If you specify an allocator in an STL container is it a requirement that
the allocator allocates object of the right type, or can you assume that
the container will rebind the allocator to the correct type?
For example I tried the following code which uses a 'wrong' allocator and
was slightly surrised to find it compiles on the three compilers I tried
it on
#include <vector>
#include <memory>
int main()
{
std::vector<int , std::allocator< double> > vec;
vec.push_back(1 );
}
john
Jul 22 '05
13  1952 
Jonathan Turkanis wrote: "John Harrison" <jo************ *@hotmail.com> wrote in message
news:opsav3hke1 212331@andronic us...
On Fri, 9 Jul 2004 15:21:25 -0600, Jonathan Turkanis
<te******@kan garoologic.com> wrote:
"John Harrison" <jo************ *@hotmail.com> wrote in message
news:opsav1x fa5212331@andro nicus... [...]I also noticed that Josuttis' book also ignores what the standard
says,
see first page of chapter 15 where he happily passes the same
allocator to
several containers with different value types.
It looks to me like the allocators he uses all have value_types
appropriat e for the containers.
Well maybe I'm reading too much into this but in chpater 15 in quick
succession he gives
vector<int,Sp ecialAlloc> v;
map<int,float ,less<int>,Spec ialAlloc> m;
basic_string< char,char_trait s<char>,Special Alloc> s;
That's funny. My copy has
vector<int, MyAlloc<int> > v;
map<int,float,l ess<int>,MyAllo c<std::pair<con st int, float> > > m;
...
<Butting in...>
So does mine, but it's the 7th printing (what's yours?) so, either
before they printed something differently or after...
V
"Victor Bazarov" <v.********@com Acast.net> wrote in message
news:uv******** *********@ord-read.news.verio .net... Jonathan Turkanis wrote: "John Harrison" <jo************ *@hotmail.com> wrote in message
news:opsav3hke1 212331@andronic us...
Well maybe I'm reading too much into this but in chpater 15 in
quicksuccession he gives
vector<int,Sp ecialAlloc> v;
map<int,float ,less<int>,Spec ialAlloc> m;
basic_string< char,char_trait s<char>,Special Alloc> s;
That's funny. My copy has
vector<int, MyAlloc<int> > v;
map<int,float,l ess<int>,MyAllo c<std::pair<con st int, float> > >
m; ...
<Butting in...>
So does mine, but it's the 7th printing (what's yours?) so, either
before they printed something differently or after...
Mine is the 10th. I wonder if Josuttis changed it because he decided
it was an error or because he thought it was debatable or an
unnecessary distraction.
I'm a bit suprised that the requirement that the value_type's match is
stated clearly for basic_string (21.3/1) but only in an almost
parenthetical way for containers generally (23.1/8), AFAICT.
Jonathan
>> Yes it seems so, both implementations of the STL I've checked do rebind
the allocator for vector at least. This seems to directly contradict the
requirements for allocator_type.
I think this approach gives meaning to an otherwise ill formed program,
hence it's a conforming implementation.
Yes, thinking about it I agree.
john
On Fri, 9 Jul 2004 16:13:19 -0600, Jonathan Turkanis
<te******@kanga roologic.com> wrote:
Mine is the 10th. I wonder if Josuttis changed it because he decided
it was an error or because he thought it was debatable or an
unnecessary distraction.
Mine's the third, the change is listed in the errata on his website.
john This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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