Re: [boost] [x-files][singleton] incomplete type problem

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2007-12-03 01:55:30

Michael,

Michael Marcin wrote:
> I ran into a compiler problem using the singleton library from the vault.
> 
> singleton's constructor and destructor use instance_proxy before it is 
> defined. The trivial fix is to make the definition of the constructor 
> and destructor inline function at the bottom of the file (i.e. after 
> instance_proxy is defined).

Actually, that shouldn't be a problem since 'singleton' is a template 
and things are complete once it's instantiated.

Got some code that fails to compile?

> 
> singleton_manager.hpp causes warning under msvc 8.0 in the 
> singleton_manager::cleanup function:
> 
>   warning C4706: assignment within conditional expression
> 
> for
> 
> while (!!(i = ptr_instance->ptr_first))
> 
> if this could be rewritten without much effort to silence the warning it 
> would be nice.

Yes (where interestingly the compiler could figure out this is not a 
typo here because of the '!!')...

Maybe

     while ((i = ptr_instance->ptr_first) != 0l)

will do the trick...

> 
> Nit - there seems to be a lot of extraneous inline keywords for 
> functions defined inside the class definition.

...intentionally, because some compilers (under certain configurations) 
distinguish between "implicit" inline and "inline by keyword".

> 
> 
> The library has proven quite useful.
> 

Thanks for your feedback.

Regards,
Tobias