1 6829189: Java programming with JSR 292 needs language support

        2 6754038: writing libraries in Java for non-Java languages requires method handle invocation

        3 Summary: javac recognizes implicit methods assigned by JVM to MethodHandle and InvokeDynamic

        4 

        5 javac needs to support library development for non-Java langauges

        6 

        7 Language changes are documented in http://wikis.sun.com/display/mlvm/ProjectCoinProposal

        8 

        9 http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6754038

       10 

       11 Features:

       12 - the method java.dyn.MethodHandle.<T>invoke(AAA)T exists, even if not explicitly found

       13 - the static method java.dyn.InvokeDynamic.<T>zzz(AAA)T always exists, even if not explicitly found

       14 - the return type parameter <T> may be a primitive type or void

       15 - the return type parameter <T> may be omitted and defaults to Object

       16 - the signature of the implicit method is obtained by erasing actual argument types

       17 - null arguments are treated as of type java.lang.Void (which can only be a null reference)

       18 - no implicit conversions are performed on these calls; use a cast if you want conversion

       19 

       20 Discussion:

       21 See, for example, April-May 2009 discussions like the following:

       22   http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001617.html

       23   http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001418.html

       24 

       25 Examples from the unit test:

       26     void test(MethodHandle mh) {

       27         mh.invoke("world", 123);

       28         // previous line generates invokevirtual MethodHandle.invoke(String,int)Object

       29         InvokeDynamic.greet("hello", "world", 123);

       30         // previous line generates invokedynamic greet(Object,String,int)Object

       31     }

       32 

       33 Note that actual argument types can be overridden by casts, as in:

       34   mh.invoke((Object)"foo", (Integer)123)

       35   // previous line generates invokevirtual MethodHandle.invoke(Object,Integer)Object

       36 

       37 The return type defaults to Object, unless specified by a type argument.

       38 

       39 The syntax for return type specification is:

       40   mh.<R>invoke(aaa)  // generates signature (AAA)R

       41   mh.<String>invoke("foo", 123)  // signature is (String,int)String

       42   mh.<void>invoke("foo", 123)  // signature is (String,int)void

       43 

       44 The syntax for the receiverless formulation of invokedynamic is:

       45   InvokeDynamic.<R>zzz(obj,aaa)  // generates signature (Object,AAA)R

       46   InvokeDynamic.zzz(AAA)  // return type is Object by default

       47   InvokeDynamic.greet((Object)"hello", "world", 123)

       48   // previous line generates invokedynamic greet(Object,String,int)Object

       49   InvokeDynamic.<void>greet("hello", "world", 123)

       50   // previous line generates invokedynamic greet(Object,String,int)void

       51   // or (in a later JVM version) invokedynamic greet(String,String,int)void

       52 

       53 Notes & Status:

       54 - The syntax for invokedynamic is receiverless; the signature describes all stacked args.

       55 - The instruction uses a new code point (186) and takes a NameAndType reference, plus two zero bytes.

       56 - The flag -XDinvokedynamic also enables the new instruction, without otherwise changing the target.

       57 

       58 Authors:

       59 - John Rose (Sun)

       60 

       61 Tests:

       62 - unit tests test/tools/javac/meth/*

       63 

       64 Incremental testing:

       65 

       66 ---- Using the Command Line ----

       67 

       68 This does not require a full JDK build.

       69 

       70 $ cd .../langtools

       71 $ hg qpush meth.patch

       72 $ (cd make; make)

       73 

       74 $ mkdir ./dist/cp1

       75 $ ./dist/bin/javac -d dist/cp1 -target 7 test/tools/javac/meth/Invoke{Dyn,MH}.java

       76 $ ./dist/bin/javap -c -classpath dist/cp1 meth.Invoke{Dyn,MH}  # observe call sites

       77 

       78 (Note:  Your $PATH may need to include a $JAVA_HOME for Java 6.)

       79 

       80 ---- Using NetBeans ----

       81 

       82 (Assuming a link farm folder at ~/env/.)

       83 $ ln -s <some copy of jtreg> ~/env/JTREG_HOME

       84 $ ln -s <some java6 JRE> ~/env/JAVA6_HOME

       85 $ ln -s <some java6 JRE> ~/env/TARGET_JAVA_HOME

       86 $ ln -s <langtools dir> ~/env/LANGTOOLS

       87 

       88 Also, make sure your NetBeans is running Java 6 not Java 5.

       89 $ mkdir ~/.HOME/.netbeans/6.5/etc

       90 $ echo >> ~/.HOME/.netbeans/6.5/etc/netbeans.conf \

       91     "netbeans_jdkhome = $HOME/env/JAVA6_HOME

       92 

       93 Configure the OpenJDK build file properties:

       94 $ echo >> ~/.openjdk/build.properties    boot.java.home = ~/env/JAVA_HOME

       95 $ echo >> ~/.openjdk/build.properties    target.java.home = /Users/jrose/env/TARGET_JAVA_HOME

       96 $ echo >> ~/.openjdk/build.properties    jtreg.home = /Users/jrose/env/JTREG_HOME

       97 $ mkdir ~/env/LANGTOOLS/dist/cp0

       98 

       99 Right-click on the "langtools" project in NetBeans Project window, get 'select-tool'.

      100 Actually, the resulting config file changes like this:

      101 $ echo >> ~/env/LANGTOOLS/make/netbeans/langtools/nbproject/private/langtools.properties \

      102     javac.args = -d ~/env/LANGTOOLS/dist/cp0 -XDinvokedynamic ~/env/LANGTOOLS/test/tools/javac/meth/InvokeDyn.java