[libcxx-commits] [PATCH] D113253: [runtimes] Fix building initial libunwind+libcxxabi+libcxx with compiler implied -lunwind

[Petr Hosek via Phabricator via libcxx-commits]

phosek added a comment.

In D113253#3137287 <https://reviews.llvm.org/D113253#3137287>, @mstorsjo wrote:

> I managed to reproduce the issue. @phosek, can you advise how to proceed from here?
>
> One part of the issue, is that setting `CMAKE_TRY_COMPILE_TARGET_TYPE` to `STATIC_LIBRARY` makes the initial detection step detect less things. In particular, if doing full link tests, cmake sets the `CMAKE_LIBRARY_ARCHITECTURE` variable to `x86_64-linux-gnu`. This seems to be vital for some parts of library detection. To show off the issue, one can execute this minimal standalone cmake snippet:
>
>   set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
>   project(Runtimes)
>   cmake_minimum_required(VERSION 3.10)
>   find_package(ZLIB)
>
> On Ubuntu, it fails to find zlib, but if the `set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)` line is uncommented, it finds it as expected.

I don't know the answer but I did some experiments.

This fails:

  set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
  project(Runtimes)
  set(CMAKE_TRY_COMPILE_TARGET_TYPE EXECUTABLE)
  cmake_minimum_required(VERSION 3.10)
  find_package(ZLIB)

This succeeds:

  project(Runtimes)
  cmake_minimum_required(VERSION 3.10)
  set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
  find_package(ZLIB)
  set(CMAKE_TRY_COMPILE_TARGET_TYPE EXECUTABLE)

So it seems like this is somehow related to the `project` configuration rather than the `find_package` implementation.

I'm looking into CMake implementation to see if I can figure what's going on.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D113253/new/

https://reviews.llvm.org/D113253