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, 10 insertions, 6 deletions

diff --git a/Source/CTest/cmCTestBuildHandler.cxx b/Source/CTest/cmCTestBuildHandler.cxx
index f4fc769..4ad4831 100644
--- a/Source/CTest/cmCTestBuildHandler.cxx
+++ b/Source/CTest/cmCTestBuildHandler.cxx
@@ -17,6 +17,7 @@
 #include <set>
 #include <stdlib.h>
 #include <string.h>
+#include <type_traits>
 
 static const char* cmCTestErrorMatches[] = {
   "^[Bb]us [Ee]rror",
@@ -327,7 +328,7 @@ int cmCTestBuildHandler::ProcessHandler()
 
   // Create a last build log
   cmGeneratedFileStream ofs;
-  double elapsed_time_start = cmSystemTools::GetTime();
+  auto elapsed_time_start = std::chrono::steady_clock::now();
   if (!this->StartLogFile("Build", ofs)) {
     cmCTestLog(this->CTest, ERROR_MESSAGE, "Cannot create build log file"
                  << std::endl);
@@ -421,7 +422,8 @@ int cmCTestBuildHandler::ProcessHandler()
   // Remember end build time and calculate elapsed time
   this->EndBuild = this->CTest->CurrentTime();
   this->EndBuildTime = cmSystemTools::GetTime();
-  double elapsed_build_time = cmSystemTools::GetTime() - elapsed_time_start;
+  auto elapsed_build_time =
+    std::chrono::steady_clock::now() - elapsed_time_start;
 
   // Cleanups strings in the errors and warnings list.
   if (!this->SimplifySourceDir.empty()) {
@@ -633,8 +635,8 @@ void cmCTestBuildHandler::GenerateXMLLogScraped(cmXMLWriter& xml)
   }
 }
 
-void cmCTestBuildHandler::GenerateXMLFooter(cmXMLWriter& xml,
-                                            double elapsed_build_time)
+void cmCTestBuildHandler::GenerateXMLFooter(
+  cmXMLWriter& xml, std::chrono::duration<double> elapsed_build_time)
 {
   xml.StartElement("Log");
   xml.Attribute("Encoding", "base64");
@@ -643,8 +645,10 @@ void cmCTestBuildHandler::GenerateXMLFooter(cmXMLWriter& xml,
 
   xml.Element("EndDateTime", this->EndBuild);
   xml.Element("EndBuildTime", static_cast<unsigned int>(this->EndBuildTime));
-  xml.Element("ElapsedMinutes",
-              static_cast<int>(elapsed_build_time / 6) / 10.0);
+  xml.Element(
+    "ElapsedMinutes",
+    std::chrono::duration_cast<std::chrono::minutes>(elapsed_build_time)
+      .count());
   xml.EndElement(); // Build
   this->CTest->EndXML(xml);
 }