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

[Paolo Carlini <pcarlini at unitus dot it>]

The following reply was made to PR libstdc++/9626; it has been noted by GNATS.

From: Paolo Carlini <pcarlini@unitus.it>
To: Cc: Falk Hueffner <falk.hueffner@student.uni-tuebingen.de>, 
 gcc-bugs@gcc.gnu.org,  gcc-gnats@gcc.gnu.org
Subject: Re: libstdc++/9626: g++ accepts vector<vector<int> > v(2, 4);
Date: Sat, 08 Feb 2003 16:28:16 +0100

 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