Always call CentipedeFinalizeProcessing to report FuzzTest input pr…

…operly.

This is needed because otherwise Centipede would crash for exceeded memory/time limits after FuzzTest cleaning up the current input, leading to undesired "setup failure" reports.
But we don't want Centipede to prepare the coverage twice (which would result in garbage coverage). Thus using the input_start_time as a guard - they should be set to 0 after each iteration anyway.

PiperOrigin-RevId: 706865286

centipede/runner.cc

@@ -614,7 +614,9 @@ static void RunOneInput(const uint8_t *data, size_t size,
   int target_return_value = callbacks.Execute({data, size}) ? 0 : -1;
   state.stats.exec_time_usec = UsecSinceLast();
   CheckWatchdogLimits();
-  PostProcessCoverage(target_return_value);
+  if (centipede::state.input_start_time.exchange(0) != 0) {
+    PostProcessCoverage(target_return_value);
+  }
   state.stats.post_time_usec = UsecSinceLast();
   state.stats.peak_rss_mb = GetPeakRSSMb();
 }
@@ -1235,7 +1237,9 @@ extern "C" void CentipedePrepareProcessing() {
 
 extern "C" void CentipedeFinalizeProcessing() {
   centipede::CheckWatchdogLimits();
-  centipede::PostProcessCoverage(/*target_return_value=*/0);
+  if (centipede::state.input_start_time.exchange(0) != 0) {
+    centipede::PostProcessCoverage(/*target_return_value=*/0);
+  }
 }
 
 extern "C" size_t CentipedeGetExecutionResult(uint8_t *data, size_t capacity) {

centipede/runner_interface.h

@@ -103,6 +103,9 @@ extern "C" void CentipedeEndExecutionBatch();
 extern "C" void CentipedePrepareProcessing();
 
 // Finalizes the processing of an input and stores the state internally.
+//
+// For tool integration, it can be called inside `RunnerCallbacks::Execute()` to
+// finalize the execution early before extra cleanups.
 extern "C" void CentipedeFinalizeProcessing();
 
 // Retrieves the execution results (including coverage information) after

fuzztest/internal/centipede_adaptor.cc

@@ -479,7 +479,7 @@ class CentipedeFixtureDriver : public UntypedFixtureDriver {
     if (runtime_.skipping_requested()) {
       CentipedeSetExecutionResult(nullptr, 0);
     }
-    if (!runner_mode) CentipedeFinalizeProcessing();
+    CentipedeFinalizeProcessing();
   }
 
   void TearDownFuzzTest() override { orig_fixture_driver_->TearDownFuzzTest(); }