Re: [boost] auto-link with gcc/windows

Subject: Re: [boost] auto-link with gcc/windows
From: Robert Ramey (ramey_at_[hidden])
Date: 2010-07-06 04:12:38

Jürgen Hunold wrote:
> Hi Robert,
>
> On Tuesday, 6. July 2010 00:07:48 you wrote:
>> Jürgen Hunold wrote:
>>> BOOST_HAS_DECLSPEC is the interesting one.
>>> Please find a patch adding two more "#define
>>> BOOST_SERIALIZATION_SOURCE" to the sources. This fixed compilation
>>> for me when using gcc's symbol visibility and might help here as
>>> mingw uses symbol visibility "under the hood" for
>>> __declspec(dllimport/-export).
>>
>> I'm aware of this "fix".  I'm very reluctant to just do it because I
>> don't understand why it works or should work.
>
> It works because gcc and msvc have different symbol visibility rules.
> It seems to me that msvc works by "accident" or compiler "feature"
> right now. I've not taken the time to dig into the MS knowledge base
> to verify this, though.
>
>> So it's almost certain that if I just do this, It
>> will come back to torture me some time just after the next version is
>> released.
>
> Well, I discovered this behaviour when trying to fix the now famous
> #2114
>
> https://svn.boost.org/trac/boost/ticket/2114
>
> As soons as symbol visibility support is added to the serialization
> library, gcc will fail on _all_ platforms without those extra
> "#defines"

That is, there won't be a problem with the serialization library
until it changes to the new defines? That is as long as no one
uses autolink for that library?

> I'm quite short on time, but please find the whole patch adding
> symbols visibility support (and fixing #2114 for Boost.Serialization)
> attached.
> This already work for Boost.Test and Beman patched some more libs...

All this looks like a refinement of the auto-liink stuff which we've had
for MSVC and Borland for years.  So it's OK.  I would like to see
this stuff checked into the release branch before I make these changes
in the serialization library.

With the last change I made in the serialization library, the only missing
symbols are void_upcast and void_downcast.  the *.cpp files which
defiine these functions to indeed define BOOST_SERIALIZATION_SOURCE
so these symbols should be exported.  I'm trying go figure out why this is
not happening. Including define BOOST_SERIALIZATION_SOURCE in
a different file can't be the solution - the fact that it seems to work can 
only
be a hint as to what the problem is.  Still thanks for the insight.

Robert Ramey