Re: c++/10541: Is NULL a valid pointer-type template argument?

[Gianni Mariani <gianni at mariani dot ws>]

Wolfgang Bangerth wrote:

> > I remember reading a while back that C/C++ considers the value 0 to be a 
> > valid value for any pointer type.  Hence 0 CAN BE of type char *.
> >    
>
> Well, 0 is of type "signed int". It can be converted to any pointer type 
> implicitly. The question is whether the compiler is supposed to do 
> implicit conversions for template args. I don't think so.
>
>  
>
> > Other compilers seem to take this value.
> >    
>
> icc doesn't, for example.
>  
   In this posting:
   news://nntp.concentric.net:119/vatbv4b1hbd6d3 at corp dot supernews dot com
   http://groups.google.com/groups?dq=&hl=en&lr=&ie=UTF-8&threadm=b8m2ve%243h4%40dispatch.concentric.net&prev=/groups%3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26group%3Dcomp.lang.c%252B%252B

> According to 14.3.2/1 a pointer template argument must be a pointer to
> > an object with external linkage. 0 is certainly not such a pointer.
> >
> > Generally, you'll need
> >
> > IType<char*, someexternarrayname>
> > or
> > IType<char*, &someexternchar>
> >
> > Apparently, Comeau gets this wrong, allowing IType<char *,
> > static_cast<char *>(0)>.
>    

   There is an open issue 354 on this, BTW. I would think that
   Comeau is just running ahead of the pack (along with EDG, MS,
   Borland, and Cfront -- as described in the issue). Gcc and
   Sun are the pack.

Seems like this is an open issue.