在启用 Android Studio 3.4-RC3 上的 R8 后，构建失败并出现以下错误。如果使用 android.enableR8=false，则构建成功。
编译期间遇到了未定义的值。这通常是由于无效的 dex 输入引起的，该输入使用了一个在导致使用的所有控制流路径上都没有定义的寄存器。
什么是未定义的值，如何修复此错误？
> Task :app:transformClassesAndResourcesWithR8ForStageInternal FAILED
D8: Undefined value encountered during compilation. This is typically caused by invalid dex input that uses a register that is not define on all control-flow paths leading to the use.
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':app:transformClassesAndResourcesWithR8ForStageInternal'.
> com.android.tools.r8.CompilationFailedException: Compilation failed to complete
* Try:
Run with --info or --debug option to get more log output. Run with --scan to get full insights.
* Exception is:
org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':app:transformClassesAndResourcesWithR8ForStageInternal'.
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$2.accept(ExecuteActionsTaskExecuter.java:121)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$2.accept(ExecuteActionsTaskExecuter.java:117)
at org.gradle.internal.Try$Failure.ifSuccessfulOrElse(Try.java:184)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:110)
at org.gradle.api.internal.tasks.execution.ResolveIncrementalChangesTaskExecuter.execute(ResolveIncrementalChangesTaskExecuter.java:84)
at org.gradle.api.internal.tasks.execution.ResolveTaskOutputCachingStateExecuter.execute(ResolveTaskOutputCachingStateExecuter.java:92)
at org.gradle.api.internal.tasks.execution.FinishSnapshotTaskInputsBuildOperationTaskExecuter.execute(FinishSnapshotTaskInputsBuildOperationTaskExecuter.java:51)
at org.gradle.api.internal.tasks.execution.ResolveBuildCacheKeyExecuter.execute(ResolveBuildCacheKeyExecuter.java:103)
at org.gradle.api.internal.tasks.execution.ResolveBeforeExecutionStateTaskExecuter.execute(ResolveBeforeExecutionStateTaskExecuter.java:75)
at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:58)
at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:110)
at org.gradle.api.internal.tasks.execution.ResolveBeforeExecutionOutputsTaskExecuter.execute(ResolveBeforeExecutionOutputsTaskExecuter.java:67)
at org.gradle.api.internal.tasks.execution.StartSnapshotTaskInputsBuildOperationTaskExecuter.execute(StartSnapshotTaskInputsBuildOperationTaskExecuter.java:52)
at org.gradle.api.internal.tasks.execution.ResolveAfterPreviousExecutionStateTaskExecuter.execute(ResolveAfterPreviousExecutionStateTaskExecuter.java:46)
at org.gradle.api.internal.tasks.execution.CleanupStaleOutputsExecuter.execute(CleanupStaleOutputsExecuter.java:94)
at org.gradle.api.internal.tasks.execution.FinalizePropertiesTaskExecuter.execute(FinalizePropertiesTaskExecuter.java:46)
at org.gradle.api.internal.tasks.execution.ResolveTaskExecutionModeExecuter.execute(ResolveTaskExecutionModeExecuter.java:95)
at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:57)
at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:56)
at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:36)
at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.executeTask(EventFiringTaskExecuter.java:63)
at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.call(EventFiringTaskExecuter.java:49)
at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.call(EventFiringTaskExecuter.java:46)
at org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:416)
at org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:406)
at org.gradle.internal.operations.DefaultBuildOperationExecutor$1.execute(DefaultBuildOperationExecutor.java:165)
at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:250)
at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:158)
at org.gradle.internal.operations.DefaultBuildOperationExecutor.call(DefaultBuildOperationExecutor.java:102)
at org.gradle.internal.operations.DelegatingBuildOperationExecutor.call(DelegatingBuildOperationExecutor.java:36)
at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter.execute(EventFiringTaskExecuter.java:46)
at org.gradle.execution.plan.LocalTaskNodeExecutor.execute(LocalTaskNodeExecutor.java:43)
at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$InvokeNodeExecutorsAction.execute(DefaultTaskExecutionGraph.java:355)
at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$InvokeNodeExecutorsAction.execute(DefaultTaskExecutionGraph.java:343)
at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareExecutionAction.execute(DefaultTaskExecutionGraph.java:336)
at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareExecutionAction.execute(DefaultTaskExecutionGraph.java:322)
at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker$1.execute(DefaultPlanExecutor.java:134)
at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker$1.execute(DefaultPlanExecutor.java:129)
at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.execute(DefaultPlanExecutor.java:202)
at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.executeNextNode(DefaultPlanExecutor.java:193)
at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.run(DefaultPlanExecutor.java:129)
