Linux 7.2 To Raise LLVM/Clang Compiler Requirement, Add Support For Distributed ThinLTO
Among the early pull requests sent in prior to today's Linux 7.1 release of new material aiming for Linux 7.2 were all the Kbuild updates.
For those compiling the Linux kernel using LLVM/Clang rather than GCC, one of the most notable Kbuild changes for Linux 7.2 is the raising of the build requirements. Up to now the Linux kernel could be built with Clang 15 and newer but that is being raised to Clang 17 and newer.
The requirement was raised to Clang 17 to better match the capabilities of the GCC compiler. LLVM/Clang 17 had addressed issues around its scope checker and a GCC 8.1+ incompatibility around variables marked with const being valid expressions for _static_assert and other macros. By raising the requirement to Clang 17, it's only a bump of one year in LLVM release cycles while easing those maintenance burdens.
The other notable Kbuild feature of Linux 7.2 is adding support for LLVM's Distributed ThinLTO "DTLTO" mode. The Distributed ThinLTO mode can lead to faster kernel builds than in-process ThinLTO. Since then LLVM DTLTO has continued improving for even better performance.
Linux 7.2 also is hardening Kconfig against potential null pointer dereferences, various typo fixes, a kconfig-sym-check target to look for dangling Kconfig symbol references, and more.
More details on these planned Kbuild upgrades for Linux 7.2 can be found via this pull request.
For those compiling the Linux kernel using LLVM/Clang rather than GCC, one of the most notable Kbuild changes for Linux 7.2 is the raising of the build requirements. Up to now the Linux kernel could be built with Clang 15 and newer but that is being raised to Clang 17 and newer.
The requirement was raised to Clang 17 to better match the capabilities of the GCC compiler. LLVM/Clang 17 had addressed issues around its scope checker and a GCC 8.1+ incompatibility around variables marked with const being valid expressions for _static_assert and other macros. By raising the requirement to Clang 17, it's only a bump of one year in LLVM release cycles while easing those maintenance burdens.
The other notable Kbuild feature of Linux 7.2 is adding support for LLVM's Distributed ThinLTO "DTLTO" mode. The Distributed ThinLTO mode can lead to faster kernel builds than in-process ThinLTO. Since then LLVM DTLTO has continued improving for even better performance.
Linux 7.2 also is hardening Kconfig against potential null pointer dereferences, various typo fixes, a kconfig-sym-check target to look for dangling Kconfig symbol references, and more.
More details on these planned Kbuild upgrades for Linux 7.2 can be found via this pull request.