[C++-sig] runtime error R6025 - pure virtual function call

[Maximilian Wilson]

On 1/25/07, Dave Wolfe <dwolfe at gforcetech.com> wrote:
> // File: main.cpp
> ICallable* CreatePythonHelloPrinter(std::string greetee)
> {
>     ICallable* retval = NULL;
>     try
>     {
>         bpl::object main = bpl::import("__main__");
>         bpl::object global = main.attr("__dict__");
>         bpl::exec_file("pyhello.py", global, global);
>         bpl::object PyHelloPrinter = global["PyHelloPrinter"];
>         bpl::object myPyPrinter = PyHelloPrinter(greetee);
>         retval = bpl::extract<ICallable*>(myPyPrinter);
>     }
>     catch (bpl::error_already_set const&)
>     {
>         std::cerr << GetPythonException();
>     }
>
>     return retval;
> }

I'm no expert on bpl, but are you sure this isn't a dangling pointer?
The bpl::object myPyPrinter goes out of scope when you exit the try
block, which presumably destroys whatever ICallable retval is pointing
to. Thus, when you call pyGreeter->operator()(), you're calling a
method on an object which no longer exists and thus invoking undefined
behavior, so literally anything can happen. To solve this,
CreatePythonHelloPrinter() could return a bpl::object instead of an
ICallable*, and you'd do the extract<> call in main().

-Max Wilson

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