CODEWITHSUNDEEP
c++cmakeshared-librariesstatic-librariesobject-library
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Reputation: 45

Switching away from mixing static and shared libraries

I have a project where I mix between static and shared libs. The shared libs are delivered. Each shared lib is built with its correspondence static lib. A shared lib can depend on other shared libs as well. For example, I have: sharedA, sharedB, sharedC, staticA, staticB and staticC. SharedA is built with staticA inside and similar for other shared. Let's say sharedC, besides its dependency on staticC, also depends on sharedB.

For the static libraries, if they need dependency on another static one, I link against the one's correspondence shared lib. For example:

staticB depends on staticA. Hence, I link staticB against sharedA. The reason for this is to avoid size increase if statically declare staticB's dependency on staticA.

This system has been working. However, problem arises when I build the static libs with hidden visibility. The linker links with no error. But more than one symbols of a specific class might end up in the final symbol map. Therefore, the program can pick up the undesired one, which causes weird behaviour.

I have been reading about cmake object library, and probably switching the static libs to object libs could help in this case. I change the static libs to object, and get undefined symbol errors. I define dependency of an object lib on other, but still could not get rid of all the errors. My questions are:

  1. I am using target_link_libraries(obj2 PUBLIC obj) to declare dependency between 2 object libs. Can this be the reason for undefined symbol error I get? Because according to cmake documentation:

Object Libraries may "link" to other object libraries to get usage requirements, but since they do not have a link step nothing is done with their object files.

  1. Maybe I should switch to target_link_libraries(obj2 $<TARGET_OBJECTS:obj>) so obj2 is built with object files from obj.c? Another thing with this is: obj needs to be a library (created with add_library). In the function where I define all the links, obj is a variable and could not be put after $<TARGET_OBJECTS:. I have been looking around but not able to find anything. Is there a way I can put variable name after $<TARGET_OBJECTS:, or I have to refractor somehow to make this possible?

  2. Any other suggestion on how to do this would be helpful to me

Upvotes: 1

Views: 151

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