# Handling of linker flags inconsistent

**URL:** https://discourse.cmake.org/t/handling-of-linker-flags-inconsistent/9827
**Category:** Development
**Created:** [January 11, 2024, 12:16pm UTC](https://discourse.cmake.org/t/handling-of-linker-flags-inconsistent/9827 "2024-01-11T12:16:51Z")
**Posts on this page:** 5
**Page:** 1

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### Author: ![Neumann-A](https://discourse.cmake.org/user_avatar/discourse.cmake.org/neumann-a/32/1647_2.png) [@Neumann-A](https://discourse.cmake.org/u/Neumann-A)
#### Post date: [January 11, 2024, 12:16pm UTC](https://discourse.cmake.org/t/handling-of-linker-flags-inconsistent/9827/1 "2024-01-11T12:16:51Z")

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While working on [https://gitlab.kitware.com/cmake/cmake/-/merge\_requests/9107](https://gitlab.kitware.com/cmake/cmake/-/merge_requests/9107) I noticed that linker flag handling is inconsistent.

**What exactly is inconsistent?**  
According to the docs variables like `CMAKE_SHARED_LINKER_FLAGS_<CONFIG>` are flags passed to the linker or flags used by the linker. This however is only true if the link rule is actually invoking the linker directly and not through the compiler frontend. As such the description is currently only true for Windows-MSVC where the link rules invoke link directly. Secondly, there are variables like `CMAKE_<LANG>_LINKER_WRAPPER_FLAG` which is used to tell cmake what to prepend to stuff added via target\_link\_options etc. This however leads to a design flag where the user actually needs to know the internal CMake rule to know if `CMAKE_SHARED_LINKER_FLAGS_<CONFIG>` should have `-Xlinker/-Wl,` or not. The problem is probably historic due to Makefiles typically invoking CC for linkage and using `LDFLAGS` directly, so it is always clear that `-Xlinker/-Wl,` is necessary (Ignoring manual written Makefile rules for MSVC etc.).

In my case wanting to using a clang(for CUDA/ASM)/clang-cl (for C/CXX) mixed toolchain it leads to the problem where one time the compiler is used for linkage and another time the linker ist used for linkage needing to define `CMAKE_SHARED_LINKER_FLAGS_<CONFIG>` theoretically on a language based level due to the above inconsistency with the link flags (probably could always add `-Xlinker` due to MSVC being nice about unknown flags but this would give a lot of warnings).

**Possible suggestions for a solution.**  
a) Prepend the wrapper flag to `CMAKE_SHARED_LINKER_FLAGS_<CONFIG>` if it isn’t there yet  
b) Use a response file for all given linker flags and always apply the wrapper flag. This would work `-Xlinker/-Wl,` and `/link`

So what would be the best solution for this problem going forward?

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### Author: ![ben.boeckel](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/b/ea5d25/32.png) [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [January 11, 2024, 2:04pm UTC](https://discourse.cmake.org/t/handling-of-linker-flags-inconsistent/9827/2 "2024-01-11T14:04:33Z")

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Cc: @brad.king

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### Author: ![brad.king](https://discourse.cmake.org/user_avatar/discourse.cmake.org/brad.king/32/11_2.png) [@brad.king](https://discourse.cmake.org/u/brad.king)
#### Post date: [January 11, 2024, 2:10pm UTC](https://discourse.cmake.org/t/handling-of-linker-flags-inconsistent/9827/3 "2024-01-11T14:10:50Z")

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> [@Neumann-A](#):
>
> According to the docs variables like `CMAKE_SHARED_LINKER_FLAGS_<CONFIG>` are flags passed to the linker or flags used by the linker.

These variables are meant to be command-line fragments of the final link line regardless of whether it is driven by a compiler driver or a direct linker invocation. Indeed the convention comes from the `$CC $LDFLAGS` days, and yes it requires whoever is setting the value to know how the link step is driven.

`target_link_options` is a more modern method of adding linker flags, and it provides the `LINKER:` prefix to map to any needed wrapper flag. Maybe we could consider resolving the `LINKER:` prefix inside the link flags variables too.

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### Author: ![Neumann-A](https://discourse.cmake.org/user_avatar/discourse.cmake.org/neumann-a/32/1647_2.png) [@Neumann-A](https://discourse.cmake.org/u/Neumann-A)
#### Post date: [January 11, 2024, 4:21pm UTC](https://discourse.cmake.org/t/handling-of-linker-flags-inconsistent/9827/4 "2024-01-11T16:21:15Z")

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> Maybe we could consider resolving the `LINKER:` prefix inside the link flags variables too.

That should make switching between different linker rules possible.

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### Author: ![brad.king](https://discourse.cmake.org/user_avatar/discourse.cmake.org/brad.king/32/11_2.png) [@brad.king](https://discourse.cmake.org/u/brad.king)
#### Post date: [January 22, 2024, 2:49pm UTC](https://discourse.cmake.org/t/handling-of-linker-flags-inconsistent/9827/5 "2024-01-22T14:49:20Z")

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I’ve opened [CMake Issue 25620](https://gitlab.kitware.com/cmake/cmake/-/issues/25620) for this.