[CMake] Update builtin_cling=OFF configuration code
#18598
Conversation
In an attempt to further reduce build times, I attempted to build ROOT with `builtin_cling=OFF`, using a custom cling build that I install on my system. However, I ran into several errors with cling header files not being found, as well as linker errors. The simplest fix was to set the `GLOBAL` argument in `find_package(Cling)`, to make all the Cling targets available globally. Then, one also doesn't need all this code for the transient dependencies anymore (this is all handled correctly in the ClingConfig.cmake). The only caveat of this is that the `GLOBAL` argument is only available from CMake 3.24 onwards, so the configuration with `builtin_cling=OFF` will now error out if the CMake version is lower. That should be acceptable, since users that are adventurous enough to build ROOT like this probably also have a CMake version that is new enough (RHEL 9 has CMake version 3.26, and Ubuntu 24.04 has CMake version 3.28). Also, don't add any custom search paths to `find_package(Cling)` and `find_package(Clang)`, so that one is forced to use the `Clang_DIR` and `Cling_DIR` hints correctly.
Test Results 19 files 19 suites 4d 11h 27m 23s ⏱️ Results for commit 15f6743. ♻️ This comment has been updated with latest results. |
|
Can we improve the Cling cmake infrastructure when it is being discovered as a installed package. I do not think we ever invested time in this and it's probably worth it. |
|
Which part of the CMake do you mean exactly? With this PR, building ROOT with |
I meant to avoid needing |
|
@guitargeek I would appreciate if you could start adding me as reviewer for this kind of PRs....... |
In an attempt to further reduce build times, I attempted to build ROOT with
builtin_cling=OFF, using a custom cling build that I install on my system.However, I ran into several errors with cling header files not being found, as well as linker errors.
The simplest fix was to set the
GLOBALargument infind_package(Cling), to make all the Cling targets available globally. Then, one also doesn't need all this code for the transient dependencies anymore (this is all handled correctly in the ClingConfig.cmake).The only caveat of this is that the
GLOBALargument is only available from CMake 3.24 onwards, so the configuration withbuiltin_cling=OFFwill now error out if the CMake version is lower. That should be acceptable, since users that are adventurous enough to build ROOT like this probably also have a CMake version that is new enough (RHEL 9 has CMake version 3.26, and Ubuntu 24.04 has CMake version 3.28).Also, don't add any custom search paths to
find_package(Cling)andfind_package(Clang), so that one is forced to use theClang_DIRandCling_DIRhints correctly.