RFR: 8253899: Make IsClassUnloadingEnabled signature match specification

[Vladimir Kempik]

On Fri, 2 Oct 2020 07:34:45 GMT, Vladimir Kempik <vkempik at openjdk.org> wrote:

>> Okay but look at the example that documentation gives:
>> 
>>> For example, if the jvmtiParamInfo returned by GetExtensionEvents indicates that there is a jint parameter, the event
>>> handler should be declared:
>>>         void JNICALL myHandler(jvmtiEnv* jvmti_env, jint myInt, ...)
>> 
>> The myInt is explicit, just as our "jboolean* enabled" is explicit. I think they key point is that the signature must
>> end with "..." which it does.
>> I don't see anything here that needs to be fixed.
>
>> Okay but look at the example that documentation gives:
>> 
>> > For example, if the jvmtiParamInfo returned by GetExtensionEvents indicates that there is a jint parameter, the event
>> > handler should be declared: ```
>> >     void JNICALL myHandler(jvmtiEnv* jvmti_env, jint myInt, ...)
>> > ```
>> 
>> The myInt is explicit, just as our "jboolean* enabled" is explicit. I think they key point is that the signature must
>> end with "..." which it does.
>> I don't see anything here that needs to be fixed.
> 
> Hello David. On majority of platforms this would be fine.
> 
> But on some platforms, variadic arguments and non variadic arguments are passed differently ( for example on
> macos-aarch64, variadic args are passed always on stack, non variadic on registers (and on stack for 9th+ arg) , that
> causes issues.  If you still see no issues here we can delay and make this changeset part of JEP-391.
> But since this changeset isn't much macos-aarch64 specific, I thought it would be good to integrate it separately from
> jep-391.
> Regards, Vladimir

> _Mailing list message from [David Holmes](mailto:david.holmes at oracle.com) on
> [hotspot-dev](mailto:hotspot-dev at openjdk.java.net):_
> Hi Vladimir,
> 
> On 2/10/2020 5:37 pm, Vladimir Kempik wrote:
> 
> > On Fri, 2 Oct 2020 07:27:17 GMT, David Holmes <dholmes at openjdk.org> wrote:
> > > Okay but look at the example that documentation gives:
> > > > For example, if the jvmtiParamInfo returned by GetExtensionEvents indicates that there is a jint parameter, the event
> > > > handler should be declared: ```
> > > > void JNICALL myHandler(jvmtiEnv* jvmti_env, jint myInt, ...)
> > > > ```
> > > 
> > > 
> > > The myInt is explicit, just as our "jboolean* enabled" is explicit. I think they key point is that the signature must
> > > end with "..." which it does.
> > > I don't see anything here that needs to be fixed.
> > 
> > 
> > Hello David. On majority of platforms this would be fine.
> > But on some platforms, variadic arguments and non variadic arguments are passed differently ( for example on
> > macos-aarch64, variadic args are passed always on stack, non variadic on registers (and on stack for 9th+ arg) , that
> > causes issues.
> 
> Okay - I see the potential for a problme here but ...
> 
> > If you still see no issues here we can delay and make this changeset part of JEP-391.
> > But since this changeset isn't much macos-aarch64 specific, I thought it would be good to integrate it separately from
> > jep-391.
> 
> ... this change actually goes against the example in the spec, so if you
> make this change it indicates the spec needs to be updated too.
> 
> Cheers,
> David
> -----

Hello David

I really believe the problem is in document here ( in examples)
first, the doc clearly specify the type

typedef jvmtiError (JNICALL *jvmtiExtensionFunction)
    (jvmtiEnv* jvmti_env,
      ...);

then in examples it declares the function not matching this spec.

Is it a good idea to update the docs in a separate bug ?

Thanks, Vladimir

-------------

PR: https://git.openjdk.java.net/jdk/pull/466