# Linker configuration in toolchain file for cross-compiling

**URL:** https://discourse.cmake.org/t/linker-configuration-in-toolchain-file-for-cross-compiling/14192
**Category:** Code
**Tags:** os:linux
**Created:** [June 3, 2025, 1:53pm UTC](https://discourse.cmake.org/t/linker-configuration-in-toolchain-file-for-cross-compiling/14192 "2025-06-03T13:53:03Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![nickvdbroeck](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/n/85f322/32.png) [@nickvdbroeck](https://discourse.cmake.org/u/nickvdbroeck)
#### Post date: [June 3, 2025, 1:53pm UTC](https://discourse.cmake.org/t/linker-configuration-in-toolchain-file-for-cross-compiling/14192/1 "2025-06-03T13:53:03Z")

</div>

I am trying to setup cross compilation using cmake.

I am working on windows 11. I am using WSL 2 with an Ubuntu-22.04 as host system to build on and my target system is an aarch64 embedded ARM processor running something like ubuntu. My current cmake support is for version 3.11 and upwards.

I have an SDK with the sysroot and all the build tools for the target system. This has been installed under `~/xos/env/sysroots/aarch64-linux/`. However that SDK has a gcc compiler (version 9.2.1) with an issue making it unable to find any std library.  
To solve this I also installed gcc for cross compiling directly from [https://developer.arm.com/-/media/Files/downloads/gnu-a/9.2-2019.12/binrel/gcc-arm-9.2-2019.12-x86\_64-aarch64-none-linux-gnu.tar.xz?revision=61c3be5d-5175-4db6-9030-b565aae9f766&rev=61c3be5d51754db69030b565aae9f766&hash=43A89163112C6A1E6DBBE3B14CC393143722BD0E](https://developer.arm.com/-/media/Files/downloads/gnu-a/9.2-2019.12/binrel/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu.tar.xz?revision=61c3be5d-5175-4db6-9030-b565aae9f766&rev=61c3be5d51754db69030b565aae9f766&hash=43A89163112C6A1E6DBBE3B14CC393143722BD0E)  
into the location `~/xos/gcc/`.

Based on this, I create a toolchain file like such:

```cmake
set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_PROCESSOR aarch64)
set(CMAKE_SYSROOT "${ROOT}sysroots/aarch64-linux/")

# Specify the cross compiler
set(CMAKE_C_COMPILER ${ROOT_GCC}aarch64-none-linux-gnu-gcc )
set(CMAKE_CXX_COMPILER ${ROOT_GCC}aarch64-none-linux-gnu-g++)

# indicate where the target environment libraries to include are located
set(CMAKE_FIND_ROOT_PATH ${CMAKE_SYSROOT }usr/lib)

# search executable programs in the host environment
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)

# search headers and libraries ONLY in the target environment
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

```

where `${ROOT}`, `${ROOT_GCC}` are defined in the CMakeUserPresets.json file to account for the user name of each developer. For example:

```json
{
  "version": 3,
  "configurePresets": [
    {
      "name": "MyRelease",
      "displayName": "release cross compile",
      "inherits": "base-release",
      "cacheVariables": {
        "ROOT_GCC": "~/xos/gcc/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/bin/",
        "ROOT": "~/xos/env/"
      }
    }
  ]
}

```

I am running this from Visual Studio 2022, but in cmake mode (so not through solution files).

