Put program::at_exit and thread::at_exit behind feature flags. (#141)

This allow them to be excluded when not needed, reducing code size.

Author: sunfishcode

Cargo.toml

@@ -58,7 +58,7 @@ features = ["param"]
 assert_cmd = "2.0.12"
 
 [features]
-default = ["std", "log", "libc", "errno", "thread", "init-fini-arrays"]
+default = ["std", "log", "libc", "errno", "thread", "init-fini-arrays", "program-at-exit", "thread-at-exit"]
 std = ["rustix/std", "bitflags/std", "alloc"]
 rustc-dep-of-std = [
     "dep:core",
@@ -89,8 +89,8 @@ external-start = ["take-charge"]
 # The loggers depend on a `.init_array` entry to initialize themselves, and
 # `env_logger` needs it so that `c-scape` can initialize environment variables
 # and make `RUST_LOG` available.
-atomic-dbg-logger = ["atomic-dbg/log", "init-fini-arrays"]
-env_logger = ["dep:env_logger", "init-fini-arrays"]
+atomic-dbg-logger = ["atomic-dbg/log", "init-array"]
+env_logger = ["dep:env_logger", "init-array"]
 
 # Disable logging.
 max_level_off = ["log/max_level_off"]
@@ -105,7 +105,7 @@ thread = ["rustix/thread", "rustix/mm", "param", "rustix/process", "rustix/runti
 # Enable support for signal handlers.
 signal = ["rustix/runtime"]
 
-# Enable support for `rustix::param`.
+# Have origin call `rustix::param::init`.
 param = ["rustix/param"]
 
 # Enable support for ELF `.init_array` and `.fini_array`.
@@ -117,6 +117,12 @@ init-array = []
 # Enable support for ELF `.fini_array`.
 fini-array = []
 
+# Enable support for `origin::program::at_exit`.
+program-at-exit = ["alloc"]
+
+# Enable support for `origin::thread::at_exit`.
+thread-at-exit = ["alloc", "thread"]
+
 # Enable highly experimental support for performing startup-time relocations,
 # needed to support statically-linked PIE executables.
 experimental-relocate = ["rustix/mm", "rustix/runtime"]
@@ -171,4 +177,4 @@ panic-handler-abort = ["unwinding?/panic-handler-dummy"]
 getauxval = ["rustix/param"]
 
 [package.metadata.docs.rs]
-features = ["take-charge", "origin-start", "thread", "signal", "nightly"]
+features = ["origin-start", "thread", "signal", "program-at-exit", "thread-at-exit", "nightly"]

example-crates/external-start/Cargo.toml

@@ -7,7 +7,7 @@ publish = false
 [dependencies]
 # Origin can be depended on just like any other crate. For no_std, disable
 # the default features, and the desired features.
-origin = { path = "../..", default-features = false, features = ["take-charge", "external-start", "thread", "alloc", "eh-personality-continue", "panic-handler-abort", "nightly"] }
+origin = { path = "../..", default-features = false, features = ["take-charge", "external-start", "thread", "alloc", "program-at-exit", "thread-at-exit", "eh-personality-continue", "panic-handler-abort", "nightly"] }
 
 # Ensure that libc gets linked.
 libc = { version = "0.2", default-features = false }

example-crates/no-std/Cargo.toml

@@ -7,7 +7,7 @@ publish = false
 [dependencies]
 # Origin can be depended on just like any other crate. For no_std, disable
 # the default features. And enable "libc" to enable the libc implementations.
-origin = { path = "../..", default-features = false, features = ["libc", "thread", "alloc", "eh-personality-continue", "panic-handler-abort", "nightly"] }
+origin = { path = "../..", default-features = false, features = ["libc", "thread", "alloc", "program-at-exit", "thread-at-exit", "eh-personality-continue", "panic-handler-abort", "nightly"] }
 
 # Crates to help writing no_std code.
 atomic-dbg = { version = "0.1.8", default-features = false }

example-crates/origin-start-dynamic-linker/Cargo.toml

@@ -10,7 +10,7 @@ crate-type = ["cdylib"]
 [dependencies]
 # Origin can be depended on just like any other crate. For no_std, disable
 # the default features, and the desired features.
-origin = { path = "../..", default-features = false, features = ["take-charge", "origin-start", "thread", "alloc", "experimental-relocate", "eh-personality-continue", "panic-handler-abort", "nightly"] }
+origin = { path = "../..", default-features = false, features = ["origin-start", "thread", "alloc", "program-at-exit", "thread-at-exit", "experimental-relocate", "eh-personality-continue", "panic-handler-abort", "nightly"] }
 
