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

[Lindenmaier, Goetz]

Hi Lutz, 

thanks for this change, using st->fill_to() here is very helpful.
I played a bit with it, works fine. Reviewed.

Best regards,
  Goetz.

> -----Original Message-----
> From: hotspot-runtime-dev [mailto:hotspot-runtime-dev-
> bounces at openjdk.java.net] On Behalf Of Schmidt, Lutz
> Sent: Freitag, 2. März 2018 16:05
> To: David Holmes <david.holmes at oracle.com>; hotspot-runtime-
> dev at openjdk.java.net
> Subject: [CAUTION] Re: RFR(S): 8198608: Improvements to command-line
> flags printing
> 
> 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
>     >      >
>     >
>     >
>