stdbuf: add feat_external_libstdbuf

.cargo/config.toml

@@ -3,6 +3,8 @@ linker = "x86_64-unknown-redox-gcc"
 
 [env]
 PROJECT_NAME_FOR_VERSION_STRING = "uutils coreutils"
+# See feat_external_libstdbuf in src/uu/stdbuf/Cargo.toml
+LIBSTDBUF_DIR = "/usr/lib"
 
 # libstdbuf must be a shared library, so musl libc can't be linked statically
 # https://github.com/rust-lang/rust/issues/82193

Cargo.toml

@@ -37,6 +37,9 @@ test_risky_names = []
 # * only build `uudoc` when `--feature uudoc` is activated
 uudoc = ["zip", "dep:uuhelp_parser"]
 ## features
+## 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_acl" == enable support for ACLs (access control lists; by using`--features feat_acl`)
 # NOTE:
 # * On linux, the posix-acl/acl-sys crate requires `libacl` headers and shared library to be accessible in the C toolchain at compile time.

src/uu/stdbuf/Cargo.toml

@@ -1,3 +1,4 @@
+# spell-checker:ignore dpkg
 [package]
 name = "uu_stdbuf"
 description = "stdbuf ~ (uutils) run COMMAND with modified standard stream buffering"
@@ -23,6 +24,25 @@ libstdbuf = { package = "uu_stdbuf_libstdbuf", path = "src/libstdbuf" }
 tempfile = { workspace = true }
 uucore = { workspace = true, features = ["parser"] }
 
+# "feat_external_libstdbuf": use an external libstdbuf.so for stdbuf instead of embedding it into
+# the stdbuf binary.
+# There are 2 use-cases:
+# 1. Installation of uutils-coreutils using cargo install (e.g. from crates.io
+#    which supports only "cargo install" as installation method).  In this case,
+#    installing libstdbuf.so is impossible, because "cargo install" installs
+#    only binary programs (no cdylib), thus libstdbuf.so must be embedded into
+#    stdbuf and written to /tmp at runtime.  This is a hack, and may not work
+#    on some platforms, e.g. because the SELinux permissions may not allow
+#    stdbuf to write to /tmp, /tmp may be read-only, libstdbuf.so may not work
+#    at all without SELinux labels, etc.
+#
+# 2. Installation of uutils-coreutils using an external tool, e.g. dpkg/apt on
+#    debian. In this case, libstdbuf.so should be installed separately to its
+#    correct location and the environment variable LIBSTDBUF_DIR configures the
+#    installation directory during the build. E.g. LIBSTDBUF_DIR="/usr/lib"
+[features]
+feat_external_libstdbuf = []
+
 [[bin]]
 name = "stdbuf"
 path = "src/main.rs"

src/uu/stdbuf/build.rs

@@ -29,6 +29,26 @@ fn main() {
     println!("cargo:rerun-if-changed=build.rs");
     println!("cargo:rerun-if-changed=src/libstdbuf/src/libstdbuf.rs");
 
+    // Check for external stdbuf feature requirements
+    #[cfg(feature = "feat_external_libstdbuf")]
+    {
+        if env::var("LIBSTDBUF_DIR").is_err() {
+            eprintln!(
+                "\n\x1b[31mError:\x1b[0m The 'feat_external_libstdbuf' feature requires the LIBSTDBUF_DIR environment variable to be set."
+            );
+            eprintln!(
+                "\x1b[33mUsage:\x1b[0m LIBSTDBUF_DIR=/path/to/lib/directory cargo build --features feat_external_libstdbuf"
+            );
+            eprintln!(
+                "\x1b[33mExample:\x1b[0m LIBSTDBUF_DIR=/usr/lib cargo build --features feat_external_libstdbuf"
+            );
+            eprintln!(
+                "\nThis directory should point to where libstdbuf.so / libstdbuf.dylib will be installed on the target system."
+            );
+            std::process::exit(1);
+        }
+    }
+
     let out_dir = env::var("OUT_DIR").expect("OUT_DIR not set");
     let target = env::var("TARGET").unwrap_or_else(|_| "unknown".to_string());
 

src/uu/stdbuf/src/stdbuf.rs

@@ -6,8 +6,6 @@
 // spell-checker:ignore (ToDO) tempdir dyld dylib optgrps libstdbuf
 
 use clap::{Arg, ArgAction, ArgMatches, Command};
-use std::fs::File;
-use std::io::Write;
 use std::os::unix::process::ExitStatusExt;
 use std::path::PathBuf;
 use std::process;
@@ -29,16 +27,19 @@ mod options {
     pub const COMMAND: &str = "command";
 }
 
-#[cfg(any(
-    target_os = "linux",
-    target_os = "android",
-    target_os = "freebsd",
-    target_os = "netbsd",
-    target_os = "dragonfly"
+#[cfg(all(
+    not(feature = "feat_external_libstdbuf"),
+    any(
+        target_os = "linux",
+        target_os = "android",
+        target_os = "freebsd",
+        target_os = "netbsd",
+        target_os = "dragonfly"
+    )
 ))]
 const STDBUF_INJECT: &[u8] = include_bytes!(concat!(env!("OUT_DIR"), "/libstdbuf.so"));
 
-#[cfg(target_vendor = "apple")]
+#[cfg(all(not(feature = "feat_external_libstdbuf"), target_vendor = "apple"))]
 const STDBUF_INJECT: &[u8] = include_bytes!(concat!(env!("OUT_DIR"), "/libstdbuf.dylib"));
 
 enum BufferType {
@@ -137,7 +138,11 @@ fn set_command_env(command: &mut process::Command, buffer_name: &str, buffer_typ
     }
 }
 
+#[cfg(not(feature = "feat_external_libstdbuf"))]
 fn get_preload_env(tmp_dir: &TempDir) -> UResult<(String, PathBuf)> {
+    use std::fs::File;
+    use std::io::Write;
+
     let (preload, extension) = preload_strings()?;
     let inject_path = tmp_dir.path().join("libstdbuf").with_extension(extension);
 
@@ -147,6 +152,29 @@ fn get_preload_env(tmp_dir: &TempDir) -> UResult<(String, PathBuf)> {
     Ok((preload.to_owned(), inject_path))
 }
 
+#[cfg(feature = "feat_external_libstdbuf")]
+fn get_preload_env(_tmp_dir: &TempDir) -> UResult<(String, PathBuf)> {
+    let (preload, extension) = preload_strings()?;
+
+    // Use the directory provided at compile time via LIBSTDBUF_DIR environment variable
+    // This will fail to compile if LIBSTDBUF_DIR is not set, which is the desired behavior
+    const LIBSTDBUF_DIR: &str = env!("LIBSTDBUF_DIR");
+    let path_buf = PathBuf::from(LIBSTDBUF_DIR)
+        .join("libstdbuf")
+        .with_extension(extension);
+    if path_buf.exists() {
+        return Ok((preload.to_owned(), path_buf));
+    }
+
+    Err(USimpleError::new(
+        1,
+        format!(
+            "External libstdbuf not found at configured path: {}",
+            path_buf.display()
+        ),
+    ))
+}
+
 #[uucore::main]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     let matches = uu_app().try_get_matches_from(args).with_exit_code(125)?;