doc: Add note for building on macOS (Intel) with CMake ≥ 4.0 #32289

1. 
   hebasto commented at 4:23 pm on April 16, 2025: member

   Due to changes in CMake 4.0, building on macOS (Intel) no longer silences warnings from Homebrew-installed packages, such as boost or libevent.

   This PR adds a note to the macOS Build Guide to work around this issue.

   For technical background, see the following discussions:

   • https://gitlab.kitware.com/cmake/cmake/-/issues/19180
   • https://gitlab.kitware.com/cmake/cmake/-/merge_requests/10636
2. doc: Add note for building on macOS (Intel) with CMake ≥ 4.0

   See: https://gitlab.kitware.com/cmake/cmake/-/merge_requests/10636.

   05b77b55cc
3. hebasto added the label Docs on Apr 16, 2025
4. hebasto added the label macOS on Apr 16, 2025
5. 
   DrahtBot commented at 4:23 pm on April 16, 2025: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/32289.

   Reviews

   See the guideline for information on the review process. A summary of reviews will appear here.

6. in doc/build-osx.md:148 in 05b77b55cc

   144@@ -145,6 +145,8 @@ It is required that you have `python` and `zip` installed.
   145 
   146 ### 1. Configuration
   147 
   148+Note: On macOS (x86_64), users with CMake ≥ 4.0 and Homebrew installed in `/usr/local` should pass `-DCMAKE_OSX_SYSROOT=macosx` or `export SDKROOT=macosx` when not building with Homebrew-provided tools.
   

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   fanquake commented at 9:21 am on April 17, 2025:

   This says it applies to users with Homebrew installed, when not building with homebrew-provided tools? What are the “tools” here? This seems vauge, and as a user reading this I probably wouldn’t know if it applies to me.

   ---

   

   hebasto commented at 9:50 am on April 17, 2025:

   This says it applies to users with Homebrew installed, when not building with homebrew-provided tools? What are the “tools” here?

   For example, LLVM toolchain.

7. 
   fanquake commented at 9:22 am on April 17, 2025: member

   Not sure. I see this is just copied from the CMake release notes, but it doesn’t really explain anything, and it’s not clear what warnings that were being supressed no-longer are. Also seems like the warnings are a sideeffect of some other issues, that should probably be fixed properly, in some way.
8. 
   hebasto commented at 9:48 am on April 17, 2025: member

   … that should probably be fixed properly, in some way.

   I haven’t found a way to do it that covers all use cases, is user-friendly, and doesn’t introduce excessive complexity.

9. 
   janb84 commented at 8:06 am on April 18, 2025: contributor

   … that should probably be fixed properly, in some way.

   I haven’t found a way to do it that covers all use cases, is user-friendly, and doesn’t introduce excessive complexity.

   Maybe one “solution” is not to lean only on homebrew but offer also an alternative package manager e.g. nix ? (nix is still on cmake 3.31 so not sure what will happen when they are on 4.0 )

Contributors
hebasto DrahtBot fanquake janb84

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