BUG: Fix to avoid repeated calls to CollapseFullPath during dependency scanning. This addresses bug#3191.

Source/cmDepends.h

@@ -37,6 +37,11 @@ public:
   
   /** at what level will the compile be done from */
   void SetCompileDirectory(const char *dir) {this->CompileDirectory = dir;};
+  
+  /** Set the full path to the top of the build tree.  This is
+      the base path from which dependencies are referenced as
+      relative paths.  */
+  void SetHomeOutputDirectory(const char *dir) {this->HomeOutputDirectory = dir;};
     
   /** should this be verbose in its output */
   void SetVerbose(bool verb) { this->Verbose = verb; }
@@ -71,9 +76,11 @@ protected:
   virtual bool CheckDependencies(std::istream& internalDepends);
 
   // The directory in which the build rule for the target file is executed.
-  std::string Directory;
   std::string CompileDirectory;
 
+  // The full path to the top of the build tree.
+  std::string HomeOutputDirectory;
+
   // Flag for verbose output.
   bool Verbose;
   cmFileTimeComparison* FileComparison;

Source/cmDependsC.cxx

@@ -26,7 +26,6 @@ cmDependsC::cmDependsC():
   IncludePath(0), GeneratedFiles(0)
 {
 }
-
 //----------------------------------------------------------------------------
 // yummy look at all those constructor arguments
 cmDependsC::cmDependsC(std::vector<std::string> const& includes,
@@ -85,6 +84,7 @@ bool cmDependsC::WriteDependencies(const char *src, const char *obj,
   this->Encountered.insert(src);
   std::set<cmStdString> dependencies;
   std::set<cmStdString> scanned;
+
   while(!this->Unscanned.empty())
     {
     // Get the next file to scan.
@@ -367,9 +367,10 @@ bool cmDependsC::FileExistsOrIsGenerated(const std::string& fname,
   else if(cmSystemTools::FileIsFullPath(fname.c_str()))
     {
     // The generated file may have been listed with a relative path.
-    std::string dir = cmSystemTools::CollapseFullPath(this->Directory.c_str());
+    // Note that CMAKE_GENERATED_FILES is written with a conversion
+    // relative to the home output directory.
     std::string rname =
-      cmSystemTools::RelativePath(dir.c_str(), fname.c_str());
+      cmSystemTools::RelativePath(this->HomeOutputDirectory.c_str(), fname.c_str());
     if(this->FileIsGenerated(rname, scanned, dependencies))
       {
       return true;

Source/cmLocalUnixMakefileGenerator3.cxx

@@ -1275,6 +1275,7 @@ cmLocalUnixMakefileGenerator3
                                includeRegexScan.c_str(),
                                includeRegexComplain.c_str(),
                                generatedFiles, includeCacheFileName);
+      scanner->SetHomeOutputDirectory(mf->GetHomeOutputDirectory());
       }
 #ifdef CMAKE_BUILD_WITH_CMAKE
     else if(lang == "Fortran")