Re: [Sablevm-developer] java.lang.Thread.yield()

[Chris P. <chr...@ma...>]

Hi Etienne,

Prof. Etienne M. Gagnon wrote:

>On Wed, Feb 19, 2003 at 08:36:58PM -0500, Chris Pickett wrote:
>  
>
>>I don't know what JNI_OK is defined to be (I couldn't find it with 
>>grep), but if it's zero then that's:
>>
>>if (sched_yield() != JNI_OK)
>>   _svmf_error_InternalError (env);
>>    
>>
>
>No!!!!  JNI_OK is used by _svmf_* functions to indicate success.  You
>should never make any relation between the actual integer value JNI_OK
>is defined as, and the accidental value it matches in another context!
>  
>
>If I decided to change JNI_OK to be defined as 36, the code above
>would start misbehaving (assuming JNI_OK was originally defined as
>zero).
>
Okay.  Where is JNI_OK defined?

>
>Also, you should *ALWAYS* check return values of non-void functions.
>I had not double-checked if sched_yield returned a value.  I guess I
>should never trust submitted code and review thoroughly every line of
>code and the documentation of every called library function...
>  
>
Well, actually, I realized last night about checking the error status, 
after I emailed you to say that I would send a patch today, but then 
today you had already committed the code.  Then I got caught up in 
making scripts, and didn't get around to telling you yet.

sched_yield() returns 0 if there was no problem, or -1 if there was an 
error.

sched_yield() is not necessarily posix compliant, so perhaps you'd 
better use pthread_yield() ... pthread_yield() doesn't return a value 
ever either, so just replace sched_yield() with pthread_yield() and 
forget about the error check.

sched_yield() is in sched.h which is in the GNU C library, whereas 
pthread_yield() is in pthreads.  The only reason I used sched_yield() 
was because that's what you and Clark and I talked about.

Sorry for not letting you know earlier and not checking the code I sent 
you.  Transgression #1.

Chris