CTest: use std::chrono::steady_clock for time keeping

It was reported in issue #17345 that CTest does not use monotonic time
to report test duration. Monotonic clocks are not affected by large NTP
adjustments or things like daylight savings time.

As CMake 3.10 requires C++11, which introduced std::chrono, this commit
moves the time keeping in CTest from cmSystemTools::GetTime() to
std::chrono::steady_clock.

Fixes: #17345

1 files changed, 7 insertions, 5 deletions

diff --git a/Source/CTest/cmCTestConfigureHandler.cxx b/Source/CTest/cmCTestConfigureHandler.cxx
index 56a038e..e732f9f 100644
--- a/Source/CTest/cmCTestConfigureHandler.cxx
+++ b/Source/CTest/cmCTestConfigureHandler.cxx
@@ -7,8 +7,10 @@
 #include "cmSystemTools.h"
 #include "cmXMLWriter.h"
 
+#include <chrono>
 #include <ostream>
 #include <string>
+#include <type_traits>
 
 cmCTestConfigureHandler::cmCTestConfigureHandler()
 {
@@ -43,7 +45,7 @@ int cmCTestConfigureHandler::ProcessHandler()
     return -1;
   }
 
-  double elapsed_time_start = cmSystemTools::GetTime();
+  auto elapsed_time_start = std::chrono::steady_clock::now();
   std::string output;
   int retVal = 0;
   int res = 0;
@@ -84,10 +86,10 @@ int cmCTestConfigureHandler::ProcessHandler()
       xml.Element("EndDateTime", this->CTest->CurrentTime());
       xml.Element("EndConfigureTime",
                   static_cast<unsigned int>(cmSystemTools::GetTime()));
-      xml.Element(
-        "ElapsedMinutes",
-        static_cast<int>((cmSystemTools::GetTime() - elapsed_time_start) / 6) /
-          10.0);
+      xml.Element("ElapsedMinutes",
+                  std::chrono::duration_cast<std::chrono::minutes>(
+                    std::chrono::steady_clock::now() - elapsed_time_start)
+                    .count());
       xml.EndElement(); // Configure
       this->CTest->EndXML(xml);
     }