ENH: Add unset() command.

This introduces the unset() command to make it easy to unset CMake
variables, environment variables, and CMake cache variables.  Previously
it was not even possible to unset ENV or CACHE variables (as in
completely remove them).  Changes based on patch from Philip Lowman.
See issue #7507.

1 files changed, 64 insertions, 0 deletions

diff --git a/Source/cmUnsetCommand.cxx b/Source/cmUnsetCommand.cxx
new file mode 100644
index 0000000000..d45b50b55a
--- /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;
+    }
+}
+