ENH: Refactor custom command rule hashing

This simplifies computation of custom command rule hashes to hash
content exactly chosen as the custom commands are generated.
Unfortunately this will change the hashes of existing build trees from
earlier CMake versions, but this is not a big deal.  The change is
necessary so that in the future we can make optional adjustments to
custom command lines at generate time without changing the hashes every
time the option is changed.

Source/cmGlobalGenerator.cxx

@@ -2004,8 +2004,7 @@ cmGlobalGenerator::GetDirectoryContent(std::string const& dir, bool needDisk)
 //----------------------------------------------------------------------------
 void
 cmGlobalGenerator::AddRuleHash(const std::vector<std::string>& outputs,
-                               std::vector<std::string>::const_iterator first,
-                               std::vector<std::string>::const_iterator last)
+                               std::string const& content)
 {
 #if defined(CMAKE_BUILD_WITH_CMAKE)
   // Ignore if there are no outputs.
@@ -2017,16 +2016,12 @@ cmGlobalGenerator::AddRuleHash(const std::vector<std::string>& outputs,
   // Compute a hash of the rule.
   RuleHash hash;
   {
-  unsigned char const* data;
-  int length;
+  unsigned char const* data =
+    reinterpret_cast<unsigned char const*>(content.c_str());
+  int length = static_cast<int>(content.length());
   cmsysMD5* sum = cmsysMD5_New();
   cmsysMD5_Initialize(sum);
-  for(std::vector<std::string>::const_iterator i = first; i != last; ++i)
-    {
-    data = reinterpret_cast<unsigned char const*>(i->c_str());
-    length = static_cast<int>(i->length());
-    cmsysMD5_Append(sum, data, length);
-    }
+  cmsysMD5_Append(sum, data, length);
   cmsysMD5_FinalizeHex(sum, hash.Data);
   cmsysMD5_Delete(sum);
   }

Source/cmGlobalGenerator.h

@@ -251,8 +251,7 @@ public:
   void GetFilesReplacedDuringGenerate(std::vector<std::string>& filenames);
 
   void AddRuleHash(const std::vector<std::string>& outputs,
-                   std::vector<std::string>::const_iterator first,
-                   std::vector<std::string>::const_iterator last);
+                   std::string const& content);
 
 protected:
   // for a project collect all its targets by following depend

Source/cmLocalUnixMakefileGenerator3.cxx

@@ -968,7 +968,8 @@ void
 cmLocalUnixMakefileGenerator3
 ::AppendCustomCommand(std::vector<std::string>& commands,
                       const cmCustomCommand& cc, bool echo_comment,
-                      cmLocalGenerator::RelativeRoot relative)
+                      cmLocalGenerator::RelativeRoot relative,
+                      std::ostream* content)
 {
   // Optionally create a command to display the custom command's
   // comment text.  This is used for pre-build, pre-link, and
@@ -991,6 +992,10 @@ cmLocalUnixMakefileGenerator3
     {
     dir = workingDir;
     }
+  if(content)
+    {
+    *content << dir;
+    }
   bool escapeOldStyle = cc.GetEscapeOldStyle();
   bool escapeAllowMakeVars = cc.GetEscapeAllowMakeVars();
 
@@ -1048,6 +1053,10 @@ cmLocalUnixMakefileGenerator3
                                       escapeAllowMakeVars);
           }
         }
+      if(content)
+        {
+        *content << cmd;
+        }
       if(this->BorlandMakeCurlyHack)
         {
         // Borland Make has a very strange bug.  If the first curly

Source/cmLocalUnixMakefileGenerator3.h

@@ -332,7 +332,8 @@ protected:
                            const cmCustomCommand& cc,
                            bool echo_comment=false,
                            cmLocalGenerator::RelativeRoot relative =
-                           cmLocalGenerator::HOME_OUTPUT);
+                           cmLocalGenerator::HOME_OUTPUT,
+                           std::ostream* content = 0);
   void AppendCleanCommand(std::vector<std::string>& commands,
                           const std::vector<std::string>& files,
                           cmTarget& target, const char* filename =0);

Source/cmMakefileTargetGenerator.cxx

@@ -1119,11 +1119,12 @@ void cmMakefileTargetGenerator
       ->AppendEcho(commands, comment.c_str(),
                    cmLocalUnixMakefileGenerator3::EchoGenerate);
     }
-  // Below we need to skip over the echo and progress commands.
-  unsigned int skip = static_cast<unsigned int>(commands.size());
 
   // Now append the actual user-specified commands.
-  this->LocalGenerator->AppendCustomCommand(commands, cc);
+  cmOStringStream content;
+  this->LocalGenerator->AppendCustomCommand(commands, cc, false,
+                                            cmLocalGenerator::HOME_OUTPUT,
+                                            &content);
 
   // Collect the dependencies.
   std::vector<std::string> depends;
@@ -1151,9 +1152,7 @@ void cmMakefileTargetGenerator
   // If the rule has changed make sure the output is rebuilt.
   if(!symbolic)
     {
-    this->GlobalGenerator->AddRuleHash(cc.GetOutputs(),
-                                       commands.begin()+skip,
-                                       commands.end());
+    this->GlobalGenerator->AddRuleHash(cc.GetOutputs(), content.str());
     }
   }