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rollup merge of #23631: andersk/minstack-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.
This commit is contained in:
Alex Crichton 2015-03-23 15:11:05 -07:00
commit 28fcdc0df7
1 changed files with 26 additions and 14 deletions
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40
src/libstd/sys/unix/thread.rs
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@ -13,12 +13,14 @@
use core::prelude::*;
use cmp;
use dynamic_lib::DynamicLibrary;
use ffi::CString;
use io;
use libc::consts::os::posix01::PTHREAD_STACK_MIN;
use libc;
use mem;
use ptr;
use sync::{Once, ONCE_INIT};
use sys::os;
use thunk::Thunk;
use time::Duration;
@ -314,26 +316,36 @@ pub fn sleep(dur: Duration) {
// is created in an application with big thread-local storage requirements.
// See #6233 for rationale and details.
//
// Link weakly to the symbol for compatibility with older versions of glibc.
// Assumes that we've been dynamically linked to libpthread but that is
// currently always the case. Note that you need to check that the symbol
// is non-null before calling it!
// Use dlsym to get the symbol value at runtime, both for
// compatibility with older versions of glibc, and to avoid creating
// dependencies on GLIBC_PRIVATE symbols. Assumes that we've been
// dynamically linked to libpthread but that is currently always the
// case. We 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")]
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;
extern {
#[linkage = "extern_weak"]
static __pthread_get_minstack: *const ();
}
if __pthread_get_minstack.is_null() {
PTHREAD_STACK_MIN
} else {
unsafe { mem::transmute::<*const (), F>(__pthread_get_minstack)(attr) }
static INIT: Once = ONCE_INIT;
static mut __pthread_get_minstack: Option<F> = None;
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));
}
}
});
match unsafe { __pthread_get_minstack } {
None => PTHREAD_STACK_MIN,
Some(f) => unsafe { f(attr) },
}
}
// __pthread_get_minstack() is marked as weak but extern_weak linkage is
// not supported on OS X, hence this kludge...
// No point in looking up __pthread_get_minstack() on non-glibc
// platforms.
#[cfg(not(target_os = "linux"))]
fn min_stack_size(_: *const libc::pthread_attr_t) -> libc::size_t {
PTHREAD_STACK_MIN