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pthread: Document the setstack vs setguardsize bug. 

Suggest the safe, compatible workaround.
This commit is contained in:
riastradh 2023-12-07 16:55:01 +00:00
parent 29fd213712
commit 57b4a3d756
2 changed files with 50 additions and 2 deletions
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26
lib/libpthread/pthread_attr_getguardsize.3
View File

@ -1,4 +1,4 @@
.\" $NetBSD: pthread_attr_getguardsize.3,v 1.5 2017/10/22 16:37:24 abhinav Exp $
.\" $NetBSD: pthread_attr_getguardsize.3,v 1.6 2023/12/07 16:55:01 riastradh Exp $
.\"
.\" Copyright (c) 2010 Jukka Ruohonen <jruohonen@iki.fi>
.\" All rights reserved.
@ -123,3 +123,27 @@ There was insufficient memory.
.Sh STANDARDS
Both functions conform to
.St -p1003.1-2008 .
.Sh BUGS
Older versions of
.Nx ,
prior to 10.0, 9.4, and 8.3, incorrectly adjust the stack address by
the guard size in threads configured with
.Xr pthread_attr_setstack 3 ,
instead of ignoring the guard size in that case as
.Tn POSIX
prescribes
.Po
see
.Lk https://gnats.NetBSD.org/57721 "PR lib/57721"
.Pc .
.Pp
Even if you didn't set a nonzero guard size with
.Fn pthread_attr_setguardsize ,
the system will choose a nonzero default guard size.
.Pp
To work around this in applications that run on older and newer
versions of
.Nx ,
as well as on other operating systems, you can safely set the guard
size to zero:
.Dl "pthread_attr_setguardsize(&attr, 0);"

26
lib/libpthread/pthread_attr_getstack.3
View File

@ -1,4 +1,4 @@
.\" $NetBSD: pthread_attr_getstack.3,v 1.8 2017/10/23 01:03:23 wiz Exp $
.\" $NetBSD: pthread_attr_getstack.3,v 1.9 2023/12/07 16:55:01 riastradh Exp $
.\"
.\" Copyright (c) 2010 Jukka Ruohonen <jruohonen@iki.fi>
.\" All rights reserved.
@ -177,3 +177,27 @@ and
were however removed from the specification in the
.St -p1003.1-2008
revision.
.Sh BUGS
Older versions of
.Nx ,
prior to 10.0, 9.4, and 8.3, incorrectly adjust the stack address by
the guard size in threads configured with
.Fn pthread_attr_setstack ,
instead of ignoring the guard size in that case as
.Tn POSIX
prescribes
.Po
see
.Lk https://gnats.NetBSD.org/57721 "PR lib/57721"
.Pc .
.Pp
Even if you didn't set a nonzero guard size with
.Xr pthread_attr_setguardsize 3 ,
the system will choose a nonzero default guard size.
.Pp
To work around this in applications that run on older and newer
versions of
.Nx ,
as well as on other operating systems, you can safely set the guard
size to zero:
.Dl "pthread_attr_setguardsize(&attr, 0);"