cmPropertyMap: Introduce cmProp as return type for GetProperty() functions

Currently properties are usually stored internally as `std::string`.
However, family of GetProperty() functions return them as `const char *` using `c_str()`.
The proposed `cmProp`, typedef'ed as `const std::string *` will expose properties
more naturally.

1 files changed, 3 insertions, 2 deletions

diff --git a/Source/cmTest.cxx b/Source/cmTest.cxx
index 3b731cc..56c441a 100644
--- a/Source/cmTest.cxx
+++ b/Source/cmTest.cxx
@@ -34,15 +34,16 @@ void cmTest::SetCommand(std::vector<std::string> const& command)
 
 const char* cmTest::GetProperty(const std::string& prop) const
 {
-  const char* retVal = this->Properties.GetPropertyValue(prop);
+  cmProp retVal = this->Properties.GetPropertyValue(prop);
   if (!retVal) {
     const bool chain =
       this->Makefile->GetState()->IsPropertyChained(prop, cmProperty::TEST);
     if (chain) {
       return this->Makefile->GetProperty(prop, chain);
     }
+    return nullptr;
   }
-  return retVal;
+  return retVal->c_str();
 }
 
 bool cmTest::GetPropertyAsBool(const std::string& prop) const