René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Incorrect marshalling of string in Py_SetPythonHome","articleBody":"I noticed that when `PythonEngine.PythonHome` was set and a subsequent `Initialize()` call was made my .Net application would close unexpectedly.\n\nIt looks like the call to `Py_SetPythonHome` made in runtime.cs is implicitly marshalling the string to a char array for the unmanaged code. My suspicion is that the Python sourcecode is keeping a record of the pointer rather than making a copy of the data. The managed runtime will free the memory allocated to char array as soon as the function finishes executing leaving a dangling pointer. This then leads to the unexpected `Initialize()` behaviour.\n\n```\n[DllImport(Runtime.dll, CallingConvention = CallingConvention.Cdecl,\n    ExactSpelling = true, CharSet = CharSet.Ansi)]\ninternal unsafe static extern void\nPy_SetPythonHome(string home);\n```\n\nThe solution appears to be to explicitly marshal the string and hang onto the pointer until it is no longer needed, i.e.\n\n```\n[DllImport(Runtime.dll, CallingConvention = CallingConvention.Cdecl,\n     ExactSpelling = true, CharSet = CharSet.Ansi)]\ninternal unsafe static extern void\nPy_SetPythonHome(IntPtr home);\n```\n\n```\nIntPtr str = Marshal.StringToHGlobalAnsi(@\"C:\\Python27\");\nPy_SetPythonHome(str);\n// do stuff\nMarshal.FreeHGlobal(str);\n```\n\nRunning Win7, .Net4.5 and Python 2.7.11.\n","author":{"url":"https://github.com/leomeuk","@type":"Person","name":"leomeuk"},"datePublished":"2016-03-08T21:09:23.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/179/pythonnet/issues/179"}