JDK 9 RFR of JDK-8074977: Constructor.getAnnotatedParameterTypes returns wrong value

Remi Forax forax at univ-mlv.fr
Sat May 20 21:09:26 UTC 2017

Hi Joe,
we had the same issue with ASM, we solve it without trying to detect every corner cases but by just comparing the number of parameter from the descriptor and the number of parameter (type?) annotations,
if there are less annotations, we add fake annotations at the starts of the array [1].

I don't remember the exact details but i'm pretty sure that at some point in the past ecj (the eclipse compiler) was generating more than one reference if you had an anonymous class inside an anonymous class.

ASM reports a special fake annotation "Ljava/lang/Synthetic;" so users can see that this is a synthetic parameter but i don't think it's a good idea to do that in the reflection API, ASM is more low level.


[1] http://websvn.ow2.org/filedetails.php?repname=asm&path=%2Ftrunk%2Fasm%2Fsrc%2Forg%2Fobjectweb%2Fasm%2FClassReader.java, in method readParameterAnnotations(). 

----- Mail original -----
> De: "Peter Levart" <peter.levart at gmail.com>
> À: "joe darcy" <joe.darcy at oracle.com>, "core-libs-dev" <core-libs-dev at openjdk.java.net>
> Envoyé: Samedi 20 Mai 2017 20:00:25
> Objet: Re: JDK 9 RFR of JDK-8074977: Constructor.getAnnotatedParameterTypes returns wrong value

> Hi Joe,
> So enum classes, anonymous classes and local classes don't have a
> standard way of passing synthetic/implicit constructor parameters? Do
> various compilers do it differently than javac?
> It's unfortunate but if # of parameter annotations arrays is less than
> the # of parameters, Parameter.getAnnotations() may return wrong
> annotations or throw IndexOutOfBoundException for enums, anonymous and
> local classes. Can't we do anything for them? At least for code compiled
> by javac?
> For example, javac compiles enum classes so that they always prefix
> constructor source parameters with a pair of (String name, int ordinal,
> ...) and so do anonymous enum subclasses provided by enum constants
> (i.e. clazz.isAnonymousClass() && clazz.getSuperclass().isEnum())
> Non-static local classes are compiled so that constructor source
> parameters are prefixed with a single parameter (OuterClass
> outerInstance, ...), while any captured variables follow source parameters
> Static local classes are compiled so that constructor source parameters
> come 1st, followed by any captured variables.
> etc...
> Regards, Peter
> On 05/19/2017 11:31 PM, joe darcy wrote:
>> Hello,
>> Please review the webrev to fix
>>     JDK-8074977: Constructor.getAnnotatedParameterTypes returns wrong
>> value
>>     http://cr.openjdk.java.net/~darcy/8074977.3/
>> To condense a complicated situation, there are cases where the number
>> of parameters present for a constructor in source code and the number
>> of parameters present for that constructor in the class file differ.
>> One of those cases occurs for the constructor of a non-static member
>> class [1] where there is a leading parameter to accept the outer this
>> argument.
>> Bug JDK-8074977 reports on a situation where the type annotations on
>> constructor parameters are incorrectly reported. Essentially, an
>> off-by-one error is the cause since the annotation information is
>> stored with respect to the number of parameters present in the source
>> and an additional parameter is present at runtime.
>> An analogous situation exists for declaration annotations and
>> constructor parameters, declaration annotations being the traditional
>> flavor of annotations.
>> Type annotations and declaration annotations are read using different
>> APIs so require separate fixes to detect the additional parameter and
>> make the necessary adjustments in the returned information.
>> The regression tests cover both the type annotation reading API and
>> the two ways of reading declaration annotations on parameters, calling
>> getParameterAnnotations on the constructor or call getParameters on
>> the constructor and then calling getAnnotations on each parameter. The
>> getParameters API was added in JDK 8.
>> Static member and non-static member classes are used as test cases, as
>> are constructors with and without generic type information.
>> Thanks,
>> -Joe
>> [1]
>> https://blogs.oracle.com/darcy/nested,-inner,-member,-and-top-level-classes

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