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Posted to issues@stdcxx.apache.org by "Liviu Nicoara (JIRA)" <ji...@apache.org> on 2012/09/28 14:12:08 UTC
[jira] [Commented] (STDCXX-1072) [Oracle Solaris/SPARCV8] stricter
mutex alignment requirements
[ https://issues.apache.org/jira/browse/STDCXX-1072?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13465554#comment-13465554 ]
Liviu Nicoara commented on STDCXX-1072:
---------------------------------------
The kernel patch changed the alignment of the userland mutex objects from a machine word to a double-word boundary. No changes are required of the users who use such objects in their programs unless users create mutex objects in buffers which may not be aligned on a proper boundary. E.g., the following are safe:
{noformat}
mutex_t lock;
struct S {
char misalign;
mutex_t lock;
};
{noformat}
whereas the following is not:
{noformat}
union {
void* align;
char buf [sizeof mutex_t];
} u;
new (&u) mutex_t;
{noformat}
because the alignment requirements for void pointer are less strict than for mutex_t. A few places in the library use the latter for all sorts of static objects (mostly local statics).
> [Oracle Solaris/SPARCV8] stricter mutex alignment requirements
> --------------------------------------------------------------
>
> Key: STDCXX-1072
> URL: https://issues.apache.org/jira/browse/STDCXX-1072
> Project: C++ Standard Library
> Issue Type: Bug
> Components: Thread Safety
> Affects Versions: 4.1.2, 4.1.3, 4.1.4, 4.2.0, 4.2.1
> Environment: Oracle Solaris on SPARC V8 (or V9 emulation?) hardware.
> Reporter: Liviu Nicoara
> Labels: SPARC, Solaris, V8, alignment, mutex
> Fix For: 4.2.x, 4.3.x, 5.0.0
>
> Original Estimate: 4h
> Remaining Estimate: 4h
>
> The issue has been reported in STDCXX-1066. The originator was apparently an improvement (as a response to CR 6296770: http://tinyurl.com/8ohjsgl) shipped with KU 137111-01 (http://tinyurl.com/ceet6ec) which requires stricter alignment than the machine word for userland mutexes.
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