On Tue, 25 Oct 2022 17:34:15 GMT, Ioi Lam <ik...@openjdk.org> wrote:
>> I've added a `java.lang.invoke.MethodHandle.TRACE_CALLSITE` property to show
>> how invokedynamic call sites are resolved.
>>
>> For example:
>>
>>
>> public class StrConcat {
>> static String hello = "Hello";
>> static String world = "World";
>> public static void main(String args[]) {
>> System.out.println(hello + world);
>> System.out.println(hello + "World");
>> }
>> }
>>
>> $ java -Djava.lang.invoke.MethodHandle.TRACE_CALLSITE=true -cp . StrConcat
>> ======== CallSite: StrConcat.main(StrConcat.java:5)
>> BSM =
>> java.base/java.lang.invoke.StringConcatFactory.makeConcatWithConstants(StringConcatFactory.java:354)
>> target class = java.lang.invoke.BoundMethodHandle$Species_L
>> target = (String,String)String : BMH.reinvoke=Lambda(a0:L/SpeciesData[L =>
>> Species_L],a1:L,a2:L)=>{
>> t3:L=Species_L.argL0(a0:L);
>> t4:L=MethodHandle.invokeBasic(t3:L,a1:L,a2:L);t4:L}
>> & BMH=[
>> 0: MethodHandle = {(Object,Object)String :
>> DMH.invokeStatic=Lambda(a0:L,a1:L,a2:L)=>{
>> t3:L=DirectMethodHandle.internalMemberName(a0:L);
>> t4:L=MethodHandle.linkToStatic(a1:L,a2:L,t3:L);t4:L}
>> &
>> DMH.MN=java.lang.StringConcatHelper.simpleConcat(Object,Object)String/invokeStatic
>> }
>> ]
>> HelloWorld
>> ======== CallSite: StrConcat.main(StrConcat.java:6)
>> BSM =
>> java.base/java.lang.invoke.StringConcatFactory.makeConcatWithConstants(StringConcatFactory.java:354)
>> target class = java.lang.invoke.BoundMethodHandle$Species_LL
>> target = (String)String : invoke=Lambda(a0:L/SpeciesData[LL =>
>> BoundMethodHandle$Species_LL],a1:L)=>{
>> t2:L=BoundMethodHandle$Species_LL.argL1(a0:L);
>> t3:L=BoundMethodHandle$Species_LL.argL0(a0:L);
>> t4:L=MethodHandle.invokeBasic(t3:L,a1:L,t2:L);t4:L}
>> & BMH=[
>> 0: MethodHandle = {(Object,Object)String :
>> DMH.invokeStatic=Lambda(a0:L,a1:L,a2:L)=>{
>> t3:L=DirectMethodHandle.internalMemberName(a0:L);
>> t4:L=MethodHandle.linkToStatic(a1:L,a2:L,t3:L);t4:L}
>> &
>> DMH.MN=java.lang.StringConcatHelper.simpleConcat(Object,Object)String/invokeStatic
>> }
>> 1: ( World )
>> ]
>> HelloWorld
>>
>>
>> More complex examples are in the JBS bug report
>> - https://bugs.openjdk.org/secure/attachment/101170/eclipse-ide-log.txt
>> - https://bugs.openjdk.org/secure/attachment/101168/lambda-expression.txt
>> -
>> https://bugs.openjdk.org/secure/attachment/101174/pattern-matching-switch.txt
>> - https://bugs.openjdk.org/secure/attachment/101169/str-concat.txt
>
> Ioi Lam has updated the pull request incrementally with one additional commit
> since the last revision:
>
> @JornVernee comments
The changes look good, but I have some more comments.
src/java.base/share/classes/java/lang/invoke/MethodHandleNatives.java line 329:
> 327: return null;
> 328: }
> 329: });
Not sure about this condition. It seems like `callerInfo[0] == callerName` will
always be true at first, and then it gets overwritten by the stack trace
element toString, so in effect it only picks up the first
non-MethodHandleNatives caller? I think it could be clearer to use `filter` +
`findFirst` to get the caller's `StackFrame` (that has the additional benefit
of short-circuiting), and then convert to a String from there.
Also, please move the code that gets the caller info out-of-line to a helper
method, since it's quite wordy.
-------------
PR: https://git.openjdk.org/jdk/pull/10842
