1 files changed, 50 insertions, 0 deletions
diff --git a/Source/cmUnsetCommand.cxx b/Source/cmUnsetCommand.cxx
new file mode 100644
index 0000000..cfaa1fd2
--- /dev/null
+++ b/Source/cmUnsetCommand.cxx
@@ -0,0 +1,50 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#include "cmUnsetCommand.h"
+
+#include "cmAlgorithms.h"
+#include "cmMakefile.h"
+#include "cmSystemTools.h"
+
+class cmExecutionStatus;
+
+// cmUnsetCommand
+bool cmUnsetCommand::InitialPass(std::vector<std::string> const& args,
+                                 cmExecutionStatus&)
+{
+  if (args.empty() || args.size() > 2) {
+    this->SetError("called with incorrect number of arguments");
+    return false;
+  }
+
+  auto const& variable = args[0];
+
+  // unset(ENV{VAR})
+  if (cmHasLiteralPrefix(variable, "ENV{") && variable.size() > 5) {
+    // what is the variable name
+    auto const& envVarName = variable.substr(4, variable.size() - 5);
+
+#ifdef CMAKE_BUILD_WITH_CMAKE
+    cmSystemTools::UnsetEnv(envVarName.c_str());
+#endif
+    return true;
+  }
+  // unset(VAR)
+  if (args.size() == 1) {
+    this->Makefile->RemoveDefinition(variable);
+    return true;
+  }
+  // unset(VAR CACHE)
+  if ((args.size() == 2) && (args[1] == "CACHE")) {
+    this->Makefile->RemoveCacheDefinition(variable);
+    return true;
+  }
+  // unset(VAR PARENT_SCOPE)
+  if ((args.size() == 2) && (args[1] == "PARENT_SCOPE")) {
+    this->Makefile->RaiseScope(variable, nullptr);
+    return true;
+  }
+  // ERROR: second argument isn't CACHE or PARENT_SCOPE
+  this->SetError("called with an invalid second argument");
+  return false;
+}