From c0c13d73233c740b7d278c71b161da7b16217564 Mon Sep 17 00:00:00 2001
From: Sergei Trofimovich <slyich@gmail.com>
Date: Fri, 16 Jan 2026 22:48:25 +0000
Subject: [PATCH] libutil: fix `linux` build on fresh `glibc` and `gcc`

Without the change the build fails for me as:

    ../unix/file-descriptor.cc:404:70: error: 'RESOLVE_BENEATH' was not declared in this scope
      404 |         dirFd, path.rel_c_str(), flags, static_cast<uint64_t>(mode), RESOLVE_BENEATH | RESOLVE_NO_SYMLINKS);
          |                                                                      ^~~~~~~~~~~~~~~

This happens for 2 reasons:
1. `__NR_openat2` constant was not pulled in from the according headers
   and as a result `<linux/openat2.h>` was not included.
2. `define HAVE_OPENAT2 0` build is broken: refers to missing
   `RESOLVE_BENEATH` normally pulled in from `<linux/openat2.h>`

This changes fixes both.

(cherry picked from commit 3256aba6a2c9cc970bffd54fd13bc6a19367ffbf)
---
 src/libutil/unix/file-descriptor.cc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/libutil/unix/file-descriptor.cc b/src/libutil/unix/file-descriptor.cc
index d90342ff0ec..501f07aec65 100644
--- a/src/libutil/unix/file-descriptor.cc
+++ b/src/libutil/unix/file-descriptor.cc
@@ -8,9 +8,12 @@
 #include <unistd.h>
 #include <poll.h>
 
+#if defined(__linux__)
+#  include <sys/syscall.h> /* pull __NR_* definitions */
+#endif
+
 #if defined(__linux__) && defined(__NR_openat2)
 #  define HAVE_OPENAT2 1
-#  include <sys/syscall.h>
 #  include <linux/openat2.h>
 #else
 #  define HAVE_OPENAT2 0
@@ -323,7 +326,7 @@ Descriptor unix::openFileEnsureBeneathNoSymlinks(Descriptor dirFd, const CanonPa
 {
     assert(!path.rel().starts_with('/')); /* Just in case the invariant is somehow broken. */
     assert(!path.isRoot());
-#ifdef __linux__
+#if HAVE_OPENAT2
     auto maybeFd = linux::openat2(
         dirFd, path.rel_c_str(), flags, static_cast<uint64_t>(mode), RESOLVE_BENEATH | RESOLVE_NO_SYMLINKS);
     if (maybeFd) {