OK
};
answered Sep 5 '13 at 3:31
Jesse GoodJesse Good
38.1k1086141
1
I'm very interesting why we need class name injection? What the problem it want to solve, any code example?
– ZijingWu
Sep 5 '13 at 8:06
1
@ZijingWu: Here is one example, would you rather write functionf1orf2? The injected-class-name makesA f2() {return A();}possible.
– Jesse Good
Sep 5 '13 at 9:52
so injected-class-name is try to make reference class template easier? And even in this case why the base class name also be injected into the scope, which cause a lot of confusing like this post, I see the same question more than once in SO.
– ZijingWu
Sep 5 '13 at 10:04
add a comment |
You need to add the :: operator. Lookup is finding the injected-class-name instead of the myns::B.
class D2 : D1 {
void func(::B b) {}
};
11.1p5
5 [ Note: In a derived class, the lookup of a base class name will
find the injected-class-name instead of the name of the base class in
the scope in which it was declared. The injected-class-name might be
less accessible than the name of the base class in the scope in which
it was declared. —end note ]
[Example:
class A { };
class B : private A { };
class C : public B {
A *p; // error: injected-class-name A is inaccessible
::A *q; // OK
};
answered Sep 5 '13 at 3:31
Jesse GoodJesse Good
38.1k1086141
You need to add the :: operator. Lookup is finding the injected-class-name instead of the myns::B.
class D2 : D1 {
void func(::B b) {}
};
11.1p5
5 [ Note: In a derived class, the lookup of a base class name will
find the injected-class-name instead of the name of the base class in
the scope in which it was declared. The injected-class-name might be
less accessible than the name of the base class in the scope in which
it was declared. —end note ]
[Example:
class A { };
class B : private A { };
class C : public B {
A *p; // error: injected-class-name A is inaccessible
::A *q; // OK
};
answered Sep 5 '13 at 3:31
Jesse GoodJesse Good
38.1k1086141
edited Sep 5 '13 at 3:37
answered Sep 5 '13 at 3:31
Jesse GoodJesse Good
38.1k1086141
answered Sep 5 '13 at 3:31
Jesse GoodJesse Good
38.1k1086141
answered Sep 5 '13 at 3:31
Jesse GoodJesse Good
38.1k1086141
38.1k1086141
1
I'm very interesting why we need class name injection? What the problem it want to solve, any code example?
– ZijingWu
Sep 5 '13 at 8:06
1
@ZijingWu: Here is one example, would you rather write functionf1orf2? The injected-class-name makesA f2() {return A();}possible.
– Jesse Good
Sep 5 '13 at 9:52
so injected-class-name is try to make reference class template easier? And even in this case why the base class name also be injected into the scope, which cause a lot of confusing like this post, I see the same question more than once in SO.
– ZijingWu
Sep 5 '13 at 10:04
add a comment |
1
I'm very interesting why we need class name injection? What the problem it want to solve, any code example?
– ZijingWu
Sep 5 '13 at 8:06
1
@ZijingWu: Here is one example, would you rather write functionf1orf2? The injected-class-name makesA f2() {return A();}possible.
– Jesse Good
Sep 5 '13 at 9:52
so injected-class-name is try to make reference class template easier? And even in this case why the base class name also be injected into the scope, which cause a lot of confusing like this post, I see the same question more than once in SO.
– ZijingWu
Sep 5 '13 at 10:04
1
1
I'm very interesting why we need class name injection? What the problem it want to solve, any code example?
– ZijingWu
Sep 5 '13 at 8:06
I'm very interesting why we need class name injection? What the problem it want to solve, any code example?
– ZijingWu
Sep 5 '13 at 8:06
1
1
@ZijingWu: Here is one example, would you rather write function
f1 or f2? The injected-class-name makes A f2() {return A();} possible.– Jesse Good
Sep 5 '13 at 9:52
@ZijingWu: Here is one example, would you rather write function
f1 or f2? The injected-class-name makes A f2() {return A();} possible.– Jesse Good
Sep 5 '13 at 9:52
so injected-class-name is try to make reference class template easier? And even in this case why the base class name also be injected into the scope, which cause a lot of confusing like this post, I see the same question more than once in SO.
– ZijingWu
Sep 5 '13 at 10:04
so injected-class-name is try to make reference class template easier? And even in this case why the base class name also be injected into the scope, which cause a lot of confusing like this post, I see the same question more than once in SO.
– ZijingWu
Sep 5 '13 at 10:04
add a comment |
The default access specifier when inheriting a class/struct is "private", so your problem is this:
class D1 : B {};
class D2 : D1 {};
Add the keyword "public" and voila.
http://ideone.com/T5RpUM
namespace myns {
class B {};
}
using namespace myns;
class D1 : public B {};
class D2 : public D1 {
void func(B b) {}
};
int main() {
D2 d();
}
answered Sep 5 '13 at 5:28
kfsonekfsone
19k22655
add a comment |
The default access specifier when inheriting a class/struct is "private", so your problem is this:
class D1 : B {};
class D2 : D1 {};
Add the keyword "public" and voila.
http://ideone.com/T5RpUM
namespace myns {
class B {};
}
using namespace myns;
class D1 : public B {};
class D2 : public D1 {
void func(B b) {}
};
int main() {
D2 d();
}
answered Sep 5 '13 at 5:28
kfsonekfsone
19k22655
add a comment |
The default access specifier when inheriting a class/struct is "private", so your problem is this:
class D1 : B {};
class D2 : D1 {};
Add the keyword "public" and voila.
http://ideone.com/T5RpUM
namespace myns {
class B {};
}
using namespace myns;
class D1 : public B {};
class D2 : public D1 {
void func(B b) {}
};
int main() {
D2 d();
}
answered Sep 5 '13 at 5:28
kfsonekfsone
19k22655
The default access specifier when inheriting a class/struct is "private", so your problem is this:
class D1 : B {};
class D2 : D1 {};
Add the keyword "public" and voila.
http://ideone.com/T5RpUM
namespace myns {
class B {};
}
using namespace myns;
class D1 : public B {};
class D2 : public D1 {
void func(B b) {}
};
int main() {
D2 d();
}
answered Sep 5 '13 at 5:28
kfsonekfsone
19k22655
answered Sep 5 '13 at 5:28
kfsonekfsone
19k22655
answered Sep 5 '13 at 5:28
kfsonekfsone
19k22655
answered Sep 5 '13 at 5:28
kfsonekfsone
19k22655
19k22655
add a comment |
add a comment |
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You did a fantastic job of obfuscating your own question by the simple omission of the actual compile error. stackoverflow.com/questions/how-to-ask
– kfsone
Sep 5 '13 at 5:25