gcc - cmake library linking order -

i have following libraries lib_a, lib_b, lib_c, lib_d. doing in cmake files (order important):

1. add_library(lib_a)
2. add_library(lib_b)
3. add_library(lib_c)
4. add_library(lib_d)
5. target_link_libraries(lib_b lib_c)
6. target_link_libraries(lib_a lib_b)
7. add_executable(exec)
8. target_link_libraries(exec lib_a)
9. target_link_libraries(exec lib_d)

this results in following linker command.

linker -llib_a -llib_d -llib_b -llib_c

q1. why lib_b , lib_c after lib_d?

q2. when change cmake little bit , this:

8_ target_link_libraries(lib_a lib_d) 9_ target_link_libraries(exec lib_a)

then linking order linker -llib_a -llib_b -llib_c -llib_d here, lib_b , lib_c before lib_d. means target_link_libraries works differently executable targets , library targets. right?

the problem here lib_b , lib_c depend on lib_d don't want make target_link_libraries(lib_b lib_d) , target_link_libraries(lib_c lib_d), because have more of such cases , have manually each library. of course doing in q2 solves problem q3 - order guaranteed somehow cmake or fortuity?

thank you

just link lib_b , lib_c libd, it's worth effort (i can tell experience), otherwise have big troubles, example if try install program. lib_c , lib_d should have symbols solved when finished creating library files, before linking them other library.

by way, can compact target_link_libraries in 1 line per target, like:

target_link_libraries(exec lib_a lib_d) 

and, if exec doesn't depend directly on lib_d, can avoid linking if have correctly linked lib_a lib_d.

anyway, regarding q1: if order guaranteed cmake, not guaranteed way your linker treat it, going suffer pain if rely on that