CTest: Capture test stdout/stderr through one pipe (#15600)

Use the KWSys Process "MergeOutput" option to give each test child
process the same pipe for both stdout and stderr.  This allows natural
merging of stdout and stderr together instead of merging on arbitrary
buffered read boundaries as before.

Source/CTest/cmCTestRunTest.cxx

@@ -57,8 +57,7 @@ bool cmCTestRunTest::CheckOutput()
       // Process has terminated and all output read.
       return false;
       }
-    else if(p == cmsysProcess_Pipe_STDOUT ||
-            p == cmsysProcess_Pipe_STDERR)
+    else if(p == cmsysProcess_Pipe_STDOUT)
       {
       // Store this line of output.
       cmCTestLog(this->CTest, HANDLER_VERBOSE_OUTPUT,

Source/CTest/cmProcess.cxx

@@ -62,6 +62,7 @@ bool cmProcess::StartProcess()
                                      this->WorkingDirectory.c_str());
     }
   cmsysProcess_SetTimeout(this->Process, this->Timeout);
+  cmsysProcess_SetOption(this->Process, cmsysProcess_Option_MergeOutput, 1);
   cmsysProcess_Execute(this->Process);
   return (cmsysProcess_GetState(this->Process)
           == cmsysProcess_State_Executing);
@@ -124,14 +125,10 @@ int cmProcess::GetNextOutputLine(std::string& line, double timeout)
   for(;;)
     {
     // Look for lines already buffered.
-    if(this->StdOut.GetLine(line))
+    if(this->Output.GetLine(line))
       {
       return cmsysProcess_Pipe_STDOUT;
       }
-    else if(this->StdErr.GetLine(line))
-      {
-      return cmsysProcess_Pipe_STDERR;
-      }
 
     // Check for more data from the process.
     char* data;
@@ -143,11 +140,7 @@ int cmProcess::GetNextOutputLine(std::string& line, double timeout)
       }
     else if(p == cmsysProcess_Pipe_STDOUT)
       {
-      this->StdOut.insert(this->StdOut.end(), data, data+length);
-      }
-    else if(p == cmsysProcess_Pipe_STDERR)
-      {
-      this->StdErr.insert(this->StdErr.end(), data, data+length);
+      this->Output.insert(this->Output.end(), data, data+length);
       }
     else // p == cmsysProcess_Pipe_None
       {
@@ -157,14 +150,10 @@ int cmProcess::GetNextOutputLine(std::string& line, double timeout)
     }
 
   // Look for partial last lines.
-  if(this->StdOut.GetLast(line))
+  if(this->Output.GetLast(line))
     {
     return cmsysProcess_Pipe_STDOUT;
     }
-  else if(this->StdErr.GetLast(line))
-    {
-    return cmsysProcess_Pipe_STDERR;
-    }
 
   // No more data.  Wait for process exit.
   if(!cmsysProcess_WaitForExit(this->Process, &timeout))

Source/CTest/cmProcess.h

@@ -48,8 +48,7 @@ public:
    * Read one line of output but block for no more than timeout.
    * Returns:
    *   cmsysProcess_Pipe_None    = Process terminated and all output read
-   *   cmsysProcess_Pipe_STDOUT  = Line came from stdout
-   *   cmsysProcess_Pipe_STDOUT  = Line came from stderr
+   *   cmsysProcess_Pipe_STDOUT  = Line came from stdout or stderr
    *   cmsysProcess_Pipe_Timeout = Timeout expired while waiting
    */
   int GetNextOutputLine(std::string& line, double timeout);
@@ -68,13 +67,11 @@ private:
     bool GetLine(std::string& line);
     bool GetLast(std::string& line);
   };
-  Buffer StdErr;
-  Buffer StdOut;
+  Buffer Output;
   std::string Command;
   std::string WorkingDirectory;
   std::vector<std::string> Arguments;
   std::vector<const char*> ProcessArgs;
-  std::string Output;
   int Id;
   int ExitValue;
 };

Tests/RunCMake/CTestCommandLine/MergeOutput-stdout.txt

@@ -0,0 +1,13 @@
+Test timeout computed to be: [^
+]+
+1: -- Output on stdout
+1: Output on stderr
+1: -- Output on stdout
+1: Output on stderr
+1: -- Output on stdout
+1: Output on stderr
+1: -- Output on stdout
+1: Output on stderr
+1: -- Output on stdout
+1: Output on stderr
+1/1 Test #1: MergeOutput

Tests/RunCMake/CTestCommandLine/MergeOutput.cmake

@@ -0,0 +1,4 @@
+foreach(i RANGE 1 5)
+  message(STATUS "Output on stdout")
+  message("Output on stderr")
+endforeach()

Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake

@@ -39,3 +39,16 @@ subdirs()
   run_cmake_command(BadCTestTestfile ${CMAKE_CTEST_COMMAND})
 endfunction()
 run_BadCTestTestfile()
+
+function(run_MergeOutput)
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/MergeOutput)
+  set(RunCMake_TEST_NO_CLEAN 1)
+  file(REMOVE_RECURSE "${RunCMake_TEST_BINARY_DIR}")
+  file(MAKE_DIRECTORY "${RunCMake_TEST_BINARY_DIR}")
+  file(WRITE "${RunCMake_TEST_BINARY_DIR}/CTestTestfile.cmake" "
+add_test(MergeOutput \"${CMAKE_COMMAND}\" -P \"${RunCMake_SOURCE_DIR}/MergeOutput.cmake\")
+")
+
+  run_cmake_command(MergeOutput ${CMAKE_CTEST_COMMAND} -V)
+endfunction()
+run_MergeOutput()