[Bug c++/21146] unable to resolve visible symbol

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=21146

Jonathan Wakely  changed:

   What|Removed |Added

   See Also||https://gcc.gnu.org/bugzill
   ||a/show_bug.cgi?id=13590
   Last reconfirmed|2009-02-07 20:18:28 |2020-8-26
 Blocks|65608   |94404

--- Comment #7 from Jonathan Wakely  ---
(In reply to Manuel López-Ibáñez from comment #4)
> Do we know how icc resolves the ambiguity?

I assume it checks that the two lookup results for "S" actually name the same
type, and so decides there's no ambiguity.

I think that is correct according to [class.member.lookup]. The declaration
sets for lookup of S in ::C and in ::B and in :S and in ::A<::S> all find the
same type, ::S. So there is no ambiguity.

This was ambiguous in C++03 but that was changed by CWG 39
http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#39

So GCC is wrong.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65608
[Bug 65608] [meta-bug] friend issues
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94404
[Bug 94404] [meta-bug] C++ core issues

[Bug c++/21146] unable to resolve visible symbol

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=21146

--- Comment #6 from Jonathan Wakely  ---
EDG still accepts this, but Clang doesn't:

21146.cc:13:18: error: member 'S' found in multiple base classes of different
types
  friend class A;
 ^
21146.cc:7:8: note: member found by ambiguous name lookup
struct S {};
   ^
21146.cc:4:13: note: member found by ambiguous name lookup
  typedef T S;
^
21146.cc:13:18: error: member 'S' found in multiple base classes of different
types
  friend class A;
 ^
21146.cc:7:8: note: member found by ambiguous name lookup
struct S {};
   ^
21146.cc:4:13: note: member found by ambiguous name lookup
  typedef T S;
^
2 errors generated.


I think GCC and Clang are right here.

[Bug c++/21146] unable to resolve visible symbol

[manu at gcc dot gnu dot org]

--- Comment #5 from manu at gcc dot gnu dot org  2009-02-07 20:18 ---
This still fails in GCC 4.4

icc accepts the code in strict mode, so I guess this is rejects-valid.


-- 

manu at gcc dot gnu dot org changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
 Ever Confirmed|0   |1
   Keywords||rejects-valid
  Known to fail||4.4.0
   Last reconfirmed|-00-00 00:00:00 |2009-02-07 20:18:28
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21146

[Bug c++/21146] unable to resolve visible symbol

[manu at gcc dot gnu dot org]

--- Comment #4 from manu at gcc dot gnu dot org  2007-11-15 16:30 ---
So, is this a bug or not? Do we know how icc resolves the ambiguity?


-- 

manu at gcc dot gnu dot org changed:

   What|Removed |Added

 CC||manu at gcc dot gnu dot org
   Keywords||diagnostic


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21146

[Bug c++/21146] unable to resolve visible symbol

[reichelt at gcc dot gnu dot org]

--- Comment #3 from reichelt at gcc dot gnu dot org  2007-04-09 18:32 
---
Btw, since GCC 4.1.0 the error message is:

bug.cc:13: error: reference to 'S' is ambiguous
bug.cc:4: error: candidates are: typedef struct S AS::S
bug.cc:7: error: struct S
bug.cc:13: error: template argument 1 is invalid
bug.cc:13: error: friend declaration does not name a class or function


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21146

[Bug c++/21146] unable to resolve visible symbol

[bangerth at dealii dot org]

--- Additional Comments From bangerth at dealii dot org  2005-05-02 18:54 
---
What is going wrong is this: the name 'S' may refer to both the local 
typedef in the base class 'A' as well as to the global structure '::S'. 
If I write either 
  friend class A A ::S::S; 
or  
  friend class A ::S; 
then the code is accepted by gcc. 
 
I don't know whether the ambiguity makes the code invalid. As a reference 
point, icc accepts the code in strict mode. 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21146

[Bug c++/21146] unable to resolve visible symbol

[pinskia at gcc dot gnu dot org]

--- Additional Comments From pinskia at gcc dot gnu dot org  2005-04-21 
12:59 ---
3.3.3 gave:
t.cc:13: error: request for member `S' is ambiguous in multiple inheritance 
   lattice
t.cc:7: error: candidates are: struct S
t.cc:4: error: typedef struct S AS::S
t.cc:13: error: template argument 1 is invalid
t.cc:13: error: ISO C++ forbids declaration of `type name' with no type

If the code is invalid, then we have a diagnostic regression.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21146