Re: Boost 1.25.0 build problems?

From: williamkempf_at_[hidden]
Date: 2001-10-04 14:30:38

--- In boost_at_y..., Beman Dawes <bdawes_at_a...> wrote:
> At 01:08 PM 10/4/2001, Peter Dimov wrote:
> 
>  >From: <williamkempf_at_h...>
>  >> > Looks like basic_string is only fwd declared at his point.
>  >>
>  >> I'm not sure if STLPort is compliant here or not, but this 
causes
>  >> grief.  The standard explicitly says that the std::exception 
types
>  >> should all take an argument of type "const string&" in their
>  >> constructors.  The fact that the type is a reference may allow
>  >> implementations to only forward declare std::string here, but 
doing
>  >> so is a questionable practice as it doesn't accomplish much of
>  >> anything.  Any code that constructs a std::exception type is 
going to
>  >> have to include <string> any way, so very few compilation units 
will
>  >> benefit from the "optimization".  It won't hurt for me to 
include
>  >> <string> in <boost/thread/exceptions>, but I really question 
why I
>  >> should have to.
>  >
>  >Because the standard says so. If you use std::string, you have to 
> #include
>  ><string>. Other headers are not required to do it for you, even 
when 
> their
>  >interfaces mention std::string.
> 
> That's my reading too.  IIRC, it is also one of the examples Andy 
Koenig 
> gives of why the current rules can lead to user confusion.
> 
> My reading of the rules is that if a standard library header 
requires a 
> definition of a type (presumably because it needs a complete type), 
the 
> appropriate standard library header has to be included by the 
> implementation.  But if only a declaration is required (because the 
usage 
> is such an incomplete type is OK), the full header doesn't have to 
be 
> included.

Well, I suspected that technically it was compliant, but regardless I 
view this as a QoI issue.  There's such little benefit gained by 
forward declaring std::string in this case that it's a pain to 
require its inclusion.  The current case is a great example of why I 
feel this way.  None of the Boost.Threads code uses std::string at 
all, so I should not be required to include it myself just because I 
use std::exception types.

Bill Kempf