fix: don't inline constants in synchronized statement (#799)

jadx-core/src/main/java/jadx/core/dex/visitors/ConstInlineVisitor.java

@@ -82,6 +82,10 @@ public class ConstInlineVisitor extends AbstractVisitor {
 				}
 				return;
 			}
+			// don't inline const values in synchronized statement
+			if (checkForSynchronizeBlock(insn, sVar)) {
+				return;
+			}
 		} else if (insnType == InsnType.CONST_STR) {
 			if (sVar.isUsedInPhi()) {
 				return;
@@ -108,6 +112,20 @@ public class ConstInlineVisitor extends AbstractVisitor {
 		replaceConst(mth, insn, constArg, toRemove);
 	}
 
+	private static boolean checkForSynchronizeBlock(InsnNode insn, SSAVar ssaVar) {
+		for (RegisterArg reg : ssaVar.getUseList()) {
+			InsnNode parentInsn = reg.getParentInsn();
+			if (parentInsn != null) {
+				InsnType insnType = parentInsn.getType();
+				if (insnType == InsnType.MONITOR_ENTER || insnType == InsnType.MONITOR_EXIT) {
+					insn.add(AFlag.DONT_INLINE);
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
 	private static boolean checkForFinallyBlock(SSAVar sVar) {
 		List<SSAVar> ssaVars = sVar.getCodeVar().getSsaVars();
 		if (ssaVars.size() <= 1) {

jadx-core/src/main/java/jadx/core/dex/visitors/regions/RegionMaker.java

@@ -608,6 +608,7 @@ public class RegionMaker {
 		visited.add(block);
 		for (InsnNode insn : block.getInstructions()) {
 			if (insn.getType() == InsnType.MONITOR_EXIT
+					&& insn.getArgsCount() > 0
 					&& insn.getArg(0).equals(arg)) {
 				exits.add(block);
 				region.getExitInsns().add(insn);

jadx-core/src/test/java/jadx/tests/api/utils/assertj/JadxClassNodeAssertions.java

@@ -16,6 +16,8 @@ public class JadxClassNodeAssertions extends AbstractAssert<JadxClassNodeAsserti
 		isNotNull();
 		ICodeInfo code = actual.getCode();
 		assertThat(code).isNotNull();
-		return new JadxCodeAssertions(code.getCodeStr());
+		String codeStr = code.getCodeStr();
+		assertThat(codeStr).isNotBlank();
+		return new JadxCodeAssertions(codeStr);
 	}
 }

jadx-core/src/test/java/jadx/tests/integration/synchronize/TestNestedSynchronize.java

@@ -0,0 +1,30 @@
+package jadx.tests.integration.synchronize;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.tests.api.SmaliTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+
+public class TestNestedSynchronize extends SmaliTest {
+
+	// @formatter:off
+	/*
+		public final void test() {
+			Object obj = null;
+			Object obj2 = null;
+			synchronized (obj) {
+				synchronized (obj2) {
+				}
+			}
+		}
+	*/
+	// @formatter:on
+
+	@Test
+	public void test() {
+		assertThat(getClassNodeFromSmali())
+				.code()
+				.countString(2, "synchronized");
+	}
+}

jadx-core/src/test/smali/synchronize/TestNestedSynchronize.smali

@@ -0,0 +1,14 @@
+.class public final Lsynchronize/TestNestedSynchronize;
+.super Ljava/lang/Object;
+.source "TestNestedSynchronize.java"
+
+.method public final test()V
+    .locals 2
+    const/4 v0, 0
+    const/4 v1, 0
+    monitor-enter v0
+    monitor-enter v1
+    monitor-exit v1
+    monitor-exit v0
+    return-void
+.end method