utmpx: fall back to systemd-logind on Linux when traditional utmp is empty/unavailable

.github/workflows/freebsd.yml

@@ -183,9 +183,8 @@ jobs:
           export RUST_BACKTRACE=1
           export CARGO_TERM_COLOR=always
           if (test -z "\$FAULT"); then cargo nextest run --hide-progress-bar --profile ci --features '${{ matrix.job.features }}' || FAULT=1 ; fi
-          # There is no systemd-logind on FreeBSD, so test all features except feat_systemd_logind ( https://github.com/rust-lang/cargo/issues/3126#issuecomment-2523441905 )
           if (test -z "\$FAULT"); then
-            UUCORE_FEATURES=\$(cargo metadata --format-version=1 --no-deps | jq -r '.packages[] | select(.name == "uucore") | .features | keys | .[]' | grep -v "feat_systemd_logind" | paste -s -d "," -)
+            UUCORE_FEATURES=\$(cargo metadata --format-version=1 --no-deps | jq -r '.packages[] | select(.name == "uucore") | .features | keys | .[]' | paste -s -d "," -)
             cargo nextest run --hide-progress-bar --profile ci --features "\$UUCORE_FEATURES" -p uucore || FAULT=1
           fi
           # Test building with make

.github/workflows/openbsd.yml

@@ -215,10 +215,9 @@ jobs:
             cargo test --features '${{ matrix.job.features }}' || FAULT=1
             echo "::endgroup::"
           fi
-          # There is no systemd-logind on OpenBSD, so test all features except feat_systemd_logind
           if (test -z "\$FAULT"); then
             echo "::group::cargo test (uucore)"
-            UUCORE_FEATURES=\$(cargo metadata --format-version=1 --no-deps | jq -r '.packages[] | select(.name == "uucore") | .features | keys | .[]' | grep -v "feat_systemd_logind" | paste -s -d "," -)
+            UUCORE_FEATURES=\$(cargo metadata --format-version=1 --no-deps | jq -r '.packages[] | select(.name == "uucore") | .features | keys | .[]' | paste -s -d "," -)
             cargo test --features "\$UUCORE_FEATURES" -p uucore || FAULT=1
             echo "::endgroup::"
           fi

.vscode/cspell.dictionaries/workspace.wordlist.txt

@@ -1,6 +1,7 @@
 # * cargo
 cdylib
 doctest
+libloading
 
 # * uutils project
 uutils
@@ -186,6 +187,7 @@ execvp
 fdatasync
 freeaddrinfo
 getaddrinfo
+dlopen
 getegid
 geteuid
 getgid
@@ -201,6 +203,7 @@ inode
 inodes
 isatty
 lchown
+libsystemd
 pathlen
 setgid
 setgroups

Cargo.toml

@@ -84,6 +84,7 @@ jiff = "0.2.18"
 jiff-icu = "0.2.2"
 jiff-tzdb = "0.1"
 libc = "0.2.186"
+libloading = "0.8.9"
 lscolors = { version = "0.21.0", default-features = false, features = [
   "gnu_legacy",
 ] }
@@ -454,14 +455,6 @@ feat_diagnostics = ["uucore/diagnostics"]
 ## Optional feature for stdbuf
 # "feat_external_libstdbuf" == use an external libstdbuf.so for stdbuf instead of embedding it
 feat_external_libstdbuf = ["stdbuf/feat_external_libstdbuf"]
-# "feat_systemd_logind" == enable feat_systemd_logind support for utmpx replacement
-feat_systemd_logind = [
-  "pinky/feat_systemd_logind",
-  "uptime/feat_systemd_logind",
-  "users/feat_systemd_logind",
-  "uucore/feat_systemd_logind",
-  "who/feat_systemd_logind",
-]
 # "feat_selinux" == enable support for SELinux Security Context (by using `--features feat_selinux`)
 # NOTE:
 # * The selinux(-sys) crate requires `libselinux` headers and shared library to be accessible in the C toolchain at compile time.

src/uu/pinky/Cargo.toml

@@ -22,9 +22,6 @@ clap = { workspace = true }
 fluent = { workspace = true }
 uucore = { workspace = true, features = ["utmpx", "entries"] }
 
-[features]
-feat_systemd_logind = ["uucore/feat_systemd_logind"]
-
 [lints]
 workspace = true
 

src/uu/uptime/Cargo.toml

@@ -25,9 +25,6 @@ jiff = { workspace = true }
 thiserror = { workspace = true }
 uucore = { workspace = true, features = ["libc", "utmpx", "uptime"] }
 
-[features]
-feat_systemd_logind = ["uucore/feat_systemd_logind"]
-
 [lints]
 workspace = true
 

src/uu/users/Cargo.toml

@@ -29,9 +29,6 @@ uucore = { workspace = true, features = [] }
 [target.'cfg(target_os = "openbsd")'.dependencies]
 utmp-classic = { workspace = true }
 
-[features]
-feat_systemd_logind = ["uucore/feat_systemd_logind"]
-
 [lints]
 workspace = true
 

src/uu/who/Cargo.toml

@@ -24,9 +24,6 @@ fluent = { workspace = true }
 rustix = { workspace = true, features = ["fs", "termios"] }
 uucore = { workspace = true, features = ["utmpx"] }
 
-[features]
-feat_systemd_logind = ["uucore/feat_systemd_logind"]
-
 [lints]
 workspace = true
 

src/uucore/Cargo.toml

@@ -117,6 +117,7 @@ time = { workspace = true, optional = true, features = [
 walkdir = { workspace = true, optional = true }
 
 [target.'cfg(target_os = "linux")'.dependencies]
+libloading = { workspace = true, optional = true }
 procfs = { workspace = true, optional = true }
 
 [target.'cfg(windows)'.dependencies]
@@ -164,7 +165,6 @@ fsext = ["libc", "windows-sys", "bstr", "wide"]
 fsxattr = ["xattr", "itertools", "libc"]
 hardware = []
 lines = []
-feat_systemd_logind = ["utmpx", "libc"]
 format = [
   "bigdecimal",
   "extendedbigdecimal",
@@ -225,7 +225,7 @@ sum = [
 openssl = ["dep:openssl"]
 update-control = ["parser"]
 utf8 = []
-utmpx = ["time", "time/macros", "libc", "dns-lookup"]
+utmpx = ["time", "time/macros", "libc", "dns-lookup", "dep:libloading"]
 version-cmp = []
 wide = []
 tty = []

src/uucore/src/lib/features.rs

@@ -128,7 +128,7 @@ pub mod selinux;
 pub mod signals;
 #[cfg(all(feature = "smack", target_os = "linux"))]
 pub mod smack;
-#[cfg(feature = "feat_systemd_logind")]
+#[cfg(all(target_os = "linux", feature = "utmpx"))]
 pub mod systemd_logind;
 #[cfg(all(
     feature = "utmpx",