RFR: 8035648: Don't use Handle in java_lang_String::print

[Stefan Karlsson]

On 2014-02-24 13:11, David Holmes wrote:
> Stefan,
>
> On 24/02/2014 7:44 PM, Stefan Karlsson wrote:
>> Hi all,
>>
>> Please, review this change to let java_lang_String::print take a raw
>> String oop instead of a Handle to a String oop. This change makes
>> java_lang_String::print callable from code that has no HandleMark setup.
>
> I don't think you can do that. The printing code can encounter a 
> safepoint and block thus allowing a raw oop to be exposed over a 
> potential GC point.

If that's the case, then the code was already buggy before my change:

1) Before the patch the first thing we did was to convert the Handle to 
a raw oop. IMHO, there's no difference in safepoint safeness here.
void java_lang_String::print(Handle java_string, outputStream* st) {
   oop          obj    = java_string();

2) the 'value' object would also be susceptible to this kind of bug:
     for (int index = 0; index < length; index++) {
       st->print("%c", value->char_at(index + offset));
     }

Do you know of an implementation of outputStream that allows us to block 
for a safepoint? If not, would you be fine with the change if I add a 
No_Safepoint_Verifier?

thanks,
StefanK

>
>
> David
>
>> E.g. when calling from a debugger.
>>
>> Webrev:
>> http://cr.openjdk.java.net/~stefank/8035648/webrev.00/
>>
>> RFE:
>> https://bugs.openjdk.java.net/browse/JDK-8035648
>>
>> thanks,
>> StefanK