add_dependencies could not able to find system default libraries in 3.28.3

Usage
1

In the cmake 3.28.3, when I give library ( example here is libdl.so.2) , in the add_dependencies, its throwing an error: The dependency target “dl” of target “xxxx” does not exist.
add_dependencies(xxxx zzzz dl)
The dl library is there in the system: libc6:amd64: /usr/lib/x86_64-linux-gnu/libdl.so.2

How to solve this issue.

2

You need target_link_libraries() instead of add_dependencies(). The latter only takes cmake targets as arguments.

3

Thanks for your reply. There is already one target_link_libraries(xxxx glog gflags yyyy …) there, and when modified as per your advice,
target_link_libraries(xxxx glog gflags yyyy zzzz, dl)
its throwing the following error:
Target “zzzz” of type UTILITY may not be linked into another target. One
may link only to INTERFACE, OBJECT, STATIC or SHARED libraries, or to
executables with the ENABLE_EXPORTS property set.
I tried with separate target_link_libraries(xxxx zzzz, dl)
as well. Its throwing the same error
Any idea how to fix on this? This error is not coming when I use add_dependencies, but previous error is coming as I mentioned in my last mail.

Looking forward for your reply.

4

If I understand it right:

  • libdl.so.2 is a library on disk, external to your project.
  • zzzz is a custom target in your project (created by add_custom_target()).
  • You need your target xxxx to consume both.

add_dependencies() only accepts CMake targets as arguments, and introduces dependencies, but does not cause linking. target_link_libraries() accepts both targets and libraries, and causes them to be linked.

To link the library, use target_link_libraries(). To depend on a custom target (since these cannot be linked, they don’t correspond to anything linkable), use add_dependencies(). Put together:

add_dependencies(xxxx dl)
target_link_libraries(xxxx zzzz)
5

add_dependencies(xxxx dl) does not work on cmake 3.28.3 as I am seeing the same error. Probably this could not find the libdl.so file.
The dependency target “dl” of target “xxxx” does not exist.
I added the following changes and its not throwing any error. Are these changes are fine or do we have any alternative way to fix this issue.
find_library(DL libdl.so)
add_custom_target(custom_dl ${DL})
add_dependencies(xxxx custom_dl)

here add_custom_target is compulsory or any other way we can do it?

Regards,

6

I think you confused zzzz and dl in your code example. It should be:

add_dependencies(xxxx zzzz)
target_link_libraries(xxxx dl)

[/quote]

if zzzz is a custom target and libdl.so is the library file or a link to it (note: without .2 at the end)

7

This does nothing useful.

8

Thank you for an update. This is what I understood from your explanation. All installed libraries in the OS (like dl, gflags,… ) has to included using the target_link_libraries. And all the cmake generated targets need to be added using add_dependencies.

There is one more Question. If my target depends on the header file (x.h), how can I add that.
add_executible(xxxx < set of source files >)
target_link_libraries(xxxx yyyy zzzz)
add_dependencies(xxxx x.h)

This code snippet throwing the same error: The dependency target “x.h” of target “xxxx” does not
exist.
Note: this was working fine with 3.16.3 and seeing issues with 3.28.

9

Manually adding dependencies is rather the exception, e.g. when needing a specific build order.

It seems, you are unfamiliar with CMake, did you look at the tutorials?

11

Header files are source files. There are exceptions for generated headers in other directories.