Hi. First off, I discovered this bug when I build clang 11.0 with CMake 3.19. Here is the relevant part from [llvmorg-11.0.0/clang/CMakeLists.txt](https://github.com/llvm/llvm-project/blob/llvmorg-11.0.0/clang/CMakeLists.txt): ```cmake find_package(LLVM REQUIRED HINTS "${LLVM_CMAKE_PATH}") ``` In fact, CMake 3.18 was using `/lib/clang/llvm/LLVMConfig.cmake`, which is what I wanted, but realized that CMake 3.19 was using `/usr/lib/clang/llvm/LLVMConfig.cmake` instead (NOTE: `LLVM_CMAKE_PATH` is empty). --- The behavior of `find_package` seems to have changed between CMake 3.18 and 3.19. In fact, when `find_package(FOO)` will search for `/usr/lib/cmake/foo/{FOOConfig,foo-config}.cmake` but not for `/lib/cmake/foo/{FOOConfig,foo-config}.cmake` in the new 3.19-rc1. Is this expected? Here is a minimal reproducible example. I used Sourcehut Builds with Alpine 3.12 to build CMake 3.18 and CMake 3.19, both with `/usr` and `/` as prefix (as I found out, the prefix does not alter the behavior). I also executed the compiled CMake on a dummy project. ```cmake cmake_minimum_required(VERSION 3.18) project(hello) find_package(FOO) add_executable(hello main.c) ``` ```c #include <stdio.h> int main(void) { puts("hello"); } ``` Here is the output with `-D CMAKE_FIND_DEBUG_MODE=ON`: CMake 3.18.4 with / as prefix: https://builds.sr.ht/~iemaghni/job/321608#task-build-2329 CMake 3.19.0-rc1 with / as prefix: https://builds.sr.ht/~iemaghni/job/321587#task-build-2329 CMake 3.18.4 with /usr as prefix: https://builds.sr.ht/~iemaghni/job/321639#task-build-2248 CMake 3.19.0-rc1 with /usr as prefix: https://builds.sr.ht/~iemaghni/job/321621#task-build-2249 Here is the essential output for CMake 3.18.4: ``` find_package considered the following locations for the Config module: /FOOConfig.cmake /foo-config.cmake /lib/cmake/foo/FOOConfig.cmake /lib/cmake/foo/foo-config.cmake /usr/FOOConfig.cmake /usr/foo-config.cmake /usr/lib/cmake/foo/FOOConfig.cmake /usr/lib/cmake/foo/foo-config.cmake /usr/local/FOOConfig.cmake /usr/local/foo-config.cmake /opt/FOOConfig.cmake /opt/foo-config.cmake The file was not found. ``` and for CMake 3.19.0-rc1: ``` find_package considered the following locations for the Config module: /FOOConfig.cmake /foo-config.cmake /usr/FOOConfig.cmake /usr/foo-config.cmake /usr/lib/cmake/foo/FOOConfig.cmake /usr/lib/cmake/foo/foo-config.cmake /usr/local/FOOConfig.cmake /usr/local/foo-config.cmake /opt/FOOConfig.cmake /opt/foo-config.cmake The file was not found. ``` As you see, these two lines are missing from the new version: ``` /lib/cmake/foo/FOOConfig.cmake /lib/cmake/foo/foo-config.cmake ``` Here is the template that I used. Only `CMAKE_VER`, `CMAKE_CHKSUM` and `--prefix=` change between the builds: ```yaml image: alpine/3.12 packages: - pigz - linux-headers environment: CMAKE_VER: 3.18.4 CMAKE_CHKSUM: 597c61358e6a92ecbfad42a9b5321ddd801fc7e7eca08441307c9138382d4f77 tasks: - build: | >"cmake-${CMAKE_VER}.tar.gz" curl "https://cmake.org/files/v${CMAKE_VER%.*}/cmake-${CMAKE_VER}.tar.gz" set -- $(sha256sum "cmake-${CMAKE_VER}.tar.gz") test "$1" = "$CMAKE_CHKSUM" <"cmake-${CMAKE_VER}.tar.gz" pigz -d | tar -x -f - MAKEFLAGS="-j $(nproc)" export MAKEFLAGS mkdir -p cmake-build test test-build cd cmake-build "../cmake-${CMAKE_VER}/bootstrap" --prefix=/ -- -D CMAKE_USE_OPENSSL=OFF >'/dev/null' make sudo make install cd ../test >'CMakeLists.txt' printf 'cmake_minimum_required(VERSION 3.18)\nproject(hello)\nfind_package(FOO)\nadd_executable(hello main.c)\n' >'main.c' printf '#include <stdio.h>\nint main(void) { puts("hello"); }\n' cd ../test-build sudo mkdir -p /usr/lib/cmake/foo /lib/cmake/foo cmake -D CMAKE_FIND_DEBUG_MODE=ON ../test make ./hello ```