I have a few small components that I am building as shared libraries for my main application. Lets use an example of liba
and libb
. Each is built within their own subdirectory as follows:
add_library(liba SHARED a.cpp)
Then, in the root project folder, I need to link my main application to both.
include_directories(a) include_directories(b) add_executable(dummy dummy.cpp) target_link_libraries(dummy a b)
CMake runs fine with this, and my application compiles but fails to link. The problem is that b references a. If I supply the order of the libraries while linking as
target_link_libraries(dummy b a)
The program compiles and links just fine
When this sort of system starts involving more complex inter dependency of the libraries, it starts to be impossible even if the dependencies are acyclic. How do I manage the linking step here? Is there a trick to ordering libraries for linking in CMake?
@FreelanceConsultant - no. The order of target creation does not affect the order of command execution. Only dependency order matters.
Link order certainly does matter, at least on some platforms. I have seen crashes for applications linked with libraries in wrong order (where wrong means A linked before B but B depends on A).
You can specify the relationship between a
and b
by adding
target_link_libraries(b a)
From the docs:
Library dependencies are transitive by default. When this target is linked into another target then the libraries linked to this target will appear on the link line for the other target too.
So, if you specify a
as a dependency of b
in this way, you don't even need to explicitly list a
in any target which depends on b
, i.e. your other command can be just:
target_link_libraries(dummy b)
although it wouldn't do any harm to list a
as well.
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