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Get __pthread_get_minstack at runtime with dlsym

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Linking __pthread_get_minstack, even weakly, was causing Debian’s
dpkg-shlibdeps to detect an unnecessarily strict versioned dependency
on libc6.

Closes #23628.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
This commit is contained in:
Anders Kaseorg
2015-03-23 00:58:19 -04:00
parent b0aad7dd4f
commit 0090e01f08
1 changed files with 23 additions and 12 deletions
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33
src/libstd/sys/unix/thread.rs
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@@ -13,12 +13,14 @@
use core::prelude::*; use core::prelude::*;
use cmp; use cmp;
use dynamic_lib::DynamicLibrary;
use ffi::CString; use ffi::CString;
use io; use io;
use libc::consts::os::posix01::PTHREAD_STACK_MIN; use libc::consts::os::posix01::PTHREAD_STACK_MIN;
use libc; use libc;
use mem; use mem;
use ptr; use ptr;
use sync::{Once, ONCE_INIT};
use sys::os; use sys::os;
use thunk::Thunk; use thunk::Thunk;
use time::Duration; use time::Duration;
@@ -314,21 +316,30 @@ pub fn sleep(dur: Duration) {
// is created in an application with big thread-local storage requirements. // is created in an application with big thread-local storage requirements.
// See #6233 for rationale and details. // See #6233 for rationale and details.
// //
// Link weakly to the symbol for compatibility with older versions of glibc. // Use dlsym to get the symbol value at runtime, for compatibility
// Assumes that we've been dynamically linked to libpthread but that is // with older versions of glibc. Assumes that we've been dynamically
// currently always the case. Note that you need to check that the symbol // linked to libpthread but that is currently always the case. We
// is non-null before calling it! // previously used weak linkage (under the same assumption), but that
// caused Debian to detect an unnecessarily strict versioned
// dependency on libc6 (#23628).
#[cfg(target_os = "linux")] #[cfg(target_os = "linux")]
fn min_stack_size(attr: *const libc::pthread_attr_t) -> libc::size_t { fn min_stack_size(attr: *const libc::pthread_attr_t) -> libc::size_t {
type F = unsafe extern "C" fn(*const libc::pthread_attr_t) -> libc::size_t; type F = unsafe extern "C" fn(*const libc::pthread_attr_t) -> libc::size_t;
extern { static INIT: Once = ONCE_INIT;
#[linkage = "extern_weak"] static mut __pthread_get_minstack: Option<F> = None;
static __pthread_get_minstack: *const ();
INIT.call_once(|| {
let lib = DynamicLibrary::open(None).unwrap();
unsafe {
if let Ok(f) = lib.symbol("__pthread_get_minstack") {
__pthread_get_minstack = Some(mem::transmute::<*const (), F>(f));
} }
if __pthread_get_minstack.is_null() { }
PTHREAD_STACK_MIN });
} else {
unsafe { mem::transmute::<*const (), F>(__pthread_get_minstack)(attr) } match unsafe { __pthread_get_minstack } {
None => PTHREAD_STACK_MIN,
Some(f) => unsafe { f(attr) },
} }
} }