Add OutHeapMetadataPath native image build option and NativeImageHeap.dumpMetadata method.

Author: Andrija Kolic

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

@@ -1364,6 +1364,19 @@ public Boolean getValue(OptionValues values) {
                     "the default file name.") //
     public static final RuntimeOptionKey<String> HeapDumpPath = new RuntimeOptionKey<>("", Immutable);
 
+    @Option(help = "Path of the file in which heap metadata should be dumped. " +
+                    "If this option is an empty string, the metadata will not be dumped.")//
+    public static final HostedOptionKey<String> OutHeapMetadataPath = new HostedOptionKey<>("") {
+        @Override
+        protected void onValueUpdate(EconomicMap<OptionKey<?>, Object> values, String oldValue, String newValue) {
+            if (newValue != null && !newValue.trim().isEmpty()) {
+                GenerateDebugInfo.update(values, 2);
+                DeleteLocalSymbols.update(values, false);
+                PreserveFramePointer.update(values, true);
+            }
+        }
+    };
+
     @Option(help = "A prefix that is used for heap dump filenames if no heap dump filename was specified explicitly.")//
     public static final HostedOptionKey<String> HeapDumpDefaultFilenamePrefix = new HostedOptionKey<>("svm-heapdump-");
 

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

@@ -562,6 +562,7 @@ 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

@@ -26,6 +26,10 @@
 
 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.util.ArrayDeque;
@@ -793,6 +797,43 @@ 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 heap.
+     */
+    public void dumpMetadata() {
+        final String heapMetadataPath = SubstrateOptions.OutHeapMetadataPath.getValue();
+        if (heapMetadataPath == null || heapMetadataPath.isEmpty()) {
+            // Do not dump metadata if the path isn't set
+            return;
+        }
+
+        final File metadataFile = new File(heapMetadataPath);
+        final String heapMetadataDir = metadataFile.getParent();
+        if (!new File(heapMetadataDir).exists()) {
+            throw VMError.shouldNotReachHere("Heap metadata directory does not exist: " + heapMetadataDir);
+        }
+
+        try (
+                        final FileWriter metadataOut = new FileWriter(metadataFile);
+                        final BufferedWriter metadataBw = new BufferedWriter(metadataOut)) {
+            metadataBw.write("class-name,partition,offset-in-heap,size\n");
+            for (final ObjectInfo info : getObjects()) {
+                try {
+                    metadataBw.write(
+                                    info.getClazz().getName() + "," +
+                                                    info.getPartition().getName() + "," +
+                                                    info.getOffset() + "," +
+                                                    info.getSize() + System.lineSeparator());
+                } catch (final Throwable ex) {
+                    // do nothing
+                    // write next
+                }
+            }
+        } catch (final IOException ex) {
+            // do nothing
+        }
+    }
+
     private long getSize(Object object, HostedType type) {
         if (type.isInstanceClass()) {
             HostedInstanceClass clazz = (HostedInstanceClass) type;