7 files changed, 160 insertions, 6 deletions
diff --git a/Source/cmBootstrapCommands.cxx b/Source/cmBootstrapCommands.cxx
index b8031fc..f14b024 100644
--- a/Source/cmBootstrapCommands.cxx
+++ b/Source/cmBootstrapCommands.cxx
@@ -93,6 +93,7 @@
 #include "cmTargetLinkLibrariesCommand.cxx"
 #include "cmTryCompileCommand.cxx"
 #include "cmTryRunCommand.cxx"
+#include "cmUnsetCommand.cxx"
 
 void GetBootstrapCommands(std::list<cmCommand*>& commands)
 {
@@ -163,4 +164,5 @@ void GetBootstrapCommands(std::list<cmCommand*>& commands)
   commands.push_back(new cmTargetLinkLibrariesCommand);
   commands.push_back(new cmTryCompileCommand);
   commands.push_back(new cmTryRunCommand);
+  commands.push_back(new cmUnsetCommand);
 }
diff --git a/Source/cmCacheManager.cxx b/Source/cmCacheManager.cxx
index bd95354..52cb448 100644
--- a/Source/cmCacheManager.cxx
+++ b/Source/cmCacheManager.cxx
@@ -714,10 +714,6 @@ void cmCacheManager::RemoveCacheEntry(const char* key)
     {
     this->Cache.erase(i);
     }
-  else
-    {
-    std::cerr << "Failed to remove entry:" << key << std::endl;
-    }
 }
 
 
diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index 102ca44..a251462 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -1648,6 +1648,11 @@ void cmMakefile::RemoveDefinition(const char* name)
 #endif
 }
 
+void cmMakefile::RemoveCacheDefinition(const char* name)
+{
+  this->GetCacheManager()->RemoveCacheEntry(name);
+}
+
 void cmMakefile::SetProjectName(const char* p)
 {
   this->ProjectName = p;
diff --git a/Source/cmMakefile.h b/Source/cmMakefile.h
index f9d10b6..f78a1dd 100644
--- a/Source/cmMakefile.h
+++ b/Source/cmMakefile.h
@@ -278,6 +278,8 @@ public:
    * for cache entries, and will only affect the current makefile.
    */
   void RemoveDefinition(const char* name);
+  ///! Remove a definition from the cache.
+  void RemoveCacheDefinition(const char* name);
   
