Is target specific stuff transitive to dependencies?

Usage
8

It makes perfectly sense (I did use makefile a lot some time ago), but I bet that in that case commonLib is not really a “library” since it shall be recompiled for different app. What you describe is a way to bring in a new commonLib-A into A by specifying a set of source file that need to be recompiled for A.

So you need to create your interface library, with appropriate associated source files in it:

add_library(common INTERFACE)
target_include_directories(common INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})
target_sources(common INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/common.cpp)

then:

add_executable(A-app a.cpp)
target_link_libraries(A-app common)
target_compile_definitions(A-app PRIVATE withA)

add_executable(B-app b.cpp)
target_link_libraries(B-app common)
target_compile_definitions(B-app PRIVATE withB)

and you’ll get what you want (I guess).
see:

$ ninja -v 
[1/6 (4) - 0.155] /usr/bin/c++  -DwithB -I../  -MD -MT CMakeFiles/B-app.dir/common.cpp.o -MF CMakeFiles/B-app.dir/common.cpp.o.d -o CMakeFiles/B-app.dir/common.cpp.o -c ../common.cpp
[2/6 (3) - 0.220] /usr/bin/c++  -DwithA -I../  -MD -MT CMakeFiles/A-app.dir/common.cpp.o -MF CMakeFiles/A-app.dir/common.cpp.o.d -o CMakeFiles/A-app.dir/common.cpp.o -c ../common.cpp
[3/6 (2) - 0.240] /usr/bin/c++  -DwithB -I../  -MD -MT CMakeFiles/B-app.dir/b.cpp.o -MF CMakeFiles/B-app.dir/b.cpp.o.d -o CMakeFiles/B-app.dir/b.cpp.o -c ../b.cpp
[4/6 (2) - 0.285] /usr/bin/c++  -DwithA -I../  -MD -MT CMakeFiles/A-app.dir/a.cpp.o -MF CMakeFiles/A-app.dir/a.cpp.o.d -o CMakeFiles/A-app.dir/a.cpp.o -c ../a.cpp
[5/6 (2) - 0.309] : && /usr/bin/c++     CMakeFiles/B-app.dir/b.cpp.o CMakeFiles/B-app.dir/common.cpp.o  -o B-app   && :
[6/6 (1) - 0.357] : && /usr/bin/c++     CMakeFiles/A-app.dir/a.cpp.o CMakeFiles/A-app.dir/common.cpp.o  -o A-app   && :

Here comes the archive of this:
target_specific_define.zip (1.7 KB)

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