From 848f7b0a81b09ef7fa73e842222e969ecab5e8c2 Mon Sep 17 00:00:00 2001
From: scivision <scivision@users.noreply.github.com>
Date: Wed, 15 Feb 2023 08:54:02 -0500
Subject: cmake -E time: use C++11 chrono and better format output

fixes #24415
---
 Source/cmcmd.cxx                             | 24 +++++-------------------
 Tests/RunCMake/CommandLine/E_time-stdout.txt |  2 +-
 2 files changed, 6 insertions(+), 20 deletions(-)

diff --git a/Source/cmcmd.cxx b/Source/cmcmd.cxx
index 21d0cc9..d57b78b 100644
--- a/Source/cmcmd.cxx
+++ b/Source/cmcmd.cxx
@@ -50,10 +50,10 @@
 #endif
 
 #include <array>
+#include <chrono>
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
-#include <ctime>
 #include <iostream>
 #include <memory>
 #include <sstream>
@@ -1104,27 +1104,13 @@ int cmcmd::ExecuteCMakeCommand(std::vector<std::string> const& args,
     if (args[1] == "time" && args.size() > 2) {
       std::vector<std::string> command(args.begin() + 2, args.end());
 
-      clock_t clock_start;
-      clock_t clock_finish;
-      time_t time_start;
-      time_t time_finish;
-
-      time(&time_start);
-      clock_start = clock();
       int ret = 0;
+      auto time_start = std::chrono::steady_clock::now();
       cmSystemTools::RunSingleCommand(command, nullptr, nullptr, &ret);
+      auto time_finish = std::chrono::steady_clock::now();
 
-      clock_finish = clock();
-      time(&time_finish);
-
-      double clocks_per_sec = static_cast<double>(CLOCKS_PER_SEC);
-      std::cout << "Elapsed time: "
-                << static_cast<long>(time_finish - time_start) << " s. (time)"
-                << ", "
-                << static_cast<double>(clock_finish - clock_start) /
-          clocks_per_sec
-                << " s. (clock)"
-                << "\n";
+      std::chrono::duration<double> time_elapsed = time_finish - time_start;
+      std::cout << "Elapsed time (seconds): " << time_elapsed.count() << "\n";
       return ret;
     }
 
diff --git a/Tests/RunCMake/CommandLine/E_time-stdout.txt b/Tests/RunCMake/CommandLine/E_time-stdout.txt
index a51446a..1a5e134 100644
--- a/Tests/RunCMake/CommandLine/E_time-stdout.txt
+++ b/Tests/RunCMake/CommandLine/E_time-stdout.txt
@@ -1,3 +1,3 @@
 ^hello  world
-Elapsed time: [^
+Elapsed time \(seconds\): [^
 ]*$
-- 
cgit v0.12


From bf5512ef5160496d50d948d6c5f6391bb147fce0 Mon Sep 17 00:00:00 2001
From: scivision <scivision@users.noreply.github.com>
Date: Wed, 15 Feb 2023 08:58:20 -0500
Subject: Help:cmake -E time: note overhead included

---
 Help/manual/cmake.1.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Help/manual/cmake.1.rst b/Help/manual/cmake.1.rst
index 76dc883..b729790 100644
--- a/Help/manual/cmake.1.rst
+++ b/Help/manual/cmake.1.rst
@@ -1196,7 +1196,7 @@ Available commands are:
 
 .. option:: time <command> [<args>...]
 
-  Run command and display elapsed time.
+  Run ``<command>`` and display elapsed time (including overhead of CMake frontend).
 
   .. versionadded:: 3.5
     The command now properly passes arguments with spaces or special characters
-- 
cgit v0.12