[Mesa-dev] [PATCH] c11/threads: initialize timeout structure

[Jose Fonseca]

On 06/10/15 20:30, Ian Romanick wrote:
> On 10/06/2015 12:04 PM, Matt Turner wrote:
>> On Sat, Oct 3, 2015 at 5:19 PM, Jan Vesely <jano.vesely at gmail.com> wrote:
>>> Signed-off-by: Jan Vesely <jano.vesely at gmail.com>
>>> ---
>>>   include/c11/threads_posix.h | 6 ++++++
>>>   1 file changed, 6 insertions(+)
>>>
>>> diff --git a/include/c11/threads_posix.h b/include/c11/threads_posix.h
>>> index 3def6c4..ce9853b 100644
>>> --- a/include/c11/threads_posix.h
>>> +++ b/include/c11/threads_posix.h
>>> @@ -136,8 +136,14 @@ cnd_timedwait(cnd_t *cond, mtx_t *mtx, const xtime *xt)
>>
>> I'm confused. The docs here [1] give a different prototype for this
>> function -- one without the xt argument. Is our implementation for
>> some pre-C11 spec?
>
> It's not without the xt argument... it's with that argument having a
> different (const struct timespec* restrict time_point) type.  It looks
> like mtx_timedlock (http://en.cppreference.com/w/c/thread/mtx_timedlock)
> has the same issue.
>
> As far as I can tell, C11 struct timespec
> (http://en.cppreference.com/w/c/chrono/timespec) is the same as Linux
> struct timespec.  POSIX
> (http://pubs.opengroup.org/onlinepubs/009695399/basedefs/time.h.html)
> allows it to have extra fields, but I don't think that should be a
> problem.  Maybe there's a conflict on Windows?  Maybe Jose knows?
>
>> [1] http://en.cppreference.com/w/c/thread/cnd_timedwait

No, that prototype comes from the original source code [1], so I don't 
know the background story behind it (ie, if it's because it was based on 
an ealier C11 draft, or due to crossplatform reasons.


AFAICT, there's no conflict on Windows.  However, MSVC doesn't define 
timespec, while MinGW (at least some versions) do.


In short, we could use "timespec" everywhere, relying on time.h 
definition on Linux, and defining our own struct timespec for Windows 
when not available.


That is, some like:

diff --git a/include/c11/threads.h b/include/c11/threads.h
index 45823df..c8b3819 100644
--- a/include/c11/threads.h
+++ b/include/c11/threads.h
@@ -41,11 +41,17 @@
  typedef void (*tss_dtor_t)(void*);
  typedef int (*thrd_start_t)(void*);

-struct xtime {
-    time_t sec;
-    long nsec;
+#if defined(_MSC_VER) || (defined(__MINGW__) && 
!defined(___TIMESPEC_DEFINED))
+
+struct timespec {
+    time_t tv_sec;
+    long tv_nsec;
  };
-typedef struct xtime xtime;
+
+#endif
+
+// FIXME: actually rename `xtime` with `struct timespec`, sec -> 
tv_sec, etc.
+#define xtime struct timespec


  /*-------------------- enumeration constants --------------------*/






Jose



[1] https://gist.github.com/yohhoy/2223710