[build] Add support for JDK 21 (#1287)

Context: 5bb0d24
Context: 4273e5c
Context: 0355acf
Context: dotnet/android#9651
Does dotnet/android build with JDK-21? We don't know! But in order
to answer that question, dotnet/java-interop needs to be able to
build under JDK-21; a'la 5bb0d24:
1. [Install JDK-21][0]
2. Run `dotnet build -t:Prepare`, overriding `$(JdksRoot)` to refer
to the JDK-21 installation directory:
dotnet build -t:Prepare Java.Interop.sln -p:JdksRoot=/Library/Java/JavaVirtualMachines/microsoft-21.jdk/Contents/Home
3. Build: `dotnet build`
Unfortunately, this *fails* for three reasons:
1. `class-parse` crashes when processing JDK-21's `java.base.jmod`.
2. `src/Java.Base` needs updates to bind JDK-21's `java.base.jmod`.
3. On Linux and Windows, Gradle 8.1 and JDK-21 don't mix.
~~ class-parse ~~
This only impacts Debug builds of dotnet/java-interop, but:
% dotnet "bin/Debug-net8.0/class-parse.dll" \
"$HOME/android-toolchain/jdk-21/jmods/java.base.jmod" \
"-o=obj/Debug-net8.0//mcw/api.xml"
…
Process terminated. Assertion failed.
Unexpected number of method parameters in `Ljdk/internal/org/objectweb/asm/commons/JSRInlinerAdapter$Instantiation;.get(Ljava/lang/Object;)Ljava/lang/Object;`: expected 1, got 0
at Xamarin.Android.Tools.Bytecode.MethodInfo.UpdateParametersFromMethodParametersAttribute(ParameterInfo[] parameters) in …/src/Xamarin.Android.Tools.Bytecode/Methods.cs:line 308
…
The assertion?
var pinfo = methodParams.ParameterInfo;
int startIndex = 0;
while (startIndex < pinfo.Count &&
pinfo [startIndex].AccessFlags.HasFlag (.Synthetic))
startIndex++;
Debug.Assert (parameters.Length == pinfo.Count - startIndex, …);
This is part of 4273e5c and 0355acf, attempting to "skip over" the
constructor parameters which non-static inner classes have which
contain the outer class instance:
// Java
class Outer {
/* non-static */ class Inner {
public Inner () { … }
}
}
At the ABI boundary, the `Outer.Inner` constructor is actually:
// "Equivalent" Java for JNI purposes
/* partial */ class Outer {
/* partial */ class Inner {
public Inner (Outer outer) { … } // note added constructor parameter
}
}
and we need to skip over the first parameter.
Which brings us to
`jdk.internal.org.objectweb.asm.commons.JSRInlinerAdapter.Instantiation.get()`:
% mkdir _x
% unzip $HOME/android-toolchain/jdk-21/jmods/java.base.jmod -d _x
% dotnet bin/Debug-net8.0/class-parse.dll --dump \
_x/classes/jdk/internal/org/objectweb/asm/commons/JSRInlinerAdapter\$Instantiation.class
…
8: get (Ljava/lang/Object;)Ljava/lang/Object; Public, Bridge, Synthetic
Code(6, Unknown[LineNumberTable](6), LocalVariableTableAttribute(LocalVariableTableEntry(Name='this', Descriptor='Ljdk/internal/org/objectweb/asm/commons/JSRInlinerAdapter$Instantiation;', StartPC=0, Index=0)))
MethodParametersAttribute(MethodParameterInfo(Name='', AccessFlags=Final, Synthetic))
The parameter for `JSRInlinerAdapter.Instantiation.get(Object)` is
`Synthetic`, causing us to skip over it, which is why we have a
parameter mismatch. The thing is, this parameter *shouldn't* be
skipped; the skipping is intended for *constructor* parameters!
Update the code so that the loop only occurs for constructors.
