RFR(S) 8134898: Small fixes found during JVMCI work

[Bertrand Delsart]

On 02/09/2015 06:19, Vladimir Kozlov wrote:
>  > To resolve the incompatibility, you can simply remove
>  > CHECK_UNHANDLED_OOPS around the field in Thread, and put it under
>  > #ifndef PRODUCT.
>
> Wonderful! :) I thought it requires #ifdef CHECK_UNHANDLED_OOPS.
>
> Please, look on new changes:
>
> http://cr.openjdk.java.net/~kvn/8134898/webrev.01/

Looks good.

Small suggestion (feel free to ignore it). Might be even better to do:

    // Support for Unhandled Oop detection
-#ifdef CHECK_UNHANDLED_OOPS
+#if defined(CHECK_UNHANDLED_OOPS) || defined(ASSERT)
   private:
    UnhandledOops* _unhandled_oops;
+#endif
+#ifdef CHECK_UNHANDLED_OOPS
   public:
    UnhandledOops* unhandled_oops() { return _unhandled_oops; }
    // Mark oop safe for gc.  It may be stack allocated but won't move.

This version:
- does not prevent someone from building a PRODUCT VM with 
CHECK_HANDLED_OOPS if needed
- ensures someone does not call unhandled_oops() in debug VMs when 
CHECK_UNHANDLED_OOPS is not defined

Bertrand (not a Reviewer).

>
> Thanks,
> Vladimir
>
> On 9/1/15 8:55 PM, Coleen Phillimore wrote:
>>
>>
>> On 9/1/15 7:59 PM, Vladimir Kozlov wrote:
>>> http://cr.openjdk.java.net/~kvn/8134898/webrev/
>>> https://bugs.openjdk.java.net/browse/JDK-8134898
>>>
>>> During review of JVMCI changes we were asked to push not related small
>>> changes separately.
>>>
>>> Removed jre/ from jdk paths in makefiles since jdk9 does not have it
>>> anymore.
>>> Solaris vm.make and buildtree.make missed changes other unix platforms
>>> have.
>>> Fix type in doc.
>>> Added -DCHECK_UNHANDLED_OOPS to debug build. I very strongly want to
>>> do that.
>> Adding -DCHECK_UNHANDLED_OOPS to the debug build adds a level of
>> indirection to the oops that are somewhat annoying during debugging:
>>
>> eg.
>>
>> 692    void java_lang_Class::set_component_mirror(oop java_class, oop
>> comp_mirror) {
>> 693      assert(_component_mirror_offset != 0, "must be set");
>> 694        java_class->obj_field_put(_component_mirror_offset,
>> comp_mirror);
>> 695      }
>>
>> (gdb) print java_class
>> $7 = {_o = 0x8cb003b8}
>> (gdb) print java_mirror
>> No symbol "java_mirror" in current context.
>> (gdb) print comp_mirror
>> $8 = {_o = 0x8cb001b0}
>> (gdb) call hsfind(java_class._o)
>> warning: Using non-standard conversion to match function hsfind to
>> supplied arguments
>>
>> "Executing hsfind"
>> 0x000000008cb003b8 is an oop
>> java.lang.Class
>>   - klass: 'java/lang/Class'
>>   - ---- fields (total size 13 words):
>> ...
>>
>>
>> vs.
>>
>> 693      assert(_component_mirror_offset != 0, "must be set");
>> (gdb) print java_class
>> $1 = (oop) 0x8cb003b8
>> (gdb) print comp_mirror
>> $2 = (oop) 0x8cb001b0
>> (gdb) print hsfind(java_class)
>> warning: Using non-standard conversion to match function hsfind to
>> supplied arguments
>>
>> "Executing hsfind"
>> 0x000000008cb003b8 is an oop
>> java.lang.Class
>>   - klass: 'java/lang/Class'
>>   - ---- fields (total size 13 words):
>> ...
>>
>>
>> The GC people deal with far more 'oop' objects in their debugging, which
>> is why they asked me originally not to enable CHECK_UNHANDLED_OOPS in
>> the debug build.
>>
>> To resolve the incompatibility, you can simply remove
>> CHECK_UNHANDLED_OOPS around the field in Thread, and put it under
>> #ifndef PRODUCT.
>>
>> Coleen
>>> It is the only incompatibility in memory layout between fastdebug and
>>> debug VM. We maintained such compatibility for long time and it was
>>> broken with 7195622 changes.
>>> For AOT project it is very important to keep compatibility because we
>>> use fastdebug VM for JAOTC tool to compile aot code and we want to be
>>> able use debug VM to debug execution of aot code.
>>> Note, using debug VM with JAOTC will take 5-10 times longer to compile.
>>>
>>> Thanks,
>>> Vladimir
>>


-- 
Bertrand Delsart,                     Grenoble Engineering Center
Oracle,         180 av. de l'Europe,          ZIRST de Montbonnot
38330 Montbonnot Saint Martin,                             FRANCE
bertrand.delsart at oracle.com             Phone : +33 4 76 18 81 23

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