From a06edda3ad9abd4f07d07bbe46cb488efeebbbd0 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Wed, 9 Sep 2020 10:16:03 -0400
Subject: [PATCH 1/2] Fix segfault if pthread_getattr_np fails

glibc destroys[1] the passed pthread_attr_t if pthread_getattr_np()
fails.  Destroying it again leads to a segfault.  Fix it by only
destroying it on success for glibc.

[1]: https://sourceware.org/git/?p=glibc.git;a=blob;f=nptl/pthread_getattr_np.c;h=ce437205e41dc05653e435f6188768cccdd91c99;hb=HEAD#l205
---
 library/std/src/sys/unix/thread.rs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/library/std/src/sys/unix/thread.rs b/library/std/src/sys/unix/thread.rs
index 04da9812ddc45..569aedd741192 100644
--- a/library/std/src/sys/unix/thread.rs
+++ b/library/std/src/sys/unix/thread.rs
@@ -305,7 +305,9 @@ pub mod guard {
             assert_eq!(libc::pthread_attr_getstack(&attr, &mut stackaddr, &mut stacksize), 0);
             ret = Some(stackaddr);
         }
-        assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
+        if e == 0 || cfg!(not(target_env = "gnu")) {
+            assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
+        }
         ret
     }
 
@@ -446,7 +448,9 @@ pub mod guard {
                 Some(stackaddr..stackaddr + guardsize)
             };
         }
-        assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
+        if e == 0 || cfg!(not(target_env = "gnu")) {
+            assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
+        }
         ret
     }
 }

From a684153f2920729f9fc3ea27ddb77d7cc3543214 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Wed, 9 Sep 2020 11:10:43 -0400
Subject: [PATCH 2/2] Only call pthread_attr_destroy() after getattr_np()
 succeeds on all libcs

The calling convention of pthread_getattr_np() is to initialize the
pthread_attr_t, so _destroy() is only necessary on success (and _init()
isn't necessary beforehand).  On the other hand, FreeBSD wants the
attr_t to be initialized before pthread_attr_get_np(), and therefore it
should always be destroyed afterwards.
---
 library/std/src/sys/unix/thread.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/library/std/src/sys/unix/thread.rs b/library/std/src/sys/unix/thread.rs
index 569aedd741192..652219e28f6e0 100644
--- a/library/std/src/sys/unix/thread.rs
+++ b/library/std/src/sys/unix/thread.rs
@@ -294,6 +294,7 @@ pub mod guard {
     unsafe fn get_stack_start() -> Option<*mut libc::c_void> {
         let mut ret = None;
         let mut attr: libc::pthread_attr_t = crate::mem::zeroed();
+        #[cfg(target_os = "freebsd")]
         assert_eq!(libc::pthread_attr_init(&mut attr), 0);
         #[cfg(target_os = "freebsd")]
         let e = libc::pthread_attr_get_np(libc::pthread_self(), &mut attr);
@@ -305,7 +306,7 @@ pub mod guard {
             assert_eq!(libc::pthread_attr_getstack(&attr, &mut stackaddr, &mut stacksize), 0);
             ret = Some(stackaddr);
         }
-        if e == 0 || cfg!(not(target_env = "gnu")) {
+        if e == 0 || cfg!(target_os = "freebsd") {
             assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
         }
         ret
@@ -405,6 +406,7 @@ pub mod guard {
     pub unsafe fn current() -> Option<Guard> {
         let mut ret = None;
         let mut attr: libc::pthread_attr_t = crate::mem::zeroed();
+        #[cfg(target_os = "freebsd")]
         assert_eq!(libc::pthread_attr_init(&mut attr), 0);
         #[cfg(target_os = "freebsd")]
         let e = libc::pthread_attr_get_np(libc::pthread_self(), &mut attr);
@@ -448,7 +450,7 @@ pub mod guard {
                 Some(stackaddr..stackaddr + guardsize)
             };
         }
-        if e == 0 || cfg!(not(target_env = "gnu")) {
+        if e == 0 || cfg!(target_os = "freebsd") {
             assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
         }
         ret