[CMake] link static libraries to a share library

[Michael Hertling]

On 04/07/2011 07:37 PM, Jiang Xu wrote:
> Hi All,
> 
> I am new to cmake, but I really like it after looking into it.
> I am in the process to make some changes to our current make file system.
> I wonder how can I archieve the following goal using cmake:
> 
> 1.  The root directory is features/
> 2.  Under root directory, there is a set of subdirectories as: feature_1/, feature_2/, ... feature_n/
> 3.  Under each subdirectory, there is a CMakeList.txt to compile a static library for each feature. For example, in CMakeList.txt under feature_1 directory, it has a line to create static library target: add_library(feature_1, STATIC, ${FEATURE_1_SRCS})
> 4.  Under root directory, there is no source code, all it does is based on user input (command line) to go into different sub-directories to build each static libraries and try to link all of them into a shared library.
> 
> It looks like add_library command must have any source code files in it.  So I don't know how to add a shared library target and all it does is to link different static libraries, there is no source file.  Can someone please help me?
> 
> Thanks in advance.
> 
> John

This is not possible with CMake, cf. [1]. Instead, you'll have either to

- build one shared library in each feature_* directory to link against,
  e.g. ADD_LIBRARY(feature_1 SHARED feature_1.c ...) in feature_1, or
- build one shared library in the root directory with all the sources
  from the feature_* directories, e.g. ADD_LIBRARY(features SHARED
  feature_1/feature_1.c feature_2/feature_2.c ...) in features.

Besides, object files for static libraries and object files for shared
libraries are usually compiled with different flags, in particular with
regard to -fPIC, so they might not be interchangeable without further ado.

'hope that helps.

Regards,

Michael

> [1] http://www.cmake.org/Wiki/CMake_FAQ#Does_CMake_support_.22convenience.22_libraries.3F