BUG: Avoid dangerous use of putenv

https://stackoverflow.com/a/54279521

While std::getenv is part of the C++ standard, the putenv function isn't.

As you can see from the linked POSIX reference for putenv, it's argument
is of type char *.  This is very important, and one thing that differs
between C and C++: In C a literal string can be passed to functions
expecting char *. In C++ all literal strings are constant and can only
be passed to functions expecting const char *.

Use the itksys::Process::PutEnv wrapper that provides
cross platform safe wrappers for setting/getting
the environmental variables.

Modules/Core/Common/src/itkObjectFactoryBase.cxx

@@ -34,6 +34,7 @@
 #include "itkLightObject.h"
 #include "itkSingleton.h"
 #include "itkVersion.h"
+#include "itksys/SystemTools.hxx"
 #include <cstring>
 #include <algorithm>
 
@@ -305,19 +306,17 @@ ObjectFactoryBase::LoadDynamicFactories()
   char       PathSeparator = ':';
 #  endif
 
-  std::string LoadPath;
-  if (getenv("ITK_AUTOLOAD_PATH"))
-  {
-    LoadPath = getenv("ITK_AUTOLOAD_PATH");
-  }
-  else
+  const std::string itk_autoload_env{ "ITK_AUTOLOAD_PATH" };
+  std::string       LoadPath;
+  if (!itksys::SystemTools::GetEnv(itk_autoload_env, LoadPath))
   {
     return;
   }
   if (LoadPath.empty())
   {
     return;
   }
+
   std::string::size_type EndSeparatorPosition = 0;
   std::string::size_type StartSeparatorPosition = 0;
 

Modules/Core/Common/test/itkObjectFactoryTest2.cxx

@@ -20,6 +20,7 @@
 #include "itkRGBPixel.h"
 #include "itkTextOutput.h" // Needed to see warnings
 #include "itkTestingMacros.h"
+#include "itksys/SystemTools.hxx"
 
 using myPointer = itk::ImportImageContainer<unsigned long, short>::Pointer;
 bool
@@ -118,10 +119,18 @@ itkObjectFactoryTest2(int argc, char * argv[])
 #ifdef CMAKE_INTDIR
   path += std::string("/") + std::string(CMAKE_INTDIR);
 #endif
+  const std::string itk_autoload_env{ "ITK_AUTOLOAD_PATH" };
+  const std::string myenv{ itk_autoload_env + "=" + path };
+  itksys::SystemTools::PutEnv(myenv);
+  std::cout << "SetValue => " << myenv << std::endl;
+  std::string getmyenv;
+  if (!itksys::SystemTools::GetEnv(itk_autoload_env, getmyenv))
+  {
+    std::cerr << "ERROR: Environmental variable not set as requested : " << itk_autoload_env << "!=" << path
+              << std::endl;
+  }
+  std::cout << "GetValue => " << itk_autoload_env + "=" + getmyenv << std::endl;
 
-  std::string myenv = std::string("ITK_AUTOLOAD_PATH=") + path;
-  std::cout << myenv << std::endl;
-  putenv(const_cast<char *>(myenv.c_str()));
   itk::ObjectFactoryBase::ReHash();
 
   // List all registered factories