[PATCH 0/2] fix AT_RENAME_* redefinitions with glibc < 2.43

[Masaharu Noguchi <nogunix@gmail.com>]

LKML reports show that `allyesconfig` currently fails with glibc 2.42
because both `<stdio.h>` and `<linux/fcntl.h>` define the AT_RENAME_*
macros.  A follow-up pointed to glibc commit `1166170d9586 ("libio:
Define AT_RENAME_* with the same tokens as Linux")`, which will first
appear in glibc 2.43.  Until that release lands in common distributions,
upstream kernels still build against glibc versions that redeclare the
macros and fail under `-Werror`.

This series is a small, revertable workaround so developers on Fedora 43
(glibc 2.42) and other distributions with glibc < 2.43 can keep building
the samples.  The
first patch only emits the AT_RENAME_* aliases when libc does not do so
already, and the second patch undefines any libc-provided macros before
including `<linux/fcntl.h>` in the VFS sample.  Once glibc 2.43+ is
ubiquitous (or if we decide to remove the aliases entirely), these
changes can be dropped.

Link: https://lore.kernel.org/all/CAHaCkme7C8LDpWVX8TnDQQ+feWeQy_SA3HYfpyyPNFee_+Z2EA@mail.gmail.com/ # LKML report
Link: https://lore.kernel.org/all/20251013012423.GA331@ax162/ # follow-up
Link: https://sourceware.org/git/?p=glibc.git;a=commit;h=1166170d95863e5a6f8121a5ca9d97713f524f49 # glibc fix

Masaharu Noguchi (2):
  uapi: fcntl: guard AT_RENAME_* aliases
  samples: vfs: avoid libc AT_RENAME_* redefinitions

 include/uapi/linux/fcntl.h | 6 ++++++
 samples/vfs/test-statx.c   | 9 +++++++++
 2 files changed, 15 insertions(+)

-- 
2.51.1