From b78997d71ddd68247f021bb258f6ffd1e344057b Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Tue, 11 Mar 2008 17:53:54 -0400
Subject: [PATCH] BUG: Fix subtle bug that prevented Makefile generators from
 rescanning dependencies when a new source file is added but no other sources
 are touched.

---
 Source/cmLocalUnixMakefileGenerator3.cxx | 31 +++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/Source/cmLocalUnixMakefileGenerator3.cxx b/Source/cmLocalUnixMakefileGenerator3.cxx
index 396dd75cd..158a01970 100644
--- a/Source/cmLocalUnixMakefileGenerator3.cxx
+++ b/Source/cmLocalUnixMakefileGenerator3.cxx
@@ -24,6 +24,7 @@
 #include "cmSourceFile.h"
 #include "cmake.h"
 #include "cmVersion.h"
+#include "cmFileTimeComparison.h"
 
 // Include dependency scanners for supported languages.  Only the
 // C/C++ scanner is needed for bootstrapping CMake.
@@ -1307,15 +1308,39 @@ bool cmLocalUnixMakefileGenerator3::UpdateDependencies(const char* tgtInfo,
   std::string internalDependFile = dir + "/depend.internal";
   std::string dependFile = dir + "/depend.make";
 
+  // If the target DependInfo.cmake file has changed since the last
+  // time dependencies were scanned then force rescanning.  This may
+  // happen when a new source file is added and CMake regenerates the
+  // project but no other sources were touched.
+  bool needRescan = false;
+  cmFileTimeComparison* ftc =
+    this->GlobalGenerator->GetCMakeInstance()->GetFileComparison();
+  {
+  int result;
+  if(!ftc->FileTimeCompare(internalDependFile.c_str(), tgtInfo, &result) ||
+     result < 0)
+    {
+    if(verbose)
+      {
+      cmOStringStream msg;
+      msg << "Dependee \"" << tgtInfo
+          << "\" is newer than depender \""
+          << internalDependFile << "\"." << std::endl;
+      cmSystemTools::Stdout(msg.str().c_str());
+      }
+    needRescan = true;
+    }
+  }
+
   // Check the implicit dependencies to see if they are up to date.
   // The build.make file may have explicit dependencies for the object
   // files but these will not affect the scanning process so they need
   // not be considered.
   cmDependsC checker;
   checker.SetVerbose(verbose);
-  checker.SetFileComparison
-    (this->GlobalGenerator->GetCMakeInstance()->GetFileComparison());
-  if(!checker.Check(dependFile.c_str(), internalDependFile.c_str()))
+  checker.SetFileComparison(ftc);
+  if(needRescan ||
+     !checker.Check(dependFile.c_str(), internalDependFile.c_str()))
     {
     // The dependencies must be regenerated.
     std::string targetName = cmSystemTools::GetFilenameName(dir);