RFR: 8256008: UL does not report anything if disk writing fails [v2]

[Yasumasa Suenaga]

On Tue, 1 Dec 2020 15:53:39 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Yasumasa Suenaga has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:
>> 
>>  - refactoring
>>  - Merge branch 'master' into JDK-8256008
>>  - Fix typo
>>  - 8256008: UL does not report anything if disk writing fails
>
> Hi Yasumasa,
> 
> this is good, but some nits remain, see below.
> 
> Cheers, Thomas

@tstuefe Thanks for your review! I updated PR. Could you review again?

> src/hotspot/share/logging/logFileStreamOutput.cpp line 109:
> 
>> 107: {                                                             \
>> 108:   int result = op;                                            \
>> 109:   if (result <= 0) {                                          \
> 
> May be not completely correct for all values of op:
> - fprintf returns a negative value (0 is valid if length to write was 0). I did not check jio_fprintf but I assume the return semantics are the same?
> - write_decorations returns 0 if it did not write any decorations, which is valid

`jio_fprintf()` would call `vfprintf()`, so I concerned in case that `vfprintf()` cannot write enough. Callers of `jio_fprintf()` other than `write_decorations()` would write 1 byte at least.
However `write_decorations()` might not write any chars, and also `vfprintf()` in glibc does not seem to return halfway value. So I updated condition to `< 0`.

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PR: https://git.openjdk.java.net/jdk/pull/1106