[GR-68166] Add ImageHeapMetadataDumpFileName native image build option and NativeImageHeap.dumpMetadata method

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

@@ -1370,6 +1370,11 @@ public Boolean getValue(OptionValues values) {
     @Option(help = "Create a heap dump and exit.")//
     public static final RuntimeOptionKey<Boolean> DumpHeapAndExit = new RuntimeOptionKey<>(false, Immutable);
 
+    @Option(help = "Name of a csv file into which image heap metadata should be dumped. " +
+                    "This csv file will be located in the same directory as the image. " +
+                    "If this option is an empty string, the metadata will not be dumped.") //
+    public static final HostedOptionKey<String> ImageHeapMetadataDumpFileName = new HostedOptionKey<>("");
+
     @Option(help = "Print some VM information and exit.")//
     public static final RuntimeOptionKey<Boolean> PrintVMInfoAndExit = new RuntimeOptionKey<>(false, Immutable);
 

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/NativeImage.java

@@ -561,6 +561,7 @@ public void build(String imageName, DebugContext debug) {
             // We print the heap statistics after the heap was successfully written because this
             // could modify objects that will be part of the image heap.
             printHeapStatistics(heap.getLayouter().getPartitions());
+            heap.dumpMetadata();
         }
     }
 

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/NativeImageHeap.java

@@ -26,8 +26,13 @@
 
 import static com.oracle.svm.core.util.VMError.shouldNotReachHereUnexpectedInput;
 
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
 import java.lang.reflect.Array;
 import java.lang.reflect.Modifier;
+import java.nio.file.Path;
 import java.util.ArrayDeque;
 import java.util.Arrays;
 import java.util.Collection;
@@ -41,6 +46,7 @@
 import java.util.Set;
 import java.util.function.Predicate;
 
+import com.oracle.svm.core.option.HostedOptionValues;
 import org.graalvm.nativeimage.ImageSingletons;
 import org.graalvm.nativeimage.c.function.RelocatedPointer;
 import org.graalvm.word.UnsignedWord;
@@ -792,6 +798,35 @@ public ObjectInfo addLateToImageHeap(Object object, Object reason) {
         return addToImageHeap(object, (HostedClass) type, getSize(object, type), System.identityHashCode(object), reason);
     }
 
+    /**
+     * Dumps metadata for every object in the image heap.
+     */
+    public void dumpMetadata() {
+        String metadataFileName = SubstrateOptions.ImageHeapMetadataDumpFileName.getValue();
+        if (metadataFileName == null || metadataFileName.isEmpty()) {
+            // Do not dump metadata if the file name isn't set
+            return;
+        }
+
+        Path metadataFilePath = SubstrateOptions.getImagePath(HostedOptionValues.singleton()).resolve(metadataFileName);
+        File metadataFile = metadataFilePath.toFile();
+        String metadataDir = metadataFile.getParent();
+        if (!new File(metadataDir).exists()) {
+            throw VMError.shouldNotReachHere("Image heap metadata directory does not exist: " + metadataDir);
+        }
+
+        try (FileWriter metadataOut = new FileWriter(metadataFile);
+                        BufferedWriter metadataBw = new BufferedWriter(metadataOut)) {
+            metadataBw.write("class-name,partition,offset-in-heap,size\n");
+            for (ObjectInfo info : getObjects()) {
+                String csvLine = info.getClazz().getName() + "," + info.getPartition().getName() + "," + info.getOffset() + "," + info.getSize() + System.lineSeparator();
+                metadataBw.write(csvLine);
+            }
+        } catch (IOException ex) {
+            throw new RuntimeException("Failed to dump image heap metadata to " + metadataFile, ex);
+        }
+    }
+
     private long getSize(Object object, HostedType type) {
         if (type.isInstanceClass()) {
             HostedInstanceClass clazz = (HostedInstanceClass) type;