Re: [Boost-bugs] [Boost C++ Libraries] #3729: boost.log and 1.41.0 : external linkage error

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #3729: boost.log and 1.41.0 : external linkage error
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-01-29 19:19:06

#3729: boost.log and 1.41.0 : external linkage  error
-----------------------------------------+----------------------------------
  Reporter:  lb <lburgazzoli@…>          |       Owner:  igaztanaga
      Type:  Bugs                        |      Status:  closed    
 Milestone:  Boost 1.42.0                |   Component:  intrusive 
   Version:  Boost 1.41.0                |    Severity:  Problem   
Resolution:  invalid                     |    Keywords:            
-----------------------------------------+----------------------------------
Changes (by andysem):

  * status:  new => closed
  * resolution:  => invalid

Comment:

 From the Boost developers ML:

 > The combination of gcc version (gcc 4.2.x), the reported error reason
 > (has not external linkage) and the type in the error location
 > including names in an anonymous namespace (occurrences of<unnamed>)
 > lead me to believe this is the same as a problem I've encountered a
 > number of times, most recently yesterday.
 >
 > The issue seems to be that gcc 4.2 contains (the beginnings of?) an
 > optimization to exclude symbols from anonymous namespaces from the set
 > of external linker symbols, as a space optimization, and possibly with
 > other benefits. Unfortunately, in gcc 4.2 this seems to have been
 > somewhat botched because these symbols still need to be treated as
 > having external linkage as far as various C++ language features are
 > concerned, and that doesn't appear to be done correctly. These
 > problems seem to have been addressed in gcc 4.3.
 >
 > The only workaround I've found for this is to change the relevant
 > anonymous namespace to be a named namespace, typically some "detail"
 > or "impl" type of namespace since these aren't supposed to be public
 > names. I've only encountered this problem with gcc 4.2.x; 4.1 doesn't
 > have the (attempt at) the relevant optimization, and this problem
 > seems to have been fixed in gcc 4.3.

 -- Kim Barrett

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/3729#comment:1>
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