RFR(S): 8198608: Improvements to command-line flags printing

[Schmidt, Lutz]

Hi David, 

it would be great if you could sponsor this change. I was able to successfully test on darwinintel64, linuxs390x, linuxppc64, and linuxx86_64. Our AIX systems are not playing nice with me at the moment (no issues with the change, just general misbehavior).

I have modified line 551 according to your suggestion (and line 519 as well). Webrev updated in-place.

So let's hope for a second review over the weekend. 

Regards,
Lutz


On 02.03.18, 02:19, "David Holmes" <david.holmes at oracle.com> wrote:

    On 1/03/2018 11:25 PM, Schmidt, Lutz wrote:
    > Hi David,
    > thank you for looking at this. You are right, the comment is a useless leftover -> removed in if and else branch.
    
    Looks fine. Just need a second reviewer. Do you need a sponsor to test 
    on additional platforms? Otherwise what platforms have you tested?
    
    > With the "\n" handling, I believe we are on the safe side. If a newline character is detected in the parameter string, it is replaced by a st->cr() call. That call does the expected on any platform, I would hope. Flag::print_as_flag() (not in the scope of the change) uses a similar handling.
    > 
    > The newlines are contained in string literals in C code (e.g. default values for parameters) or stem from ccstrlist concatenations. That is all under VM control. So I do not see a risk here. You can try yourself on any platform with the -XX:DisableIntrinsic=test1 parameter multiple times.
    > 
    > If a user manages to specify a parameter string with platform (windows) specific line terminators and hopes for correct (\n-like) handling, he or she will be disappointed. I would assume the PrintFlags formatting isn't the only place that's impacted.
    
    Sorry I mistakenly thought you had modified the newline handling, when 
    you hadn't. If there is an issue it would be preexisting. I was 
    wondering how you would get a multi-line ccstr value. If you entered it 
    on the command-line e.g:
    
    java -XX:OnError="Line 1
    Line2"
    
    then I would expect to find the platform line separator within the 
    string. In testing this with the existing PrintFlagsFinal Linux does:
    
    ccstrlist OnError                                  = Line 1
           OnError                             += Line 2 
                   {product} {command line}
    
    but testing on Windows is a problem. The regular cmd shell can't take 
    multi-line arguments. If you use the ^ escape trick it actually strips 
    the newline and passes the arg as one line. So I guess the issue is 
    somewhat moot. :)
    
    
    One further nit:
    
      551           st->print("%s", "+=");
    
    should just be:
    
      551           st->print("+=");
    
    Thanks,
    David
    
    > I have updated the webrev in-place with the comments removed.
    > 
    > Thanks again, Lutz
    > 
    > 
    > On 28.02.18, 23:26, "David Holmes" <david.holmes at oracle.com> wrote:
    > 
    >      Hi Lutz,
    >      
    >      On 24/02/2018 2:48 AM, Schmidt, Lutz wrote:
    >      > Dear all,
    >      >
    >      > may I please request reviews for this small enhancement:
    >      >
    >      > Bug:     https://bugs.openjdk.java.net/browse/JDK-8198608
    >      > Webrev:  http://cr.openjdk.java.net/~lucy/webrevs/8198608.00/
    >      >
    >      > The code in Flag::print_on() so far wasn’t very easy to understand. Changing the layout of what was printed required some deep thinking. I hope that, with my changes, future modifications will be easier.
    >      >
    >      > The before/after output of -XX:+PrintFlagsFinal is identical, except for those argument names which are longer than expected. In that case, the new version prints one space less, which is by intention.
    >      
    >      This all seems okay - and easier to modify further if needed.
    >      
    >      Two minor comments:
    >      
    >        576     // Flag::print_on(...) redesign (!print_ranges)
    >      
    >      Isn't this the print_ranges case? But in any case not sure a comment
    >      with "redesign" in it is that meaningful given you can't see the old design.
    >      
    >      Does the ccstr newline handling work on all platforms (ie Windows) - I'm
    >      never sure when it suffices to check for '\n' and when we have to check
    >      for the platform specific line terminators.
    >      
    >      Thanks,
    >      David
    >      
    >      > Thank you!
    >      > Lutz
    >      >
    >      >
    >      >
    >      > Dr. Lutz Schmidt | SAP JVM | PI  SAP CP Core | T: +49 (6227) 7-42834
    >      >
    >      
    >