fix: remove unused ExcHandlers blocks (PR #2086)

* Removing unused ExcHandlers blocks

* Improving removing unused ExcHandlers blocks

* Removing gradlew of the commit

* Adding test 2 for UnreachableCatch

* Update jadx-core/src/test/java/jadx/tests/integration/trycatch/TestUnreachableCatch2.java

---------

Co-authored-by: Away-pp <vladimir@DESKTOP-KESF23K>
Co-authored-by: skylot <[email protected]>

jadx-core/src/main/java/jadx/core/dex/visitors/blocks/BlockExceptionHandler.java

@@ -41,6 +41,7 @@
 import jadx.core.utils.BlockUtils;
 import jadx.core.utils.InsnRemover;
 import jadx.core.utils.ListUtils;
+import jadx.core.utils.blocks.BlockSet;
 import jadx.core.utils.exceptions.JadxRuntimeException;
 
 public class BlockExceptionHandler {
@@ -65,6 +66,10 @@ public static boolean process(MethodNode mth) {
 			removeMonitorExitFromExcHandler(mth, eh);
 		}
 		BlockProcessor.removeMarkedBlocks(mth);
+
+		BlockSet sorted = new BlockSet(mth);
+		BlockUtils.dfsVisit(mth, sorted::set);
+		removeUnusedExcHandlers(mth, tryBlocks, sorted);
 		return true;
 	}
 
@@ -586,4 +591,27 @@ private static int compareByTypeAndName(Comparator<ArgType> comparator, ClassInf
 		}
 		return r;
 	}
+
+	/**
+	 * Remove excHandlers that were not used when connecting.
+	 * Check first if the blocks are unreachable.
+	 */
+	private static void removeUnusedExcHandlers(MethodNode mth, List<TryCatchBlockAttr> tryBlocks, BlockSet blocks) {
+		for (ExceptionHandler eh : mth.getExceptionHandlers()) {
+			boolean notProcessed = true;
+			BlockNode handlerBlock = eh.getHandlerBlock();
+			if (blocks.get(handlerBlock)) {
+				continue;
+			}
+			for (TryCatchBlockAttr tcb : tryBlocks) {
+				if (tcb.getHandlers().contains(handlerBlock)) {
+					notProcessed = false;
+					break;
+				}
+			}
+			if (notProcessed) {
+				BlockProcessor.removeUnreachableBlock(handlerBlock, mth);
+			}
+		}
+	}
 }

jadx-core/src/main/java/jadx/core/dex/visitors/blocks/BlockProcessor.java

@@ -646,10 +646,24 @@ public static void removeMarkedBlocks(MethodNode mth) {
 	private static void removeUnreachableBlocks(MethodNode mth) {
 		Set<BlockNode> toRemove = new LinkedHashSet<>();
 		for (BlockNode block : mth.getBasicBlocks()) {
-			if (block.getPredecessors().isEmpty() && block != mth.getEnterBlock()) {
-				BlockSplitter.collectSuccessors(block, mth.getEnterBlock(), toRemove);
-			}
+			computeUnreachableFromBlock(toRemove, block, mth);
+		}
+		removeFromMethod(toRemove, mth);
+	}
+
+	public static void removeUnreachableBlock(BlockNode blockToRemove, MethodNode mth) {
+		Set<BlockNode> toRemove = new LinkedHashSet<>();
+		computeUnreachableFromBlock(toRemove, blockToRemove, mth);
+		removeFromMethod(toRemove, mth);
+	}
+
+	private static void computeUnreachableFromBlock(Set<BlockNode> toRemove, BlockNode block, MethodNode mth) {
+		if (block.getPredecessors().isEmpty() && block != mth.getEnterBlock()) {
+			BlockSplitter.collectSuccessors(block, mth.getEnterBlock(), toRemove);
 		}
+	}
+
+	private static void removeFromMethod(Set<BlockNode> toRemove, MethodNode mth) {
 		if (toRemove.isEmpty()) {
 			return;
 		}

jadx-core/src/test/java/jadx/tests/integration/trycatch/TestUnreachableCatch.java

@@ -0,0 +1,70 @@
+package jadx.tests.integration.trycatch;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.core.dex.nodes.ClassNode;
+import jadx.tests.api.SmaliTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+@SuppressWarnings("CommentedOutCode")
+public class TestUnreachableCatch extends SmaliTest {
+
+	// @formatter:off
+	/*
+		private static Map<Uri, ByteBuffer> prepareFontData(Context context, FontInfo[] fonts,
+			CancellationSignal cancellationSignal) {
+		final HashMap<Uri, ByteBuffer> out = new HashMap<>();
+		final ContentResolver resolver = context.getContentResolver();
+
+		for (FontInfo font : fonts) {
+			if (font.getResultCode() != Columns.RESULT_CODE_OK) {
+				continue;
+			}
+
+			final Uri uri = font.getUri();
+			if (out.containsKey(uri)) {
+				continue;
+			}
+
+			ByteBuffer buffer = null;
+			try (final ParcelFileDescriptor pfd =
+					resolver.openFileDescriptor(uri, "r", cancellationSignal)) {
+				if (pfd != null) {
+					try (final FileInputStream fis =
+							new FileInputStream(pfd.getFileDescriptor())) {
+						final FileChannel fileChannel = fis.getChannel();
+						final long size = fileChannel.size();
+						buffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, 0, size);
+					} catch (IOException e) {
+						// ignore
+					}
+				}
+			} catch (IOException e) {
+				// ignore
+			}
+
+			// TODO: try other approach?, e.g. read all contents instead of mmap.
+
+			out.put(uri, buffer);
+		}
+		return Collections.unmodifiableMap(out);
+	}
+
+	*/
+	// @formatter:on
+
+	@Test
+	public void test() {
+		disableCompilation();
+		allowWarnInCode();
+
+		ClassNode cls = getClassNodeFromSmali();
+		String code = cls.getCode().toString();
+
+		assertThat(code, containsString("IOException"));
+		assertThat(code, containsString("Collections.unmodifiableMap"));
+	}
+}

jadx-core/src/test/java/jadx/tests/integration/trycatch/TestUnreachableCatch2.java

@@ -0,0 +1,58 @@
+package jadx.tests.integration.trycatch;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.tests.api.SmaliTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+@SuppressWarnings("CommentedOutCode")
+public class TestUnreachableCatch2 extends SmaliTest {
+
+	public static class UnusedExceptionHandlers1 implements AutoCloseable {
+		public static void doSomething(final Object unused1, final Object[] array, final Object o1,
+				final Object o2, final Object unused2) {
+			for (final Object item : array) {
+				ByteBuffer buffer = null;
+				try (final UnusedExceptionHandlers1 u = doSomething2(o1, "", o2)) {
+					try (final FileInputStream fis = new FileInputStream(u.getFilename())) {
+						final FileChannel fileChannel = fis.getChannel();
+						buffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, 0, 42);
+					} catch (final IOException e) {
+						// ignore
+					}
+				} catch (final IOException e) {
+					// ignore
+				}
+			}
+		}
+
+		private String getFilename() {
+			return null;
+		}
+
+		private static UnusedExceptionHandlers1 doSomething2(final Object o1, final String s,
+				final Object o2) {
+			return null;
+		}
+
+		@Override
+		public void close() throws IOException {
+		}
+	}
+
+	@Test
+	public void test() {
+		// TODO: result code not compilable because of 'break' after 'throw'
+		disableCompilation();
+		String code = getClassNode(UnusedExceptionHandlers1.class).getCode().toString();
+		assertThat(code, containsString("IOException"));
+	}
+}