Accessing member variables within a boost::asio::spawned coroutine - c++

Question

I'm trying to add some async operations deep within an existing codebase, which is being called within a web server implemented using pion (which itself uses boost::asio).
The current code needs to continue operating in contexts where there is no io_service available, so I did the following, where Foo::bar is the main entry point of the existing codebase, and handleRequest is the pion request handler:
class Foo
{
public:
void bar(std::string input, boost::asio::io_service* io = NULL)
{
ioService = io;
if ( io == NULL )
{
barCommon(input);
}
else
{
boost::asio::spawn(*io, boost::bind(&Foo::barAsync, this, input, _1));
}
}
void barAsync(std::string input, boost::asio::yield_context yc)
{
barCommon(input, &yc);
}
void barCommon(std::string input, boost::asio::yield_context* yieldContext = NULL)
{
// Existing code here, with some operations performed async
// using ioService and yieldContext if they are not NULL.
}
private:
boost::asio::io_service* ioService;
// Other member variables, which cause a crash when accessed
}
void handleRequest(pion::http::request_ptr request, pion::tcp::connection_ptr connection)
{
Foo* foo = acquireFooPointer();
foo->bar(std::string(request->get_content()), &connection->get_io_service());
}
This seems to work insofar as it ends up running Foo::barCommon inside a coroutine, but the existing code crashes as soon as it tries to access Foo member variables. What am I missing here?
EDIT: Just to be clear, the pointer acquired in handleRequest is to a heap-allocated Foo object whose lifetime matches that of the server process.