OpenAFS Master Repository branch, master, updated. openafs-devel-1_9_2-417-gaacf65b

[Gerrit Code Review]

The following commit has been merged in the master branch:
commit aacf65b02b38a6a19d74a20147963980d6831e87
Author: Cheyenne Wills <cwills@sinenomine.net>
Date:   Tue Dec 16 18:36:27 2025 -0700

    cf: Linux kernel compiler version checks
    
    When building the Linux kernel module, the compiler version should match
    the compiler version that was used to build the Linux kernel itself.
    Using a different compiler or a significantly different version may lead
    to unexpected results. While modern Linux build systems do perform a
    compiler version check, the output is often filtered out or suppressed
    by the OpenAFS configure and kernel module build steps, hiding potential
    mismatches from the user. Furthermore, an incompatible compiler may
    cause silent failures in the configure tests used to determine kernel
    features.
    
    To avoid introducing complex checks within the existing kernel feature
    tests, a new configure check is added that runs before any other kernel
    module build tests. This new check first extracts the compiler version
    used to build the kernel by checking .config or falling back to header
    files for older kernels. It then determines the compiler version that
    will be used to build the module by invoking the kbuild process.
    Finally, it compares the versions, if there are differences it will
    log the differences, and issue warnings if the compiler type (e.g. gcc
    vs clang) or the major version (e.g. gcc-13 vs gcc-15) of the compiler
    are different.  If the difference is just the minor version (e.g.
    gcc-13.2 vs gcc-13.5), the log will note that the compilers are
    different versions, but no warnings will be logged.
    
    The Linux kernel kbuild process may also generate warnings or errors;
    if these are detected, the stderr from the kbuild will be added to the
    config.log.  Some of the information produced by the kbuild process
    may duplicate the information generated by the configure check.  The
    Linux kernel kbuild process may also report a difference if the exact
    name of the compiler doesn't match, even though the compiler types and
    compiler versions are the same.
    
    The check is designed to be informational; it issues informational and
    warning messages but does not halt the configure process. These messages
    can aid in problem determination if the kernel module build process
    fails.
    
    Add a new macro LINUX_KBUILD_COMPILER_CHECK and helper routines to a new
    file, src/cf/linux-kernel-compiler.m4. The call to this new check is
    inserted before the existing kernel build checks. Update the configure
    summary to display both the kernel's compiler version and the module
    build compiler version.
    
    Notes:
    Current Linux kernels place the compiler version within the .config
    file (Linux >= 5.8), while older versions placed the compiler version
    within a header file (whose location was changed at least once
    between 2.6.18 and 5.8).
    
    Determining the compiler version that will be used for building the
    kernel module requires running the compiler within the kernel kbuild
    process.  Use the gnu make $(shell ...) feature to run the compiler and
    the $(info ...) feature to display the result (these features are also
    used by the Linux kbuild processes).
    
    Example logging output:
    
    * configure console with the same compiler
     ...
      checking whether C compiler accepts -pipe... yes
      checking kernel compiler versions... same
      checking how to set cflags for linux kbuild... ccflags-y
     ...
      Linux kernel module
      ...
        kernel compiled with   : gcc (Gentoo 14.3.1_p20250801 p4) 14.3.1 20250801
        module C compiler      : gcc (Gentoo 14.3.1_p20250801 p4) 14.3.1 20250801
      ..
    
    * config.log with the same compiler:
     ...
      configure:20227: checking kernel compiler versions
      configure:20356: result: same
     ...
    
    * configure console where the compiler has a major version difference:
    
     ...
      checking whether C compiler accepts -pipe... yes
      checking kernel compiler versions... configure: kernel compiler versions are different, see config.log
      configure: WARNING: Compiler major versions differ, kernel module may be unusable
      different
      checking how to set cflags for linux kbuild... ccflags-y
     ...
      Linux kernel module
      ...
        kernel compiled with   : gcc (Gentoo 14.3.1_p20250801 p4) 14.3.1 20250801
        module C compiler      : gcc-15 (Gentoo 15.2.1_p20251122 p4) 15.2.1 20251122
      ...
    * config.log where the compiler has a major version difference
      ...
      configure:20227: checking kernel compiler versions
      warning: the compiler differs from the one used to build the kernel
        The kernel was built by: gcc (Gentoo 14.3.1_p20250801 p4) 14.3.1 20250801
        You are using:           gcc-15 (Gentoo 15.2.1_p20251122 p4) 15.2.1 20251122
      configure:20359: kernel compiler versions are different, see config.log
      kernel compiled with : gcc (Gentoo 14.3.1_p20250801 p4) 14.3.1 20250801
      kmod compiling with  : gcc-15 (Gentoo 15.2.1_p20251122 p4) 15.2.1 20251122
      configure:20370: WARNING: Compiler major versions differ, kernel module may be unusable
      configure:20373: result: different
    
    Change-Id: I8b37ffde14579726ab4e3443b54c84f9edf7f9a1
    Reviewed-on: https://gerrit.openafs.org/16655
    Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
    Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
    Tested-by: BuildBot <buildbot@rampaginggeek.com>
    Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>

 src/cf/linux-checks.m4          |   1 +
 src/cf/linux-kernel-compiler.m4 | 106 ++++++++++++++++++++++++++++++++++++++++
 src/cf/summary.m4               |   2 +
 3 files changed, 109 insertions(+)

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