 # Crates to help writing no_std code.
 atomic-dbg = { version = "0.1.8", default-features = false }

example-crates/origin-start-lto/Cargo.toml

@@ -7,7 +7,7 @@ publish = false
 [dependencies]
 # Origin can be depended on just like any other crate. For no_std, disable
 # the default features, and the desired features.
-origin = { path = "../..", default-features = false, features = ["take-charge", "origin-start", "thread", "alloc", "eh-personality-continue", "panic-handler-abort", "nightly"] }
+origin = { path = "../..", default-features = false, features = ["origin-start", "thread", "alloc", "program-at-exit", "thread-at-exit", "eh-personality-continue", "panic-handler-abort", "nightly"] }
 
 # Crates to help writing no_std code.
 atomic-dbg = { version = "0.1.8", default-features = false }

example-crates/origin-start-stable/Cargo.toml

@@ -7,7 +7,7 @@ publish = false
 [dependencies]
 # Origin can be depended on just like any other crate. For no_std, disable
 # the default features, and the desired features.
-origin = { path = "../..", default-features = false, features = ["take-charge", "origin-start", "thread", "alloc", "eh-personality-continue", "panic-handler-abort"] }
+origin = { path = "../..", default-features = false, features = ["origin-start", "thread", "alloc", "program-at-exit", "thread-at-exit", "eh-personality-continue", "panic-handler-abort"] }
 
 # Crates to help writing no_std code.
 atomic-dbg = { version = "0.1.8", default-features = false }

example-crates/origin-start/Cargo.toml

@@ -7,7 +7,7 @@ publish = false
 [dependencies]
 # Origin can be depended on just like any other crate. For no_std, disable
 # the default features, and the desired features.
-origin = { path = "../..", default-features = false, features = ["take-charge", "origin-start", "thread", "alloc", "eh-personality-continue", "panic-handler-abort", "nightly"] }
+origin = { path = "../..", default-features = false, features = ["origin-start", "thread", "alloc", "program-at-exit", "thread-at-exit", "eh-personality-continue", "panic-handler-abort", "nightly"] }
 
 # Crates to help writing no_std code.
 atomic-dbg = { version = "0.1.8", default-features = false }

src/program/libc.rs

@@ -28,14 +28,15 @@
 //! with origin's goal of providing Rust-idiomatic interfaces, however it does
 //! mean that origin can avoid doing any work that users might not need.
 
-#[cfg(feature = "alloc")]
+#[cfg(feature = "program-at-exit")]
 use alloc::boxed::Box;
+#[cfg(feature = "program-at-exit")]
 use core::ptr::null_mut;
 use linux_raw_sys::ctypes::c_int;
 
 /// Register a function to be called when [`exit`] is called.
-#[cfg(feature = "alloc")]
-#[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
+#[cfg(feature = "program-at-exit")]
+#[cfg_attr(docsrs, doc(cfg(feature = "program-at-exit")))]
 pub fn at_exit(func: Box<dyn FnOnce() + Send>) {
     use core::ffi::c_void;
 

src/program/linux_raw.rs

@@ -30,12 +30,12 @@
 
 #[cfg(feature = "thread")]
 use crate::thread;
-#[cfg(feature = "alloc")]
+#[cfg(feature = "program-at-exit")]
 use alloc::boxed::Box;
-#[cfg(all(feature = "alloc", not(feature = "thread")))]
+#[cfg(all(feature = "program-at-exit", not(feature = "thread")))]
 use core::cell::UnsafeCell;
 use linux_raw_sys::ctypes::c_int;
-#[cfg(all(feature = "alloc", feature = "thread"))]
+#[cfg(all(feature = "program-at-exit", feature = "thread"))]
 use rustix_futex_sync::Mutex;
 