   /**
    * Specify the name of the project for this build.
diff --git a/Source/cmSetCommand.h b/Source/cmSetCommand.h
index e818d6a..39d0bc3 100644
--- a/Source/cmSetCommand.h
+++ b/Source/cmSetCommand.h
@@ -87,8 +87,9 @@ public:
       "above the current scope. Each new directory or function creates a new "
       "scope. This command will set the value of a variable into the parent "
       "directory or calling function (whichever is applicable to the case at "
-      "hand) If VALUE is not specified then the variable is removed from the "
-      "parent scope.\n"
+      "hand).\n"
+      "If <value> is not specified then the variable is removed "
+      "instead of set.  See also: the unset() command.\n"
       "  set(<variable> <value1> ... <valueN>)\n"
       "In this case <variable> is set to a semicolon separated list of "
       "values.\n"
diff --git a/Source/cmUnsetCommand.cxx b/Source/cmUnsetCommand.cxx
new file mode 100644
index 0000000..d45b50b
--- /dev/null
+++ b/Source/cmUnsetCommand.cxx
@@ -0,0 +1,64 @@
+/*=========================================================================
+
+  Program:   CMake - Cross-Platform Makefile Generator
+  Module:    $RCSfile$
+  Language:  C++
+  Date:      $Date$
+  Version:   $Revision$
+
+  Copyright (c) 2002 Kitware, Inc., Insight Consortium.  All rights reserved.
+  See Copyright.txt or http://www.cmake.org/HTML/Copyright.html for details.
+
+     This software is distributed WITHOUT ANY WARRANTY; without even
+     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+     PURPOSE.  See the above copyright notices for more information.
+
+=========================================================================*/
+#include "cmUnsetCommand.h"
+
+// cmUnsetCommand
+bool cmUnsetCommand::InitialPass(std::vector<std::string> const& args,
+                                 cmExecutionStatus &)
+{
+  if(args.size() < 1 || args.size() > 2)
+    {
+    this->SetError("called with incorrect number of arguments");
+    return false;
+    }
+
+  const char* variable = args[0].c_str();
+
+  // unset(ENV{VAR})
+  if (!strncmp(variable,"ENV{",4) && strlen(variable) > 5)
+    {
+    // what is the variable name
+    char *envVarName = new char [strlen(variable)];
+    strncpy(envVarName,variable+4,strlen(variable)-5);
+    envVarName[strlen(variable)-5] = '\0';
+
+#ifdef CMAKE_BUILD_WITH_CMAKE
+    cmSystemTools::UnsetEnv(envVarName);
+#endif
+    delete[] envVarName;
+    return true;
+    }
+  // unset(VAR)
+  else if (args.size() == 1)
+    {
+    this->Makefile->RemoveDefinition(variable);
+    return true;
+    }
+  // unset(VAR CACHE)
+  else if ((args.size() == 2) && (args[1] == "CACHE"))
+    {
+    this->Makefile->RemoveCacheDefinition(variable);
+    return true;
+    }
+  // ERROR: second argument isn't CACHE
+  else
+    {
+    this->SetError("called with an invalid second argument");
+    return false;
+    }
+}
+
diff --git a/Source/cmUnsetCommand.h b/Source/cmUnsetCommand.h
new file mode 100644
index 0000000..d125a18
--- /dev/null
+++ b/Source/cmUnsetCommand.h
@@ -0,0 +1,84 @@
+/*=========================================================================
+
+  Program:   CMake - Cross-Platform Makefile Generator
+  Module:    $RCSfile$
+  Language:  C++
+  Date:      $Date$
+  Version:   $Revision$
+
+  Copyright (c) 2002 Kitware, Inc., Insight Consortium.  All rights reserved.
+  See Copyright.txt or http://www.cmake.org/HTML/Copyright.html for details.
+
+     This software is distributed WITHOUT ANY WARRANTY; without even
+     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+     PURPOSE.  See the above copyright notices for more information.
+
+=========================================================================*/
+#ifndef cmUnsetCommand_h
+#define cmUnsetCommand_h
+
+#include "cmCommand.h"
+
+/** \class cmUnsetCommand
+ * \brief Unset a CMAKE variable
+ *
+ * cmUnsetCommand unsets or removes a variable.
+ */
+class cmUnsetCommand : public cmCommand
+{
+public:
+  /**
+   * This is a virtual constructor for the command.
+   */
+  virtual cmCommand* Clone()
+    {
+    return new cmUnsetCommand;
+    }
+
+  /**
+   * This is called when the command is first encountered in
+   * the CMakeLists.txt file.
+   */
+  virtual bool InitialPass(std::vector<std::string> const& args,
+                           cmExecutionStatus &status);
+
+  /**
+   * This determines if the command is invoked when in script mode.
+   */
+  virtual bool IsScriptable() { return true; }
+
+  /**
+   * The name of the command as specified in CMakeList.txt.
+   */
+  virtual const char* GetName() {return "unset";}
+
+  /**
+   * Succinct documentation.
+   */
+  virtual const char* GetTerseDocumentation()
+    {
+    return "Unset a variable, cache variable, or environment variable.";
+    }
+
+  /**
+   * More documentation.
+   */
+  virtual const char* GetFullDocumentation()
+    {
+    return
+      "  unset(<variable> [CACHE])\n"
+      "Removes the specified variable causing it to become undefined.  "
+      "If CACHE is present then the variable is removed from the cache "
+      "instead of the current scope.\n"
+      "<variable> can be an environment variable such as:\n"
+      "  unset(ENV{LD_LIBRARY_PATH})\n"
+      "in which case the variable will be removed from the current "
+      "environment.";
+    }
+
+  cmTypeMacro(cmUnsetCommand, cmCommand);
+};
+
+
+
+#endif