The problem I have is that cmake gives me the following error:

```auto
1> Copying files to the remote machine.
..
1> Finished copying files (elapsed time 00h:00m:00s:392ms).
1> CMake generation started for configuration: 'MyRelease'.
1> Found cmake executable at /usr/bin/cmake.
1> /usr/bin/cmake -G "Ninja" -DCMAKE_BUILD_TYPE:STRING="Release" -DROOT_GCC="~/xos/gcc/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/bin/" -DROOT:STRING="~/xos/env/" -DCMAKE_INSTALL_PREFIX:PATH="~/.vs/<redacted>" -DCMAKE_TOOLCHAIN_FILE:FILEPATH="cmake/toolchains/WSL-ARM64.cmake" <redacted>/CMakeLists.txt;
1> [CMake] -- Setting up cross compilation toolchain
1> [CMake] -- The CXX compiler identification is GNU 9.2.1
1> [CMake] -- Detecting CXX compiler ABI info
1> [CMake] -- Detecting CXX compiler ABI info - failed
1> [CMake] -- Check for working CXX compiler: ~/xos/gcc/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/bin/aarch64-none-linux-gnu-g++
1> [CMake] -- Check for working CXX compiler: ~/xos/gcc/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/bin/aarch64-none-linux-gnu-g++ - broken
1> [CMake] CMake Error at /usr/share/cmake-3.22/Modules/CMakeTestCXXCompiler.cmake:62 (message):
1> [CMake] The C++ compiler
1> [CMake] 
1> [CMake] "~/xos/gcc/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/bin/aarch64-none-linux-gnu-g++"
1> [CMake] 
1> [CMake] is not able to compile a simple test program.
1> [CMake] 
1> [CMake] It fails with the following output:
1> [CMake] 
1> [CMake] Change Dir: <redacted>/out/build/MyRelease/CMakeFiles/CMakeTmp
1> [CMake]     
1> [CMake] Run Build Command(s):/usr/bin/ninja cmTC_7d34b && [1/2] Building CXX object CMakeFiles/cmTC_7d34b.dir/testCXXCompiler.cxx.o
1> [CMake] [2/2] Linking CXX executable cmTC_7d34b
1> [CMake] FAILED: cmTC_7d34b 
1> [CMake] : && ~/xos/gcc/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/bin/aarch64-none-linux-gnu-g++ --sysroot=sysroots/aarch64-linux/usr/lib CMakeFiles/cmTC_7d34b.dir/testCXXCompiler.cxx.o -o cmTC_7d34b && :
1> [CMake] ~/xos/gcc/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/bin/../lib/gcc/aarch64-none-linux-gnu/9.2.1/../../../../aarch64-none-linux-gnu/bin/ld: cannot find crt1.o: No such file or directory
1> [CMake] ~/xos/gcc/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/bin/../lib/gcc/aarch64-none-linux-gnu/9.2.1/../../../../aarch64-none-linux-gnu/bin/ld: cannot find crti.o: No such file or directory
1> [CMake] ~/xos/gcc/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/bin/../lib/gcc/aarch64-none-linux-gnu/9.2.1/../../../../aarch64-none-linux-gnu/bin/ld: cannot find -lm
1> [CMake] ~/xos/gcc/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/bin/../lib/gcc/aarch64-none-linux-gnu/9.2.1/../../../../aarch64-none-linux-gnu/bin/ld: cannot find -lc
1> [CMake] ~/xos/gcc/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/bin/../lib/gcc/aarch64-none-linux-gnu/9.2.1/../../../../aarch64-none-linux-gnu/bin/ld: cannot find crtn.o: No such file or directory
1> [CMake] collect2: error: ld returned 1 exit status
1> [CMake] ninja: build stopped: subcommand failed.
1> [CMake]     
1> [CMake] 
1> [CMake] CMake will not be able to correctly generate this project.
1> [CMake] Call Stack (most recent call first):
1> [CMake] CMakeLists.txt:21 (project)
1> [CMake] -- Configuring incomplete, errors occurred!
1> [CMake] See also "<redacted>/out/build/MyRelease/CMakeFiles/CMakeOutput.log".
1> [CMake] See also "<redacted>/out/build/MyRelease/CMakeFiles/CMakeError.log".
1> [CMake] 
1> cd "~/.vs/XManager/out/build/MyRelease";/usr/bin/cmake -G "Ninja" -DCMAKE_BUILD_TYPE:STRING="Release" -DROOT_GCC:STRING="~/xos/gcc/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/bin/" -DROOT:STRING="~/xos/env/" -DCMAKE_INSTALL_PREFIX:PATH="<redacted>/out/install/MyRelease" -DCMAKE_TOOLCHAIN_FILE:FILEPATH="cmake/toolchains/WSL-ARM64.cmake" <redacted> 2>&1; returned with exit code: 1

```

The error says that it cannot find `crt1.o` and such. Indeed, they are not in the gcc installation.  
Instead these file are located in the sysroot: `${CMAKE_SYSROOT}usr/lib`.

My question is how to make cmake handle this.

I learned from Googling the error that cmake is not calling the linker directly, but instead gcc is calling the linker and that I should somehow tell it to add this `${CMAKE_SYSROOT}usr/lib` to the search path for the linker. But how exactly to do this?  
I found the following variables, but none of them worked for me:

- `CMAKE_SYSROOT_LINK`
- `CMAKE_<LANG>_IMPLICIT_LINK_DIRECTORIES`

One thing I did noticed is that if I do not set the CMAKE\_SYSROOT variable, then everything compiles and links. But reading the ‘Professional cmake’ book, it strongly suggest to define this variable to indicate the cross compilation nature to CMake.

**Can anybody tell me which cmake variable I should set to indicate that it should include this `${CMAKE_SYSROOT}usr/lib` as search path towards the linker? Or how I should solve this issue?**

Thank you in advance.

> note: Whenever you see `~` or `<redacted>` the full path is actually present, but I removed it in this post for anonymity.