# Extract linker args for dependencies
**URL:** https://discourse.cmake.org/t/extract-linker-args-for-dependencies/9702
**Category:** Code
**Created:** [December 22, 2023, 10:44pm UTC](https://discourse.cmake.org/t/extract-linker-args-for-dependencies/9702 "2023-12-22T22:44:48Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@tgross35](https://discourse.cmake.org/u/tgross35)
#### Post date: [December 22, 2023, 10:44pm UTC](https://discourse.cmake.org/t/extract-linker-args-for-dependencies/9702/1 "2023-12-22T22:44:48Z")
I have a setup where an external tool (cargo) produces a shared library, but it needs to be able to link dependencies generated by CMake. My current setup looks like this:
```cmake
add_custom_target(${target_name} ALL
COMMAND ${CMAKE_COMMAND}
${env_args}
${cargo_cmd}
--crate-type=cdylib
--
# This needs to contain `-l`/`-L` arguments
${rustc_extra_args}
WORKING_DIRECTORY ${rust_dir}
COMMENT "start cargo for ${target_name} with '${cargo_cmd}' dynamic"
VERBATIM
)
# `foo` and `bar` are created via `add_library` in some other file,
# also has some `target_link_libraryes` set
add_dependencies(${target_name} foo bar)
```
My problem is that the `add_custom_target` command needs to be passed `-l` and `-L` linker args to correctly link `libfoo` and `libbar`, including their transitive dependencies. This seems like a case for generator expressions, but I don’t see any on [this page](https://cmake.org/cmake/help/latest/manual/cmake-generator-expressions.7.html#link-context) that helps locate information about dependencies.
I also cannot query anything with `get_target_property` before the dependency is added.
Ideally I would have something simple that expands to `-Lnative=/build/foo-path -Lnative=/build/bar-path -lstatic=foo -lstatic=bar`, or just the full library paths to pass to the linker.
What is the best way to go about this? My current solution is to hand-write library output paths, but this isn’t very maintainable.
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [December 24, 2023, 1:30am UTC](https://discourse.cmake.org/t/extract-linker-args-for-dependencies/9702/2 "2023-12-24T01:30:28Z")
It’s a bit annoying but you can:
- write a target that links like the Rust target should
- set the [`_COMPILER_LAUNCHER` property](https://cmake.org/cmake/help/latest/prop_tgt/LANG_COMPILER_LAUNCHER.html) on that target and capture the relevant bits and write it to a file
- read that file and pass it to the `cargo` command as you see fit