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

[David Holmes]

Hi Denghui,

On 12/04/2020 2:41 pm, Denghui Dong wrote:
> Hi David,
> 
> Thanks for the comments
> new webrev: http://cr.openjdk.java.net/~ddong/8242485/webrev.02
> 
> when _file is NULL:
> - fileStream::read return 0
> - fileStream::readln return NULL
> - fileStream::eof return -1 (like 
> fileStream::fileSize, not sure if appropriate, feof returns nonzero if target file is end)

That is all great - thanks!

Unfortunately the more I look at this code the more problems I see with 
it. :( We have:

void fileStream::write(const char* s, size_t len) {
   if (_file != NULL)  {
     // Make an unused local variable to avoid warning from gcc compiler.
     size_t count = fwrite(s, 1, len, _file);
   }
   update_position(s, len);
}

but the update_position should be inside the if-statement - no need to 
see a new webrev for that.

We should also be watching for errors from fwrite - but that in itself 
just opens up a can-of-worms with regard to error handling in general 
with this class, so that can be left as-is.

Thanks,
David
-----

> Testing: tier1
> 
> Cheers,
> Denghui Dong
> 
>     ------------------------------------------------------------------
>     From:David Holmes <david.holmes at oracle.com>
>     Send Time:2020年4月12日(星期日) 10:40
>     To:董登辉(卓昂) <denghui.ddh at alibaba-inc.com>; hotspot-dev
>     <hotspot-dev at openjdk.java.net>; hotspot-runtime-dev at openjdk.java.net
>     <hotspot-runtime-dev at openjdk.java.net>; Yasumasa Suenaga
>     <suenaga at oss.nttdata.com>; "Liu, Xin" <xxinliu at amazon.com>
>     Subject:Re: RFR(XXS): 8242485: Null _file checking in
>     fileStream::flush()
> 
>     Hi,
> 
>     On 12/04/2020 1:52 am, Denghui Dong wrote:
>      > Hi,
>      > Thank you for the review and point out other methods need to check _file.
>      > In addition to "fileStream::flush", I found there are still four methods need to check _file in fileStream: read, readln, eof, rewind.
>      > but those methods will crash if _file is NULL, and I didn't find any caller of them(Maybe I am wrong),
>      > so I think it's more appropriate to add assert check to those methods.
> 
>     Assertions are really only appropriate if they will be exercised by
>     tests - the intent being that tests will expose any cases where the
>     assertion fails.
> 
>     Also it doesn't make sense to me to have assertions in most places but a
> 
>     true NULL check in others - that suggests we expect some methods to be
>     called when _file is NULL, but others not. I'd prefer just to see the
>     missing NULL checks added, rather than using assertions.
> 
>     Thanks,
>     David
> 
>      > Webrev: http://cr.openjdk.java.net/~ddong/8242485/webrev.01/
>      >
>      > Could you review it again, and sponsor it if everything is okay?
>      >
>      > Testing: teir1
>      > ==============================
>      > Test summary
>      > ==============================
>      >     TEST                                              TOTAL  PASS  FAIL ERROR
>      >     jtreg:test/hotspot/jtreg:tier1                     1516  1516     0     0
>      >     jtreg:test/jdk:tier1                               1904  1904     0     0
>      >  >> jtreg:test/langtools:tier1                         4031  4029     2     0 <<
>      >     jtreg:test/nashorn:tier1                              0     0     0     0
>      >     jtreg:test/jaxp:tier1                                 0     0     0     0
>      > ==============================
>      > There are two unrelated test failures in
>      > langtools: jdk/javadoc/tool/CheckResourceKeys.java  and tools/javac/processing/model/TestSymtabItems.java
>      >
>      >
>      >
>      >     ------------------------------------------------------------------
>      >     From:Yasumasa Suenaga <suenaga at oss.nttdata.com>
>      >     Send Time:2020年4月11日(星期六) 09:22
>      >     To:董登辉(卓昂) <denghui.ddh at alibaba-inc.com>; hotspot-dev
>      >     <hotspot-dev at openjdk.java.net>; hotspot-runtime-dev at openjdk.java.net
>      >     <hotspot-runtime-dev at openjdk.java.net>
>      >     Subject:Re: RFR(XXS): 8242485: Null _file checking in
>      >     fileStream::flush()
>      >
>      >     Hi Denghui,
>      >
>      >     null check lacks in other place too.
>      >     Can you fix it?
>      >
>      >         http://hg.openjdk.java.net/jdk/jdk/file/97d5d0cd1085/src/hotspot/share/utilities/ostream.cpp#l554
>      >
>      >
>      >     Thanks,
>      >
>      >     Yasumasa
>      >
>      >
>      >     On 2020/04/10 21:34, Denghui Dong wrote:
>      >      > 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
>      >      >
>      > 
>