From 2f5dd171d078fceba3fcc11ff6813bd62fb89b80 Mon Sep 17 00:00:00 2001
From: Jonas Konrad <me@yawk.at>
Date: Wed, 9 Dec 2020 21:19:21 +0100
Subject: [PATCH] fix: do not remove method start block when it is referenced
 from dead code (PR #1044)

---
 .../dex/visitors/blocksmaker/BlockSplitter.java  |  6 +++---
 .../others/TestDeadBlockReferencesStart.java     | 16 ++++++++++++++++
 .../others/TestDeadBlockReferencesStart.smali    | 11 +++++++++++
 3 files changed, 30 insertions(+), 3 deletions(-)
 create mode 100644 jadx-core/src/test/java/jadx/tests/integration/others/TestDeadBlockReferencesStart.java
 create mode 100644 jadx-core/src/test/smali/others/TestDeadBlockReferencesStart.smali

diff --git a/jadx-core/src/main/java/jadx/core/dex/visitors/blocksmaker/BlockSplitter.java b/jadx-core/src/main/java/jadx/core/dex/visitors/blocksmaker/BlockSplitter.java
index 64cd7c28..c73b6555 100644
--- a/jadx-core/src/main/java/jadx/core/dex/visitors/blocksmaker/BlockSplitter.java
+++ b/jadx-core/src/main/java/jadx/core/dex/visitors/blocksmaker/BlockSplitter.java
@@ -339,7 +339,7 @@ public class BlockSplitter extends AbstractVisitor {
 		Set<BlockNode> toRemove = new LinkedHashSet<>();
 		for (BlockNode block : mth.getBasicBlocks()) {
 			if (block.getPredecessors().isEmpty() && block != mth.getEnterBlock()) {
-				collectSuccessors(block, toRemove);
+				collectSuccessors(block, mth.getEnterBlock(), toRemove);
 			}
 		}
 		if (toRemove.isEmpty()) {
@@ -390,7 +390,7 @@ public class BlockSplitter extends AbstractVisitor {
 				&& !block.contains(AFlag.MTH_ENTER_BLOCK);
 	}
 
-	private static void collectSuccessors(BlockNode startBlock, Set<BlockNode> toRemove) {
+	private static void collectSuccessors(BlockNode startBlock, BlockNode methodEnterBlock, Set<BlockNode> toRemove) {
 		Deque<BlockNode> stack = new ArrayDeque<>();
 		stack.add(startBlock);
 		while (!stack.isEmpty()) {
@@ -398,7 +398,7 @@ public class BlockSplitter extends AbstractVisitor {
 			if (!toRemove.contains(block)) {
 				toRemove.add(block);
 				for (BlockNode successor : block.getSuccessors()) {
-					if (toRemove.containsAll(successor.getPredecessors())) {
+					if (successor != methodEnterBlock && toRemove.containsAll(successor.getPredecessors())) {
 						stack.push(successor);
 					}
 				}
diff --git a/jadx-core/src/test/java/jadx/tests/integration/others/TestDeadBlockReferencesStart.java b/jadx-core/src/test/java/jadx/tests/integration/others/TestDeadBlockReferencesStart.java
new file mode 100644
index 00000000..891dbd3e
--- /dev/null
+++ b/jadx-core/src/test/java/jadx/tests/integration/others/TestDeadBlockReferencesStart.java
@@ -0,0 +1,16 @@
+package jadx.tests.integration.others;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.tests.api.SmaliTest;
+
+import static jadx.tests.api.utils.JadxMatchers.countString;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+public class TestDeadBlockReferencesStart extends SmaliTest {
+	@Test
+	public void test() {
+		String code = getClassNodeFromSmali().getCode().getCodeStr();
+		assertThat(code, countString(0, "throw"));
+	}
+}
diff --git a/jadx-core/src/test/smali/others/TestDeadBlockReferencesStart.smali b/jadx-core/src/test/smali/others/TestDeadBlockReferencesStart.smali
new file mode 100644
index 00000000..0c93538b
--- /dev/null
+++ b/jadx-core/src/test/smali/others/TestDeadBlockReferencesStart.smali
@@ -0,0 +1,11 @@
+.class Lothers/TestDeadBlockReferencesStart;
+.super Ljava/lang/Object;
+
+.method public test()V
+    .registers 6
+
+     :start
+     return-void
+
+     goto :start
+.end method
-- 
GitLab