This allows `class-parse` to *not assert*, allowing `src/Java.Base`
to build.
~~ Gradle ~~
Via dotnet/android#9651, `gradle` fails when building
`tools/java-source-utils`, but only on Linux and Windows:
"/mnt/vss/_work/1/s/xamarin-android/external/Java.Interop/build-tools/gradle/gradlew" -d --stacktrace --no-daemon -PjavaSourceVer=11 -PjavaTargetVer=11 jar
…
[org.gradle.internal.buildevents.BuildExceptionReporter]
[org.gradle.internal.buildevents.BuildExceptionReporter] FAILURE: Build failed with an exception.
[org.gradle.internal.buildevents.BuildExceptionReporter]
[org.gradle.internal.buildevents.BuildExceptionReporter] * What went wrong:
[org.gradle.internal.buildevents.BuildExceptionReporter] Could not open settings generic class cache for settings file '/mnt/vss/_work/1/s/xamarin-android/external/Java.Interop/tools/java-source-utils/settings.gradle' (/home/cloudtest/.gradle/caches/8.1.1/scripts/aiw0k2bokig45bv5yvkog3o3j).
[org.gradle.internal.buildevents.BuildExceptionReporter] > BUG! exception in phase 'semantic analysis' in source unit '_BuildScript_' Unsupported class file major version 65
[org.gradle.internal.buildevents.BuildExceptionReporter]
[org.gradle.internal.buildevents.BuildExceptionReporter] * Try:
[org.gradle.internal.buildevents.BuildExceptionReporter] > Run with --scan to get full insights.
[org.gradle.internal.buildevents.BuildExceptionReporter]
[org.gradle.internal.buildevents.BuildExceptionReporter] * Exception is:
[org.gradle.internal.buildevents.BuildExceptionReporter] org.gradle.cache.CacheOpenException: Could not open settings generic class cache for settings file '/mnt/vss/_work/1/s/xamarin-android/external/Java.Interop/tools/java-source-utils/settings.gradle' (/home/cloudtest/.gradle/caches/8.1.1/scripts/aiw0k2bokig45bv5yvkog3o3j).
[org.gradle.internal.buildevents.BuildExceptionReporter] at org.gradle.cache.internal.DefaultPersistentDirectoryStore.open(DefaultPersistentDirectoryStore.java:91)
[org.gradle.internal.buildevents.BuildExceptionReporter] …
[org.gradle.internal.buildevents.BuildExceptionReporter] Caused by: BUG! exception in phase 'semantic analysis' in source unit '_BuildScript_' Unsupported class file major version 65
[org.gradle.internal.buildevents.BuildExceptionReporter] at org.gradle.groovy.scripts.internal.DefaultScriptCompilationHandler.compileScript(DefaultScriptCompilationHandler.java:147)
[org.gradle.internal.buildevents.BuildExceptionReporter] …
[org.gradle.internal.buildevents.BuildExceptionReporter] Caused by: java.lang.IllegalArgumentException: Unsupported class file major version 65
[org.gradle.internal.buildevents.BuildExceptionReporter] at groovyjarjarasm.asm.ClassReader.<init>(ClassReader.java:199)
🤔
As per the [Gradle Compatibility Matrix][1], Java 21 requires
Gradle 8.5 or later. (No idea why this works on macOS…)
Bump to Gradle 8.12, which is the current latest stable version.
~~ TODO ~~
While dotnet/java-interop now *builds* with JDK-21, unit tests don't
fully pass. In particular,
`tests/Xamarin.Android.Tools.Bytecode-Tests` will need to be updated
because `javac` output has changed. (Again.)
[0]: https://learn.microsoft.com/en-us/java/openjdk/download#openjdk-21
[1]: https://docs.gradle.org/8.12/userguide/compatibility.html

Author: jonpryor

build-tools/gradle/gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.1.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.12-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

src/Java.Base/Java.Lang/StringBuffer.cs

@@ -4,5 +4,15 @@
 
 namespaceJava.Lang{
 partialclassStringBuffer:IEnumerable,IEnumerable<char>{
+
+#if JAVA_API_21
+IAppendable?IAppendable.Append(charc)=>
+Append(c);
+IAppendable?IAppendable.Append(ICharSequence?s)=>
+Append(s);
+IAppendable?IAppendable.Append(ICharSequence?s,inta,intb)=>
+Append(s,a,b);
+#endif // JAVA_API_21
+
 }
 }

src/Java.Base/Java.Lang/StringBuilder.cs

@@ -4,5 +4,15 @@
 
 namespaceJava.Lang{
 partialclassStringBuilder:IEnumerable,IEnumerable<char>{
+
+#if JAVA_API_21
+IAppendable?IAppendable.Append(charc)=>
+Append(c);
+IAppendable?IAppendable.Append(ICharSequence?s)=>
+Append(s);
+IAppendable?IAppendable.Append(ICharSequence?s,inta,intb)=>
+Append(s,a,b);
+#endif // JAVA_API_21
+
 }
 }

src/Java.Base/Java.Lang/Thread.cs

@@ -0,0 +1,30 @@
+namespaceJava.Lang{
+partialclassThread{
+
+#if JAVA_API_21
+partialinterfaceIBuilder{
+partialclassIOfPlatformInvoker{
+IBuilder?IBuilder.InheritInheritableThreadLocals(boolvalue)=>
+InheritInheritableThreadLocals(value);
+IBuilder?IBuilder.Name(string?name)=>
+Name(name);
+IBuilder?IBuilder.Name(string?name,longv)=>
+Name(name,v);
+IBuilder?IBuilder.UncaughtExceptionHandler(IUncaughtExceptionHandler?u)=>
+UncaughtExceptionHandler(u);
+}
+partialclassIOfVirtualInvoker{
+IBuilder?IBuilder.InheritInheritableThreadLocals(boolvalue)=>
+InheritInheritableThreadLocals(value);
+IBuilder?IBuilder.Name(string?name)=>
+Name(name);
+IBuilder?IBuilder.Name(string?name,longv)=>
+Name(name,v);
+IBuilder?IBuilder.UncaughtExceptionHandler(IUncaughtExceptionHandler?u)=>
+UncaughtExceptionHandler(u);
+}
+}
+#endif // JAVA_API_21
+
+}
+}

src/Xamarin.Android.Tools.Bytecode/Methods.cs

@@ -300,14 +300,16 @@ void UpdateParametersFromMethodParametersAttribute (ParameterInfo[] parameters)
 MethodParameterAccessFlags.Final|MethodParameterAccessFlags.Synthetic;
 varpinfo=methodParams.ParameterInfo;
 intstartIndex=0;
-while(startIndex<pinfo.Count&&
-((pinfo[startIndex].AccessFlags&OuterThis1)==OuterThis1||
-(pinfo[startIndex].AccessFlags&OuterThis2)==OuterThis2)){
+while(IsConstructor&&
+startIndex<pinfo.Count&&
+((pinfo[startIndex].AccessFlags&OuterThis1)==OuterThis1||
+(pinfo[startIndex].AccessFlags&OuterThis2)==OuterThis2)){
 startIndex++;
 }
 Debug.Assert(
 parameters.Length==pinfo.Count-startIndex,
-$"Unexpected number of method parameters in `{DeclaringType.FullJniName}.{Name}{Descriptor}`: expected {parameters.Length}, got {pinfo.Count-startIndex}");
+$"Unexpected number of method parameters in `{DeclaringType.FullJniName}.{Name}{Descriptor}`: expected {parameters.Length}, got {pinfo.Count-startIndex}! "+
+$"pinfo.Count={pinfo.Count}, startIndex={startIndex}, pinfo={string.Join(", ",pinfo.Select(p =>p.ToString()))}");
 intend=Math.Min(parameters.Length,pinfo.Count-startIndex);
 for(inti=0;i<end;++i){
 varp=pinfo[i+startIndex];