The following message is a courtesy copy of an article that has been posted to comp.lang.lisp as well.

Sohail Somani sohail@taggedtype.net writes:

How can I get Slime to relay the output (through std::cout) of a C++ function called through CFFI through to the REPL?

This is really a CFFI question, and you may wish to send further followups to the CFFI list instead. Create a C++ shared library with a few elements, then load and initialize it using CFFI:

1. A subclass of std::ostream that holds a void(*)(const char*) as an instance variable, forwarding all output received to that function.

2. A function like

extern "C" void init_mylispcout (void (*writer) (const char*));

that replaces std::cout with an instance of #1. I forget whether C++ allows you to change std::cout.

3. A CFFI callback in Lisp to be passed to #2, that writes the output on some Lisp stream.

4. A CFFI defcfun on #2.