From 38ee29a66af1956b08a881a6ee610fae3455fca8 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Mon, 24 Nov 2025 21:05:14 -0500
Subject: [PATCH] cmUVProcessChain: Build stdout before stderr

This is more intuitive in the case of merged streams.
---
 Source/cmUVProcessChain.cxx | 87 ++++++++++++++++++-------------------
 1 file changed, 43 insertions(+), 44 deletions(-)

diff --git a/Source/cmUVProcessChain.cxx b/Source/cmUVProcessChain.cxx
index 2462dabfc2..d0e97ed253 100644
--- a/Source/cmUVProcessChain.cxx
+++ b/Source/cmUVProcessChain.cxx
@@ -219,6 +219,38 @@ bool cmUVProcessChain::InternalData::Prepare(
       break;
   }
 
+  auto const& output =
+    this->Builder->Stdio[cmUVProcessChainBuilder::Stream_OUTPUT];
+  auto& outputData = this->OutputStreamData;
+  switch (output.Type) {
+    case cmUVProcessChainBuilder::None:
+      outputData.Stdio.flags = UV_IGNORE;
+      break;
+
+    case cmUVProcessChainBuilder::Builtin: {
+      int pipeFd[2];
+      if (cmGetPipes(pipeFd) < 0) {
+        return false;
+      }
+
+      outputData.BuiltinStream = pipeFd[0];
+      outputData.Stdio.flags = UV_INHERIT_FD;
+      outputData.Stdio.data.fd = pipeFd[1];
+
+      if (this->TempOutputPipe.init(*this->Loop, 0) < 0) {
+        return false;
+      }
+      if (uv_pipe_open(this->TempOutputPipe, outputData.Stdio.data.fd) < 0) {
+        return false;
+      }
+    } break;
+
+    case cmUVProcessChainBuilder::External:
+      outputData.Stdio.flags = UV_INHERIT_FD;
+      outputData.Stdio.data.fd = output.FileDescriptor;
+      break;
+  }
+
   auto const& error =
     this->Builder->Stdio[cmUVProcessChainBuilder::Stream_ERROR];
   auto& errorData = this->ErrorStreamData;
@@ -228,66 +260,33 @@ bool cmUVProcessChain::InternalData::Prepare(
       break;
 
     case cmUVProcessChainBuilder::Builtin: {
-      int pipeFd[2];
-      if (cmGetPipes(pipeFd) < 0) {
-        return false;
-      }
-
-      errorData.BuiltinStream = pipeFd[0];
-      errorData.Stdio.flags = UV_INHERIT_FD;
-      errorData.Stdio.data.fd = pipeFd[1];
-
-      if (this->TempErrorPipe.init(*this->Loop, 0) < 0) {
-        return false;
-      }
-      if (uv_pipe_open(this->TempErrorPipe, errorData.Stdio.data.fd) < 0) {
-        return false;
-      }
-
-      break;
-    }
-
-    case cmUVProcessChainBuilder::External:
-      errorData.Stdio.flags = UV_INHERIT_FD;
-      errorData.Stdio.data.fd = error.FileDescriptor;
-      break;
-  }
-
-  auto const& output =
-    this->Builder->Stdio[cmUVProcessChainBuilder::Stream_OUTPUT];
-  auto& outputData = this->OutputStreamData;
-  switch (output.Type) {
-    case cmUVProcessChainBuilder::None:
-      outputData.Stdio.flags = UV_IGNORE;
-      break;
-
-    case cmUVProcessChainBuilder::Builtin:
       if (this->Builder->MergedBuiltinStreams) {
-        outputData.BuiltinStream = errorData.BuiltinStream;
-        outputData.Stdio.flags = UV_INHERIT_FD;
-        outputData.Stdio.data.fd = errorData.Stdio.data.fd;
+        errorData.BuiltinStream = outputData.BuiltinStream;
+        errorData.Stdio.flags = UV_INHERIT_FD;
+        errorData.Stdio.data.fd = outputData.Stdio.data.fd;
       } else {
         int pipeFd[2];
         if (cmGetPipes(pipeFd) < 0) {
           return false;
         }
 
-        outputData.BuiltinStream = pipeFd[0];
-        outputData.Stdio.flags = UV_INHERIT_FD;
-        outputData.Stdio.data.fd = pipeFd[1];
+        errorData.BuiltinStream = pipeFd[0];
+        errorData.Stdio.flags = UV_INHERIT_FD;
+        errorData.Stdio.data.fd = pipeFd[1];
 
-        if (this->TempOutputPipe.init(*this->Loop, 0) < 0) {
+        if (this->TempErrorPipe.init(*this->Loop, 0) < 0) {
           return false;
         }
-        if (uv_pipe_open(this->TempOutputPipe, outputData.Stdio.data.fd) < 0) {
+        if (uv_pipe_open(this->TempErrorPipe, errorData.Stdio.data.fd) < 0) {
           return false;
         }
       }
       break;
+    }
 
     case cmUVProcessChainBuilder::External:
-      outputData.Stdio.flags = UV_INHERIT_FD;
-      outputData.Stdio.data.fd = output.FileDescriptor;
+      errorData.Stdio.flags = UV_INHERIT_FD;
+      errorData.Stdio.data.fd = error.FileDescriptor;
       break;
   }