Re: [boost] [filesystem][iostreams][program_options] linker issues on msvc

Subject: Re: [boost] [filesystem][iostreams][program_options] linker issues on msvc
From: Alexander Arhipenko (arhipjan_at_[hidden])
Date: 2009-11-21 07:10:45

On Sat, Nov 21, 2009 at 11:20 AM, Vladimir Prus
<vladimir_at_[hidden]> wrote:
> Alexander Arhipenko wrote:
>
>>
>>
>> Index: libs/filesystem/build/Jamfile.v2
>> ===================================================================
>> --- libs/filesystem/build/Jamfile.v2  (revision 57802)
>> +++ libs/filesystem/build/Jamfile.v2  (working copy)
>> @@ -11,6 +11,7 @@
>>  project boost/filesystem
>>      : source-location ../src
>>      : usage-requirements # pass these requirement to dependents (i.e. users)
>> +      <library>/boost/system
>>        <link>shared:<define>BOOST_FILESYSTEM_DYN_LINK=1
>>        <link>static:<define>BOOST_FILESYSTEM_STATIC_LINK=1
>>      ;
>
> Alexander,
> do you actually need the above patch? Because boost.filesystem has boost.system
> in sources, you should not need to add it to usage requirements.
>
> Could you clarify?
>
> I have checked in two other changes in your patch. Thanks!
>
> - Volodya
>

Hi Volodya,

I thinks the filesystem's patch is required and will try to clarify why.

Here is minimal example that reproduces the issue:
#Jamfile.v2:

exe foo : main.cpp /boost/filesystem ;

//main.cpp:

#include <boost/filesystem.hpp>

int main(int argc, char* argv)
{
   return 0;
}

In this case following error appears:

main.obj : error LNK2019: unresolved external symbol
"__declspec(dllimport) class boost::system::error_category const &
__cdecl boost::system::get_system_category(void)"
(__imp_?get_system_category_at_system@boost@@YAABVerror_category_at_12@XZ)
referenced in function "void __cdecl boost::system::`dynamic
initializer for 'system_category''(void)"
(??__Esystem_category_at_system@boost@@YAXXZ)

The reason is:
#include <boost/filesystem.hpp> --> includes <boost/path.hpp> -->
includes <boost/system/system_error.hpp> --> includes
<boost/system/error_code.hpp>

File boost/system/error_code.hpp has following declarations:

BOOST_SYSTEM_DECL const error_category &  get_system_category();
BOOST_SYSTEM_DECL const error_category &  get_generic_category();

So, when the header above is included in main.cpp, BOOST_SYSTEM_DECL unrolls to:
__declspec(dllimport).
And this causes the linker error.

As a result, library that links boost::filesystem should link boost::system.

Regards