ffi

All I want to do is pass a plain-text string from Haskell to C. However, it says that [Char] is an unacceptable return type. I can't find anywhere why they think it is, nor what acceptable return types are. I'm trying to make a very simple OS image that I can boot with Qemu. Does anyone know how to do this? Thanks. {-# LANGUAGE ForeignFunctionInterface #-} module Hello where import Foreign import Foreign.C.String import Foreign.C.Types hello :: String -> (CString -> IO a) -> IO a hello = "Hello, world!" foreign export ccall hello :: String -> (CString -> IO a) -> IO a You want a CString .

I'm working on a Rust wrapper for the Duktape JavaScript interpreter . In a normal use case, the call stack will look like this: Rust: Arbitrary application code. Rust: My library wrapper. C: The Duktape interpreter. Rust: My Rust code. Rust: Arbitrary callbacks into application code. What happens if (5) calls panic! ? According to various Rust developers on IRC, attempting to panic! from inside non-Rust callframes like (3) may result in undefined behavior. But according the Rust documentation, the only way to catch a panic! is using std::task::try , which spawns an extra thread. There's also

I've been learning Rust for about two weeks now and today, I got into its FFI. I used Python to play with Rust, using ctypes and libc. I passed integers, strings and even learned to pass a list of integers ( thanks to this wonderful answer ). Then, I tried to pass a list of strings (following the reasoning behind the that answer), but I failed, as I couldn't get a lead on it. In Python, I have something like this to pass the array of strings. def testRust(): lib = ctypes.cdll.LoadLibrary(rustLib) list_to_send = ['blah', 'blah', 'blah', 'blah'] c_array = (ctypes.c_char_p * len(list_to_send))()

Let's assume we have a C function that takes a set of one or more input arrays, processes them, and writes its output into a set of output arrays. The signature looks as follows (with count representing the number of array elements to be processed): void compute (int count, float** input, float** output) I want to call this function from Python via ctypes and use it to apply a transformation to a set of NumPy arrays. For a one-input/one-output function defined as void compute (int count, float* input, float* output) the following works: import ctypes import numpy from numpy.ctypeslib import

I'm creating an FFI module to a library in C which wants a 1-time, non-reentrant function to be called before anything else is. This call is idempotent, but stateful, so I could just call it in every Haskell call. But it's slow and due to non-reentrancy it could cause conflicts. So is this the right time to use unsafePerformIO? I could wrap a Bool in an unsafe IORef or MVar to make these initialization calls idempotent by ignoring subsequent calls (calls where the global, hidden IORef state is False). If not, what is the right way to do this? Don Stewart I prefer the approach of initializing