1 files changed, 17 insertions, 6 deletions
diff --git a/Source/CTest/cmCTestTestHandler.cxx b/Source/CTest/cmCTestTestHandler.cxx
index 957806a..b75df27 100644
--- a/Source/CTest/cmCTestTestHandler.cxx
+++ b/Source/CTest/cmCTestTestHandler.cxx
@@ -550,9 +550,21 @@ bool cmCTestTestHandler::ProcessOptions()
       return false;
     }
   }
-  if (this->GetOption("ParallelLevel")) {
-    this->CTest->SetParallelLevel(
-      std::stoi(*this->GetOption("ParallelLevel")));
+  if (cmValue parallelLevel = this->GetOption("ParallelLevel")) {
+    if (parallelLevel.IsEmpty()) {
+      // An empty value tells ctest to choose a default.
+      this->CTest->SetParallelLevel(cm::nullopt);
+    } else {
+      // A non-empty value must be a non-negative integer.
+      unsigned long plevel = 0;
+      if (!cmStrToULong(*parallelLevel, &plevel)) {
+        cmCTestLog(this->CTest, ERROR_MESSAGE,
+                   "ParallelLevel invalid value: " << *parallelLevel
+                                                   << std::endl);
+        return false;
+      }
+      this->CTest->SetParallelLevel(plevel);
+    }
   }
 
   if (this->GetOption("StopOnFailure")) {
@@ -1360,10 +1372,9 @@ bool cmCTestTestHandler::ProcessDirectory(std::vector<std::string>& passed,
   this->StartTestTime = std::chrono::system_clock::now();
   auto elapsed_time_start = std::chrono::steady_clock::now();
 
-  auto parallel = cm::make_unique<cmCTestMultiProcessHandler>();
-  parallel->SetCTest(this->CTest);
+  auto parallel =
+    cm::make_unique<cmCTestMultiProcessHandler>(this->CTest, this);
   parallel->SetParallelLevel(this->CTest->GetParallelLevel());
-  parallel->SetTestHandler(this);
   if (this->RepeatMode != cmCTest::Repeat::Never) {
     parallel->SetRepeatMode(this->RepeatMode, this->RepeatCount);
   } else {