# Can't add linker options no matter what
**URL:** https://discourse.cmake.org/t/cant-add-linker-options-no-matter-what/12941
**Category:** Usage
**Created:** [November 11, 2024, 4:03pm UTC](https://discourse.cmake.org/t/cant-add-linker-options-no-matter-what/12941 "2024-11-11T16:03:49Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@nolan](https://discourse.cmake.org/u/nolan)
#### Post date: [November 11, 2024, 4:03pm UTC](https://discourse.cmake.org/t/cant-add-linker-options-no-matter-what/12941/1 "2024-11-11T16:03:49Z")
Hey folks, not sure what I’m doing wrong here. I’m attempting to build a CMake project, github .com/duckdb/duckdb\_spatial for Android and am failing to set linker options for a dependency.
The project uses a Makefile to kick off its build. So in order to do the simplest thing that could possibly work, I add a simple build target pointing to the hard-coded NDK rules path on my system:
```auto
android_release:
mkdir -p build/release/android && \
cmake $(GENERATOR) $(BUILD_FLAGS) $(CLIENT_FLAGS) -DCMAKE_BUILD_TYPE=Release -S ./duckdb/ -DCMAKE_TOOLCHAIN_FILE=/home/nolan/android/android-ndk-r27c/build/cmake/android.toolchain.cmake -DANDROID_ABI=arm64-v8a -B build/release/android && \
cmake --build build/release/android --config Release
```
Running that gives me this:
```auto
[40%] Linking C shared library libz.so
ld.lld: error: version script assignment of 'local' to symbol 'gz_intmax' failed: symbol not defined
clang: error: linker command failed with exit code 1 (use -v to see invocation)
```
The solution (github .com/llvm/llvm-project/issues/75056, edited because I exceeded the number of links I can post) seems to involve adding `-Wl,--undefined-version` to my linker flags and _nothing_ I do seems to achieve that. Things I’ve tried:
- `LDFLAGS="-Wl,--undefined-version" make android_release`
- Adding `-DLDFLAGS=-Wl,--undefined-version` or `-DCMAKE_LDFLAGS=-Wl,--undefined-version` to the new android\_release target defined above
- Adding the above `-D` flags [here](https://github.com/duckdb/duckdb_spatial/blob/7ea79b614755d2bdee4be468691e4e17b39b8dbc/deps/CMakeLists.txt#L51)
- Adding `add_link_options(-Wl,--undefined-version)` [here](https://github.com/duckdb/duckdb_spatial/blob/7ea79b614755d2bdee4be468691e4e17b39b8dbc/deps/CMakeLists.txt#L14)
Nothing makes a difference and this compilation error persists. zlib is added as an external project vendored in the source tree, and appears to be built via cmake as well. How do I add a linker option that isn’t another library to the zlib project? Bonus points if I can scope the option specifically to Android builds.
Thanks.
---
### Author:  [@nolan](https://discourse.cmake.org/u/nolan)
#### Post date: [November 19, 2024, 5:57pm UTC](https://discourse.cmake.org/t/cant-add-linker-options-no-matter-what/12941/2 "2024-11-19T17:57:23Z")
Wanted to bump this since I’m periodically returning to this and smashing my head against it without a lot of success. My latest attempt:
```auto
# ZLIB
ExternalProject_Add(
ZLIB
URL ${CMAKE_CURRENT_SOURCE_DIR}/vendor/zlib1213.zip
CONFIGURE_HANDLED_BY_BUILD TRUE
CMAKE_ARGS
-DCMAKE_INSTALL_PREFIX:PATH=${LOCAL_INSTALL_DIR}
-DCMAKE_PREFIX_PATH=${LOCAL_INSTALL_DIR}
-DCMAKE_MODULE_PATH=${LOCAL_INSTALL_DIR}/lib/cmake
-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
-DCMAKE_OSX_ARCHITECTURES=${CMAKE_OSX_ARCHITECTURES_PACKED}
-DCMAKE_POSITION_INDEPENDENT_CODE=ON
-DBUILD_SHARED_LIBS=OFF
${CMAKE_FLAGS_POINTER_SIZE}
# vcpkg options
-DVCPKG_MANIFEST_DIR='${VCPKG_MANIFEST_DIR}'
-DVCPKG_INSTALLED_DIR='${VCPKG_INSTALLED_DIR}'
-DCMAKE_TOOLCHAIN_FILE='${CMAKE_TOOLCHAIN_FILE}'
-DVCPKG_TARGET_TRIPLET='${VCPKG_TARGET_TRIPLET}'
)
# I added this:
target_link_options(zlib, -Wl,--undefined-version)
```
This gives:
```auto
-- Detecting CXX compile features - done
CMake Error at CMakeLists.txt:60 (target_link_options):
Cannot specify link options for target "zlib," which is not built by this
project.
```
Duh it isn’t built by this project, but it seems like a build system aught to allow me to add target-specific link options to a subproject if I happen to know that a given toolchain requires them. I don’t know why this is so difficult and I’ve been pouring through docs/SO posts/GitHub issues without a lot of success. Interestingly, this post now shows up in my Google results for this problem.
Thanks so much for any help. Apologies for the spammy-looking attempts at links in the first post.
---
### Author:  [@fenrir](https://discourse.cmake.org/u/fenrir)
#### Post date: [November 20, 2024, 7:54am UTC](https://discourse.cmake.org/t/cant-add-linker-options-no-matter-what/12941/3 "2024-11-20T07:54:33Z")
I don’t have an answer, but I can tell you right away, that the ExternalProject just kicks off a separate build. That means you will not have “zlib” available to you right away, and at the moment you’ll have it (for example found by `find_package`), it will already be built, thus not accepting any modifications to the build process.
Note that `FetchContent` does not have this limitation.