From 5ff6ac4287e191ee684f1de1af642e7b656947b6 Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Fri, 12 Nov 2021 12:58:38 -0800 Subject: Refactor weak symbols in std::sys::unix This makes a few changes to the weak symbol macros in `sys::unix`: - `dlsym!` is added to keep the functionality for runtime `dlsym` lookups, like for `__pthread_get_minstack@GLIBC_PRIVATE` that we don't want to show up in ELF symbol tables. - `weak!` now uses `#[linkage = "extern_weak"]` symbols, so its runtime behavior is just a simple null check. This is also used by `syscall!`. - On non-ELF targets (macos/ios) where that linkage is not known to behave, `weak!` is just an alias to `dlsym!` for the old behavior. - `raw_syscall!` is added to always call `libc::syscall` on linux and android, for cases like `clone3` that have no known libc wrapper. The new `weak!` linkage does mean that you'll get versioned symbols if you build with a newer glibc, like `WEAK DEFAULT UND statx@GLIBC_2.28`. This might seem problematic, but old non-weak symbols can tie the build to new versions too, like `dlsym@GLIBC_2.34` from their recent library unification. If you build with an old glibc like `dist-x86_64-linux` does, you'll still get unversioned `WEAK DEFAULT UND statx`, which may be resolved based on the runtime glibc. I also found a few functions that don't need to be weak anymore: - Android can directly use `ftruncate64`, `pread64`, and `pwrite64`, as these were added in API 12, and our baseline is API 14. - Linux can directly use `splice`, added way back in glibc 2.5 and similarly old musl. Android only added it in API 21 though. --- library/std/src/sys/unix/process/process_unix.rs | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'library/std/src/sys/unix/process/process_unix.rs') diff --git a/library/std/src/sys/unix/process/process_unix.rs b/library/std/src/sys/unix/process/process_unix.rs index 3bf1493f3b8..bce35b380e6 100644 --- a/library/std/src/sys/unix/process/process_unix.rs +++ b/library/std/src/sys/unix/process/process_unix.rs @@ -13,7 +13,7 @@ use crate::sys::process::process_common::*; use crate::os::linux::process::PidFd; #[cfg(target_os = "linux")] -use crate::sys::weak::syscall; +use crate::sys::weak::raw_syscall; #[cfg(any( target_os = "macos", @@ -162,7 +162,7 @@ impl Command { cgroup: u64, } - syscall! { + raw_syscall! { fn clone3(cl_args: *mut clone_args, len: libc::size_t) -> libc::c_long } -- cgit 1.4.1-3-g733a5