From 1040e690c6c99979f8edf2a121de6d835be96dbe Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Thu, 14 Jan 2016 16:11:23 -0500
Subject: cmSystemTools: Teach RunSingleCommand to merge child pipes when
 possible

Audit the code to make sure there are no callers that use OUTPUT_MERGE
with separate capture strings.  Then change RunSingleCommand to
implement output merging by giving the child process a single pipe for
both its stdout and stderr descriptors.  This will more cleanly merge
the content on atomic write boundaries in the child instead of on
arbitrary buffering boundaries in the parent.
---
 Source/cmSystemTools.cxx | 44 +++++++++++++++++++++-----------------------
 1 file changed, 21 insertions(+), 23 deletions(-)

diff --git a/Source/cmSystemTools.cxx b/Source/cmSystemTools.cxx
index 3a730b2..3ba7287 100644
--- a/Source/cmSystemTools.cxx
+++ b/Source/cmSystemTools.cxx
@@ -17,6 +17,7 @@
 #include <time.h>
 #include <string.h>
 #include <stdlib.h>
+#include <assert.h>
 #ifdef __QNX__
 # include <malloc.h> /* for malloc/free on QNX */
 #endif
@@ -673,7 +674,16 @@ bool cmSystemTools::RunSingleCommand(std::vector<std::string>const& command,
     {
     cmsysProcess_SetPipeShared(cp, cmsysProcess_Pipe_STDOUT, 1);
     cmsysProcess_SetPipeShared(cp, cmsysProcess_Pipe_STDERR, 1);
+    captureStdOut = 0;
+    captureStdErr = 0;
     }
+  else if (outputflag == OUTPUT_MERGE ||
+           (captureStdErr && captureStdErr == captureStdOut))
+    {
+    cmsysProcess_SetOption(cp, cmsysProcess_Option_MergeOutput, 1);
+    captureStdErr = 0;
+    }
+  assert(!captureStdErr || captureStdErr != captureStdOut);
 
   cmsysProcess_SetTimeout(cp, timeout);
   cmsysProcess_Execute(cp);
@@ -699,38 +709,26 @@ bool cmSystemTools::RunSingleCommand(std::vector<std::string>const& command,
           }
         }
 
-      if(pipe == cmsysProcess_Pipe_STDOUT ||
-         (pipe == cmsysProcess_Pipe_STDERR &&
-          captureStdOut == captureStdErr))
+      if (pipe == cmsysProcess_Pipe_STDOUT)
         {
-        if (captureStdOut)
+        if (outputflag != OUTPUT_NONE)
           {
-          tempStdOut.insert(tempStdOut.end(), data, data+length);
+          cmSystemTools::Stdout(data, length);
           }
-        }
-      else if(pipe == cmsysProcess_Pipe_STDERR)
-        {
-        if (captureStdErr)
+        if (captureStdOut)
           {
-          tempStdErr.insert(tempStdErr.end(), data, data+length);
+          tempStdOut.insert(tempStdOut.end(), data, data+length);
           }
         }
-      if(outputflag != OUTPUT_NONE)
+      else if (pipe == cmsysProcess_Pipe_STDERR)
         {
-        if(outputflag == OUTPUT_MERGE)
+        if (outputflag != OUTPUT_NONE)
           {
-          cmSystemTools::Stdout(data, length);
+          cmSystemTools::Stderr(data, length);
           }
-        else
+        if (captureStdErr)
           {
-          if(pipe == cmsysProcess_Pipe_STDERR)
-            {
-            cmSystemTools::Stderr(data, length);
-            }
-          else if(pipe == cmsysProcess_Pipe_STDOUT)
-            {
-            cmSystemTools::Stdout(data, length);
-            }
+          tempStdErr.insert(tempStdErr.end(), data, data+length);
           }
         }
       }
@@ -741,7 +739,7 @@ bool cmSystemTools::RunSingleCommand(std::vector<std::string>const& command,
     {
     captureStdOut->assign(tempStdOut.begin(), tempStdOut.end());
     }
-  if (captureStdErr && captureStdErr != captureStdOut)
+  if (captureStdErr)
     {
     captureStdErr->assign(tempStdErr.begin(), tempStdErr.end());
     }
-- 
cgit v0.12