cmake, ci: updates for recent nixpkgs#238
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Without this change, building with -DMP_ENABLE_IWYU=ON and newer versions of nixpkgs (after 2025-11-12) fails with mysterious errors that look like: make[2]: *** [CMakeFiles/mputil.dir/build.make:79: CMakeFiles/mputil.dir/src/mp/util.cpp.o] Error 1 with no other error messages. The are no messages because cmake -E __run_co_compile hides the output from IWYU and does not display anything itself. The actual problem is missing include directories on the compiler command line, and the fix here is to extend a workaround previously added for clang-tidy to be used for IWYU as well. Breakage seems to have been caused by NixOS/nixpkgs@76a8ffa from NixOS/nixpkgs#445095, which I found by bisecting with --first-parent to a change between the following merge commit: https://github.com/NixOS/nixpkgs/commits/de21549a840be528ef4763dd7dca2006caf9c11f (bad) https://github.com/NixOS/nixpkgs/commits/c4d1151093af5d483d1900d9214a65e68bc21560 (good) If you check out the bad commit above (or any later commit) and revert NixOS/nixpkgs@76a8ffa the problem disappears. I suspect the problem happens because cmake is not handling -cxx-isystem properly, but did not debug further. The later change NixOS/nixpkgs#462747 which followed up on NixOS/nixpkgs#445095 did not seem to have any effect on this issue in my testing.
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CMake 4.0 dropped support for older policies, so versions of Cap'n Proto <= v1.1.0 (before capnproto/capnproto#2272) require an additional option to build with CMake 4.0. Without this change, there are errors like: > CMake Error at CMakeLists.txt:1 (cmake_minimum_required): > Compatibility with CMake < 3.5 has been removed from CMake. > > Update the VERSION argument <min> value. Or, use the <min>...<max> syntax > to tell CMake that the project requires at least <min> but has been updated > to work with policies introduced by <max> or earlier. > > Or, add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to try configuring anyway. This change fixes the problem by specifying -DCMAKE_POLICY_VERSION_MINIMUM=3.5 when needed.
ryanofsky
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Updated b66a6d3 -> db7acb3 ( |
sedited
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Feb 2, 2026
hebasto
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Feb 2, 2026
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This PR fixes two problems that happen with recent nixpkgs. The first commit works around compilation errors that happen when IWYU is enabled with (
-DMP_ENABLE_IWYU=ON) that were caused by NixOS/nixpkgs#445095. The second commit fixes problems building old versions of Cap'n Proto with CMake 4.0 in shell.nix.Neither problem has showed up so far running in github actions, only running locally with unstable nixpkgs. More details about the problems and fixes are in the commit messages.