[CMake] Newbie question: Static linking

[aaron.meadows at thomsonreuters.com]

>-----Original Message-----
>From: cmake-bounces at cmake.org [mailto:cmake-bounces at cmake.org] On
Behalf Of Michael Wild
>Sent: Monday, May 23, 2011 9:12 AM
>To: cmake at cmake.org
>Subject: Re: [CMake] Newbie question: Static linking
>
>On 05/23/2011 03:25 PM, Sanatan Rai wrote:
>> On 23 May 2011 13:38, Michael Wild <themiwi at gmail.com> wrote:
>>> On 05/23/2011 02:20 PM, Sanatan Rai wrote:
>>>> On 23 May 2011 12:54, Michael Jackson <mike.jackson at bluequartz.net>
wrote:
>>>>> You might want to take a look at the Factory design pattern.
>>>>>
>>>>
>>>> That's exactly what I use...
>>>>
>>>> --Sanatan
>>>
>>> Yes, but you are registering the concrete factories implicitly
instead
>>> of explicitly, which is causing you the trouble you experience.
>>>
>>> Better have your user provide a function registering his/her classes
>>> explicitly.
>> 
>> I guess this is getting to be off topic, but indeed the
>> anonymous namespace trick is supposed to do exactly that.
>> 
>> I am not trying to be difficult here---just that it is not clear to
me
>> that the solution to this problem is that straightforward.
>> 
>> When all the code files are linked in one monolithic bloc, everything
>> works correctly. It is when one starts dividing them into individual
>> libraries that this problem occurs. I haven't seen a solution to this
>> problem either in books or via google.
>> 
>> --Sanatan
>
>The problem is, that when you link a static library to another binary
>(be it shared library or executable) only the *required* symbols are
>used, all others get discarded. Since nothing in your code actually
>references those global instances in the anonymous namespace (the
linker
>doesn't care about that, BTW), they are ignored.
>
>Four solutions:
>
>1. Only do monolithic builds.
>2. Use shared libraries/DLLs
>3. Use --whole-archive or similar and hack your way through MSVC (I did
>it once. It was ugly. Very ugly. See
>https://github.com/themiwi/cppcheck/tree/227378f763d50b005b7dd2167e2cef
791054a30c.
>Especially lib/CMakeLists.txt and lib/generateStaticLinkFlags.cmake. I
>replaced it with an explicit registration scheme now...)
>4. Use an explicit registration scheme.
>
>For sanity's sake, go with 4.
>
>Michael

Couldn't you do:

5) Add references to the global instances inside something within the
same copilational unit which you know will be imported.  (Such as a
static reference to the global instance inside a function you know will
be called.)


Aaron

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