[Bug c/20655] Attempt to use undefined structure tag triggers no diagnostic

[jozef dot behran at krs dot sk]

--- Additional Comments From jozef dot behran at krs dot sk  2005-04-01 
19:49 ---
 This is still valid code because the struct could be defined below still. 
 
But if the struct is not defined anywhere (not even below its use), a warning 
should 
occur. If you send the first declaration to the compiler without sending the 
second 
one, you should see a warning about an undeclared structure. However if you 
send your example to the compiler as you mentioned it, no warnings should 
appear. This warning should at least indicate the users that there may be 
something wrong with their code and that they should check for typos or so. 
Note that the code is valid, but unusual. If you see a structure tag used 
somewhere without being declared, most likely it is a bug in the code. 
Otherwise 
the compiler may give the user very strange error/warning messages that may 
confuse him seriously (a structure type seeming not to be compatible with 
itself). 

-- 
   What|Removed |Added

 Status|RESOLVED|UNCONFIRMED
 Resolution|INVALID |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20655

[Bug c/20655] Attempt to use undefined structure tag triggers no diagnostic

[joseph at codesourcery dot com]

--- Additional Comments From joseph at codesourcery dot com  2005-04-01 
20:19 ---
Subject: Re:  Attempt to use undefined structure tag triggers
 no diagnostic

On Fri, 1 Apr 2005, jozef dot behran at krs dot sk wrote:

 Note that the code is valid, but unusual. If you see a structure tag used 
 somewhere without being declared, most likely it is a bug in the code. 
 Otherwise 

No, if a tag is used without the structure or union contents being defined 
then most likely it is being used as an opaque type and the definition is 
in a separate internal header for e.g. the library implementation but does 
not form part of the public interface.



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20655

[Bug c/20655] Attempt to use undefined structure tag triggers no diagnostic

[pinskia at gcc dot gnu dot org]

--- Additional Comments From pinskia at gcc dot gnu dot org  2005-04-01 
20:58 ---
If you deference or do an assignment like:

TType *a, *b;

b-Pointer = a;

You will either get an error or a warning saying the code is invalid.

Also as mentioned by JSM, it is a way to provide opaque type pointers.

-- 
   What|Removed |Added

 Status|UNCONFIRMED |RESOLVED
 Resolution||WONTFIX


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20655

[Bug c/20655] Attempt to use undefined structure tag triggers no diagnostic

[pinskia at gcc dot gnu dot org]

--- Additional Comments From pinskia at gcc dot gnu dot org  2005-03-27 
16:15 ---
This is still valid code because the struct could be defined below still.
For an example:
struct a
{
  struct b *c;
};

struct b
{
  int i;
  struct a *c;
};

-- 
   What|Removed |Added

 Status|UNCONFIRMED |RESOLVED
 Resolution||INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20655