[Bug c++/45082] Static const signed int class member causes undefined symbol.

["redi at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #6 from redi at gcc dot gnu dot org  2010-07-27 23:54 -------
(In reply to comment #5)
> Thanks for all the great comments and insight.
> 
> I'm still confused as to why when the BUFF_SIZE was defined as:
> static const   signed int BUFF_SIZE = 20;
> it caused the error, but when it was defined as:
> static const unsigned int BUFF_SIZE = 20;
> it did not.

Because you can't bind const int& to an unsigned int, so a temporary is created
and the reference bound to that.  When the variable has type int the reference
can bind to it directly.


> There were 2 things that solved the problem I was seeing:
> 
> 1. Adding a const   signed int BUFF_SIZE; line to the .cpp file.  
> 
> I've seen lots of code where we define constants ala, static const int
> BUFF_SIZE=20; in the .hpp file without any const int myclass::BUFF_SIZE; in the
> .cpp files.  Is that wrong to exclude them, should we be including them in the
> .cpp file?

Yes, if the variable is "used" in the program, see the reference from the
standard that Jakub posted days ago in comment 1

> 2. Declaring the type during the call, ala, funky((int)myclass::BUFF_SIZE);

You might have misunderstood that as well, there's no "declaring the type"
there, it's creating a temporary which the reference binds to.

> I'm not sure which is the better solution.

Again, please follow up somewhere else, GCC's bugzilla is not the right place
to learn the rules of C++.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45082