libstdc++/9626: g++ accepts vector<vector<int> > v(2, 4);

[Paolo Carlini]

Well... really interesting.

I found a *very* interesting interchange on C++-moderated back in 
May-2002, between John Potter, Carlos Moreno and others:

http://groups.google.it/groups?hl=it&lr=&ie=UTF-8&threadm=3cf85a1f.17498620%40news.earthlink.net&rnum=40&prev=/groups%3Fq%3Dvector%253Cvector%2Bgroup:comp.*%26start%3D30%26hl%3Dit%26lr%3D%26ie%3DUTF-8%26selm%3D3cf85a1f.17498620%2540news.earthlink.net%26rnum%3D40 


It ends with them _agreeing_ that the syntax is _legal_ and John 
replying to another guy:

> > When people ask me what the keyword 'explicit' is for I usually take a
> > vector in particular as an example: > Speaking of std::vector it has 
> > explicit vector(size_type n, const T& value = T(),
> >              const Allocator& = Allocator()); > so I'd expect that > 
> vector< vector<int> > values (20, 30); 
> > must NOT compile on a conformant implementation.
>
> However, 20 is not a size_type and it does not match that constructor.
> It matches
>
> template <class InputIterator>
> vector (InputIterator first, InputIterator last,
>       Allocator const& = Allocator());
>
> Since int can't be an iterator, the implementation is required to make
> it act the same as
>
> vector(static_cast<size_type>(first), static_cast<value_type>(last));
>
> The second static_cast takes care of your concerns about explicit.
>
> See 23.1.1/9
>
> John

At this point I think we can safely close the report!
Paolo.





http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9626