RFR: 8313452: Improve Classfile API attributes handling safety [v2]

[ExE Boss]

On Wed, 6 Sep 2023 12:28:05 GMT, Adam Sotona <asotona at openjdk.org> wrote:

>> This PR improved Classfile API attributes handling safety by introduction of attribute stability indicator
>> and by extension of UnknownAttributesOption to more general AttributesProcessingOption.
>
> Adam Sotona has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 23 commits:
> 
>  - fixed javadoc wording
>  - HAZMAT renamed to UNSTABLE
>    no filtering on read
>    filtering on write only for bound attributes
>  - Merge branch 'master' into JDK-8313452-attributes-safety
>    
>    # Conflicts:
>    #	src/java.base/share/classes/jdk/internal/classfile/Classfile.java
>  - Merge branch 'JDK-8312491-snippets' into JDK-8313452-attributes-safety
>  - added notes to attributes
>  - fixing javadoc
>  - fixing javadoc
>  - fixing javadoc
>  - fixing javadoc
>  - removed extra lines
>  - ... and 13 more: https://git.openjdk.org/jdk/compare/744b3970...ce77e2ae

src/java.base/share/classes/jdk/internal/classfile/impl/AbstractDirectBuilder.java line 59:

> 57:         if (a instanceof UnboundAttribute ||
> 58:             5 - a.attributeMapper().attributeStability().ordinal()
> 59:                     > context.attributesProcessingOption().ordinal()) {

Maybe extract the `5 - a.attributeMapper().attributeStability().ordinal() > context.attributesProcessingOption().ordinal()` check into a helper method, as the current expression is too noisy:

import jdk.internal.classfile.AttributeMapper.AttributeStability;
import jdk.internal.classfile.Classfile.AttributesProcessingOption;

private static final int ATTRIBUTE_STABILITY_COUNT = AttributeStability.values().length;
public static boolean isAttributeAllowed(
	final AttributeStability stability,
	final AttributesProcessingOption processingOption
) {
	return ATTRIBUTE_STABILITY_COUNT - stability.ordinal() > processingOption.ordinal();
}


Also, the magic number should probably be replaced with a constant storing the value of `AttributeStability.values().length`.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/15101#discussion_r1317326262