 #[cfg(not(any(feature = "origin-start", feature = "external-start")))]
@@ -227,28 +227,28 @@ unsafe fn init_runtime(mem: *mut usize, envp: *mut *mut u8) {
 /// `SmallVec` to ensure we can register that many without allocating.
 ///
 /// [POSIX guarantees]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/atexit.html
-#[cfg(all(feature = "alloc", feature = "thread"))]
+#[cfg(all(feature = "program-at-exit", feature = "thread"))]
 static DTORS: Mutex<smallvec::SmallVec<[Box<dyn FnOnce() + Send>; 32]>> =
     Mutex::new(smallvec::SmallVec::new_const());
 
 /// A type for `DTORS` in the single-threaded case that we can mark as `Sync`.
-#[cfg(all(feature = "alloc", not(feature = "thread")))]
+#[cfg(all(feature = "program-at-exit", not(feature = "thread")))]
 struct Dtors(UnsafeCell<smallvec::SmallVec<[Box<dyn FnOnce() + Send>; 32]>>);
 
 /// SAFETY: With `feature = "take-charge"`, we can assume that Origin is
 /// responsible for creating all threads in the program, and with
 /// `not(feature = "thread")` mode, Origin can't create any new threads, so we
 /// don't need to synchronize.
-#[cfg(all(feature = "alloc", not(feature = "thread")))]
+#[cfg(all(feature = "program-at-exit", not(feature = "thread")))]
 unsafe impl Sync for Dtors {}
 
 /// The single-threaded version of `DTORS`.
-#[cfg(all(feature = "alloc", not(feature = "thread")))]
+#[cfg(all(feature = "program-at-exit", not(feature = "thread")))]
 static DTORS: Dtors = Dtors(UnsafeCell::new(smallvec::SmallVec::new_const()));
 
 /// Register a function to be called when [`exit`] is called.
-#[cfg(feature = "alloc")]
-#[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
+#[cfg(feature = "program-at-exit")]
+#[cfg_attr(docsrs, doc(cfg(feature = "program-at-exit")))]
 pub fn at_exit(func: Box<dyn FnOnce() + Send>) {
     #[cfg(feature = "thread")]
     let mut dtors = DTORS.lock();
@@ -263,13 +263,13 @@ pub fn at_exit(func: Box<dyn FnOnce() + Send>) {
 /// `.fini_array` section, and exit the program.
 pub fn exit(status: c_int) -> ! {
     // Call functions registered with `at_thread_exit`.
-    #[cfg(all(feature = "alloc", feature = "thread"))]
+    #[cfg(feature = "thread-at-exit")]
     crate::thread::call_dtors(crate::thread::current());
 
     // Call all the registered functions, in reverse order. Leave `DTORS`
     // unlocked while making the call so that functions can add more functions
     // to the end of the list.
-    #[cfg(feature = "alloc")]
+    #[cfg(feature = "program-at-exit")]
     loop {
         #[cfg(feature = "thread")]
         let mut dtors = DTORS.lock();

src/thread/libc.rs

@@ -2,6 +2,7 @@
 
 #[cfg(not(feature = "nightly"))]
 use crate::ptr::{with_exposed_provenance_mut, without_provenance_mut, Polyfill as _};
+#[cfg(feature = "thread-at-exit")]
 use alloc::boxed::Box;
 use core::ffi::{c_int, c_void};
 use core::mem::{size_of, transmute, zeroed};
@@ -23,6 +24,7 @@ extern "C" {
     fn __errno_location() -> *mut c_int;
     fn __tls_get_addr(p: &[usize; 2]) -> *mut c_void;
 
+    #[cfg(feature = "thread-at-exit")]
     static __dso_handle: *const c_void;
 }
 
@@ -154,6 +156,7 @@ pub unsafe fn create(
 }
 
 /// Registers a function to call when the current thread exits.
+#[cfg(feature = "thread-at-exit")]
 pub fn at_exit(func: Box<dyn FnOnce()>) {
     extern "C" fn call(arg: *mut c_void) {
         unsafe {
@@ -322,6 +325,7 @@ pub fn yield_current() {
 }
 
 /// Return the address of `__dso_handle`, appropriately casted.
+#[cfg(feature = "thread-at-exit")]
 unsafe fn dso_handle() -> *mut c_void {
     let dso_handle: *const *const c_void = &__dso_handle;
     dso_handle.cast::<c_void>().cast_mut()