On Thu, 6 Apr 2023 20:47:10 GMT, Chen Liang <li...@openjdk.org> wrote:
>> As John Rose has pointed out in this issue, the current j.l.r.Proxy based >> implementation of MethodHandleProxies.asInterface has a few issues: >> 1. Exposes too much information via Proxy supertype (and WrapperInstance >> interface) >> 2. Does not allow future expansion to support SAM[^1] abstract classes >> 3. Slow (in fact, very slow) >> >> This patch addresses all 3 problems: >> 1. It implements proxies with one hidden class for each requested interface >> and replaced WrapperInstance inheritance with a check to the class data. >> This can avoid unexpected passing of `instanceof`, and avoids the nasty >> problem of exporting a JDK interface to a dynamic module to ensure access. >> 2. This patch obtains already generated classes from a ClassValue by the >> requested interface type; the ClassValue can later be updated to compute >> implementation generation for abstract classes as well. >> 3. This patch's generated hidden classes has call performance on par with >> those of lambda expressions; the creation performance is slightly less than >> that of LambdaMetafactory: >> https://jmh.morethan.io/?gist=fcb946d83ee4ac7386901795ca49b224 >> >> Additionally, an obsolete `ProxyForMethodHandle` test was removed, for it's >> no longer applicable. Tests in `jdk/java/lang/invoke` and >> `jdk/java/lang/reflect` pass. >> >> [^1]: single abstract method > > Chen Liang has updated the pull request incrementally with one additional > commit since the last revision: > > Require an original lookup in constructor arguments to prevent unintended > instantiation src/java.base/share/classes/java/lang/invoke/MethodHandleProxies.java line 317: > 315: cob.aload(1); > 316: cob.invokevirtual(CD_MethodHandles_Lookup, > "lookupClass", MTD_Class); > 317: cob.constantInstruction(proxyDesc); This probably can’t use `LDC` of `CONSTANT_Class`, as that can’t refer to hidden classes: Suggestion: cob.aload(0); cob.invokevirtual(CD_Object, "getClass", MTD_Class); -------------------------------------------------------------------------------- Having a helper constant bootstrap of the following form would allow to obtain the current class using a dynamic constant: public static final Class<?> lookupClass( final MethodHandles.Lookup lookup, final String name, @SuppressWarnings("rawtypes") // needed to allow `Class.class` final Class<? extends Class> type ) { requireNonNull(lookup); requireNonNull(type); if (type != Class.class) { throw new IllegalArgumentException(); } return lookup.lookupClass(); } ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/13197#discussion_r1160636661
