RFR(XXS): 8242485: Null _file checking in fileStream::flush()

[Liu, Xin]

Hi, Dong, 

LGTM. (I am not reviewer).  
I just realize that fflush accepts NULL, but "If the stream argument is NULL, fflush() flushes all open output streams."
Although it doesn't cause runtime error, it may cause unexpected IO latency. 

Thanks,
--lx

On 4/10/20, 5:36 AM, "hotspot-dev on behalf of Denghui Dong" <hotspot-dev-bounces at openjdk.java.net on behalf of denghui.ddh at alibaba-inc.com> wrote:

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    Hi team,
    
    Could you please review this small patch?
    
    JBS: https://bugs.openjdk.java.net/browse/JDK-8242485
    webrev: http://cr.openjdk.java.net/~ddong/8242485/webrev.00/
    
    I found the method "fileStream::flush()" lacks null check before fflush  which will cause
    all open output streams are flushed by fflush() if _file is NULL.
    
    Thanks,
    Denghui Dong