at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:46)
at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
Caused by: java.lang.RuntimeException: com.android.tools.r8.CompilationFailedException: Compilation failed to complete
at com.android.builder.profile.Recorder$Block.handleException(Recorder.java:55)
at com.android.builder.profile.ThreadRecorder.record(ThreadRecorder.java:104)
at com.android.build.gradle.internal.pipeline.TransformTask.transform(TransformTask.java:230)
at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:103)
at org.gradle.api.internal.project.taskfactory.IncrementalTaskAction.doExecute(IncrementalTaskAction.java:73)
at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:41)
at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:28)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$4.run(ExecuteActionsTaskExecuter.java:337)
at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:402)
at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:394)
at org.gradle.internal.operations.DefaultBuildOperationExecutor$1.execute(DefaultBuildOperationExecutor.java:165)
at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:250)
at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:158)
at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:92)
at org.gradle.internal.operations.DelegatingBuildOperationExecutor.run(DelegatingBuildOperationExecutor.java:31)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:326)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:311)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.access$200(ExecuteActionsTaskExecuter.java:75)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$TaskExecution.execute(ExecuteActionsTaskExecuter.java:158)
at org.gradle.internal.execution.impl.steps.ExecuteStep.execute(ExecuteStep.java:46)
at org.gradle.internal.execution.impl.steps.CancelExecutionStep.execute(CancelExecutionStep.java:34)
at org.gradle.internal.execution.impl.steps.TimeoutStep.executeWithoutTimeout(TimeoutStep.java:69)
at org.gradle.internal.execution.impl.steps.TimeoutStep.execute(TimeoutStep.java:49)
at org.gradle.internal.execution.impl.steps.CatchExceptionStep.execute(CatchExceptionStep.java:34)
at org.gradle.internal.execution.impl.steps.CreateOutputsStep.execute(CreateOutputsStep.java:49)
at org.gradle.internal.execution.impl.steps.SnapshotOutputStep.execute(SnapshotOutputStep.java:42)
at org.gradle.internal.execution.impl.steps.SnapshotOutputStep.execute(SnapshotOutputStep.java:28)
at org.gradle.internal.execution.impl.steps.CacheStep.executeWithoutCache(CacheStep.java:136)
at org.gradle.internal.execution.impl.steps.CacheStep.lambda$execute$5(CacheStep.java:86)
at org.gradle.internal.execution.impl.steps.CacheStep.execute(CacheStep.java:85)
at org.gradle.internal.execution.impl.steps.CacheStep.execute(CacheStep.java:37)
at org.gradle.internal.execution.impl.steps.PrepareCachingStep.execute(PrepareCachingStep.java:33)
at org.gradle.internal.execution.impl.steps.StoreSnapshotsStep.execute(StoreSnapshotsStep.java:38)
at org.gradle.internal.execution.impl.steps.StoreSnapshotsStep.execute(StoreSnapshotsStep.java:23)
at org.gradle.internal.execution.impl.steps.SkipUpToDateStep.executeBecause(SkipUpToDateStep.java:95)
at org.gradle.internal.execution.impl.steps.SkipUpToDateStep.lambda$execute$0(SkipUpToDateStep.java:88)
at org.gradle.internal.execution.impl.steps.SkipUpToDateStep.execute(SkipUpToDateStep.java:52)
at org.gradle.internal.execution.impl.steps.SkipUpToDateStep.execute(SkipUpToDateStep.java:36)
at org.gradle.internal.execution.impl.DefaultWorkExecutor.execute(DefaultWorkExecutor.java:34)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:109)
... 40 more
Caused by: com.android.tools.r8.CompilationFailedException: Compilation failed to complete
at com.android.tools.r8.utils.ExceptionUtils.withCompilationHandler(ExceptionUtils.java:81)
at com.android.tools.r8.utils.ExceptionUtils.withR8CompilationHandler(ExceptionUtils.java:50)
at com.android.tools.r8.R8.runForTesting(R8.java:238)
at com.android.tools.r8.R8.run(R8.java:148)
at com.android.builder.dexing.R8Tool.runR8(r8Tool.kt:189)
at com.android.build.gradle.internal.transforms.R8Transform.transform(R8Transform.kt:260)
at com.android.build.gradle.internal.pipeline.TransformTask$2.call(TransformTask.java:239)
at com.android.build.gradle.internal.pipeline.TransformTask$2.call(TransformTask.java:235)
at com.android.builder.profile.ThreadRecorder.record(ThreadRecorder.java:102)
... 78 more
Caused by: com.android.tools.r8.utils.AbortException: Error: Undefined value encountered during compilation. This is typically caused by invalid dex input that uses a register that is not define on all control-flow paths leading to the use.
at com.android.tools.r8.utils.Reporter.failIfPendingErrors(Reporter.java:101)
at com.android.tools.r8.utils.Reporter.fatalError(Reporter.java:72)
at com.android.tools.r8.utils.ExceptionUtils.withCompilationHandler(ExceptionUtils.java:66)
... 86 more