RFR: 8150103: Convert TraceClassPaths to Unified Logging

[Ioi Lam]

Hi Max,

I think it's OK to always print to the logging stream. For the handling 
of PrintSharedArchiveAndExit, I would suggest that in arguments.cpp: if 
PrintSharedArchiveAndExit is enabled, force -Xlog:classpath if it's not 
yet enabled.

So the meaning of PrintSharedArchiveAndExit becomes:

If -Xlog:classpath has not been explicitly specified in the 
command-line, then we enable -Xlog:classpath to stdout.

Thanks
- Ioi

On 2/18/16 8:36 AM, Max Ockner wrote:
> Hi David,
>
> I agree with what you have said. Allowing trace_class_path to print to 
> tty yields a lot of junk output even when classpath logging is not 
> turned on. We now will only want to print to the classpath info 
> stream, so given the current logging API does it make sense to 
> hard-code this stream into trace_class_path and remove the stream 
> argument? Why should we keep the 3 argument version if it is always 
> being used with the same stream argument? Do we expect it to someday 
> use additional streams?
>
> Thanks,
> Max
>
> On 2/18/2016 7:28 AM, David Holmes wrote:
>> Hi Max,
>>
>> This conversion is not straight-forward, and not complete.
>>
>> On 18/02/2016 8:19 AM, Max Ockner wrote:
>>> Hello everyone,
>>> Please review this conversion of TraceClassPaths to UL.
>>>
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8150103
>>> Webrev: http://cr.openjdk.java.net/~mockner/classpath.03/
>>
>> src/share/vm/classfile/classLoader.cpp
>>
>> This call:
>>
>>  477     trace_class_path(tty, "[Bootstrap loader class path=", 
>> sys_class_path);
>>
>> shouldn't be passing tty but should be the outputstream for the 
>> "info" log.
>>
>> ---
>>
>> src/share/vm/runtime/arguments.cpp
>>
>> Same here:
>>
>>   if (!PrintSharedArchiveAndExit) {
>>     ClassLoader::trace_class_path(tty, "[classpath: ", 
>> _java_class_path->value());
>>   }
>>
>> ---
>>
>> src/share/vm/classfile/sharedPathsMiscInfo.hpp
>>
>> You didn't modify this file but you need to change the 2-arg 
>> trace_class_path() to not use the tty.
>>
>> This conversion seems a bit problematic to me. trace_class_path was 
>> enabled/disabled via TraceClassPaths, but it could write to different 
>> output streams. With UL you would always want it to write to the 
>> single UL related stream - which means the API really needs to 
>> change, and the extraction of the correct log stream can then be 
>> internalized. But there may be some compatibility issues in doing 
>> that for the place(s) where it may not be writing to tty.
>>
>> I don't see a simple conversion process here. I think all 
>> trace_class_path calls should be the two-arg forms with no stream 
>> arg, and that version then inlines the current 3-arg version but 
>> always writes to the info log stream. But then you also have 
>> print_path which wraps a call to trace_class_path ... to be honest I 
>> don't see what purpose print_path serves, it just seems to be 
>> complicating things.
>>
>> David
>> ----
>>
>>
>>> Summary:  TraceClassPaths flag has been reimplemented using the
>>> classpath tag with Info level.  TraceClassPaths has been added to the
>>> logging alias table.
>>> There is some related output that was never guarded by "if
>>> (TraceClassPaths)", so it has not been included in this conversion.
>>> Testing: jtreg runtime tests. Added basic test case at
>>> test/runtime/logging/ClassPathTest.java
>>>
>>> Thanks,
>>> Max
>