ENH: Introduce "rule hashes" to help rebuild files when rules change.

  - In CMake 2.4 custom commands would not rebuild when rules changed.
  - In CMake 2.6.0 custom commands have a dependency on build.make
    which causes them to rebuild when changed, but also when any
    source is added or removed.  This is too often.
  - We cannot have a per-rule file because Windows filesystems
    do not deal well with lots of small files.
  - Instead we add a persistent CMakeFiles/CMakeRuleHashes.txt file
    at the top of the build tree that is updated during each
    CMake Generate step.  It records a hash of the build rule for
    each file to be built.  When the hash changes the file is
    removed so that it will be rebuilt.

1 files changed, 9 insertions, 0 deletions

diff --git a/Source/cmGlobalGenerator.h b/Source/cmGlobalGenerator.h
index 519158f..ae9a46d 100644
--- a/Source/cmGlobalGenerator.h
+++ b/Source/cmGlobalGenerator.h
@@ -245,6 +245,10 @@ public:
   void FileReplacedDuringGenerate(const std::string& filename);
   void GetFilesReplacedDuringGenerate(std::vector<std::string>& filenames);
 
+  void AddRuleHash(const std::vector<std::string>& outputs,
+                   const std::vector<std::string>& depends,
+                   const std::vector<std::string>& commands);
+
 protected:
   // for a project collect all its targets by following depend
   // information, and also collect all the targets
@@ -313,6 +317,11 @@ private:
   // this is used to improve performance
   std::map<cmStdString,cmTarget *> TotalTargets;
 
+  // Record hashes for rules and outputs.
+  struct RuleHash { char Data[32]; };
+  std::map<cmStdString, RuleHash> RuleHashes;
+  void CheckRuleHashes();
+
   cmExternalMakefileProjectGenerator* ExtraGenerator;
 
   // track files replaced during a Generate