Re: [boost] Re: [assign] fixes for msvc, msvc-stlport and vc7

From: JOAQUIN LOPEZ MU?Z (joaquin_at_[hidden])
Date: 2004-09-21 15:08:56

----- Mensaje original -----
De: Thorsten Ottosen <nesotto_at_[hidden]>
Fecha: Martes, Septiembre 21, 2004 9:03 pm
Asunto: [boost] Re: [assign] fixes for msvc, msvc-stlport and vc7

> Hi Joaquin,
> 
[...]
> 
> | 2. list_insert::operator()(T t) has been changed to accept
> | a const reference instead.
> 
> I have made this change as
> 
> #if BOOST_WORKAROUND(BOOST_MSVC, <= 1200)
> 
>        template< class T >
>        list_inserter& operator()( const T& t )
> #else
>        template< class T >
>        list_inserter& operator()( T t )
> #endif

As you wrote it, the workaround applies only to
MSVC 6.0. Let's wait for the next test cycle to see 
if it has to be extended to MSVC 7.0 as well.

> 
> | With these changes, all tests build, though three of them
> | crash at run-time (list_inserter, list_of and multi_index_container)
> 
> ok, this is much better than before! some of the test a big and 
> fat and do
> some tricky conversions...but just having the
> basic stuff working is great!
> 
> |I've got two questions:
> |
> |1. Could somebody (the author, I guess) validate these changes
> |for commit?
> 
> I have comitted them.
> 
> |2. list_inserter follows a strange convention (IMHO) of not
> |forcing template params to be const references in its various
> |copy ctors and assignment operators, for instance:
> |
> |list_inserter( Function fun );
> |template< class T >
> |list_inserter& operator=( T r );
> |
> |Any reason for this approach? I don't know if this can pose
> |problems, but to me having these qualified with const & seems
> |like the usual way.
> 
> yes, the bitches are char[N] and wchar_t[N] which does not convert 
> to char*
> and wchar_t* otherwise. this comes up in simple stuff like
> 
> vector<string> = list_of( "foo" )( "goobar" );

Ummm, I see. The fact is that here lies, I think, the reason
for the three remaining crashes, all on calls to multi-argument
versions of list_inserter::operator().
Maybe I'll give this some thinking over if I have some spare
time tomorrow.

> 
> of course, the Function arg could be const Function&, but is there any
> difference in inline code?

I think this can involve an extra copy under some circumstances,
ans some compilers might not optimize this away. But in general
I agree with you little is gained by having const Function &.

> 
> Muchos gracias for the patch!

Velbekomme :)

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo