Enable shared arena support by default

Author: fangerer

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/SubstrateOptions.java

@@ -1475,12 +1475,8 @@ public static boolean isForeignAPIEnabled() {
     public static final HostedOptionKey<Boolean> VectorAPISupport = new HostedOptionKey<>(false);
 
     @Option(help = "Enable support for Arena.ofShared ", type = Expert)//
-    public static final HostedOptionKey<Boolean> SharedArenaSupport = new HostedOptionKey<>(false, key -> {
-        if (key.getValue()) {
-            UserError.guarantee(isForeignAPIEnabled(), "Support for Arena.ofShared is only available with foreign API support. " +
-                            "Enable foreign API support with %s",
-                            SubstrateOptionsParser.commandArgument(ForeignAPISupport, "+"));
-
+    public static final HostedOptionKey<Boolean> SharedArenaSupport = new HostedOptionKey<>(true, key -> {
+        if (isSharedArenaSupportEnabled()) {
             // GR-65162: Shared arenas cannot be used together with Vector API support
             UserError.guarantee(!VectorAPIEnabled.getValue(), "Support for Arena.ofShared is not available with Vector API support. " +
                             "Either disable Vector API support using %s or replace usages of Arena.ofShared with Arena.ofAuto and disable shared arena support.",

substratevm/src/com.oracle.svm.hosted.foreign/src/com/oracle/svm/hosted/foreign/ForeignFunctionsFeature.java

@@ -48,6 +48,7 @@
 import java.util.function.Supplier;
 import java.util.function.UnaryOperator;
 
+import com.oracle.svm.core.thread.JavaThreads;
 import org.graalvm.collections.EconomicSet;
 import org.graalvm.nativeimage.AnnotationAccess;
 import org.graalvm.nativeimage.ImageSingletons;
@@ -764,6 +765,7 @@ protected void initSafeArenaAccessors(BeforeAnalysisAccessImpl access) throws No
         registerSafeArenaAccessorMethod(metaAccess, ReflectionUtil.lookupMethod(mappedMemoryUtils, "unload", long.class, boolean.class, long.class));
         registerSafeArenaAccessorMethod(metaAccess, ReflectionUtil.lookupMethod(SubstrateMappedMemoryUtils.class, "load", long.class, boolean.class, long.class));
         registerSafeArenaAccessorMethod(metaAccess, Thread.class.getMethod("currentThread"));
+        registerSafeArenaAccessorMethod(metaAccess, JavaThreads.class.getMethod("getCurrentThreadOrNull"));
 
         /*
          * The actual method checking a valid session state (if not inlined) is also safe as this