Python C API from LLVM IR

foo.ll

%struct.pyobject = type { i32, i8* }

@hello = private unnamed_addr constant [16 x i8] c"Hello From LLVM\00", align 1
@empty = private unnamed_addr constant [1 x i8] c"\00", align 1

declare void @puts(i8*)
declare %struct.pyobject* @PyObject_CallFunction(%struct.pyobject*, i8*, ...)
declare %struct.pyobject* @PyObject_Repr(%struct.pyobject*)

define %struct.pyobject* @try_this(%struct.pyobject* %arg) {
    ; Say hello from LLVM land
    call void (i8*)* @puts(i8* getelementptr inbounds ([16 x i8]* @hello, i32 0, i32 0))

    ; Return value is the repr() of the argument.
    %ret = call %struct.pyobject* (%struct.pyobject*)* @PyObject_Repr(%struct.pyobject* %arg)

    ; Can't do this yet since we need an LLVM version of Py_DECREF to use
    ; on the result.
    ; %dummy = call %struct.pyobject* (%struct.pyobject*, i8*, ...)* @PyObject_CallFunction(%struct.pyobject* %arg, i8* null)

    ret %struct.pyobject* %ret
}

Makefile

libfoo.so: foo.o
	gcc foo.o -shared -o libfoo.so

foo.o: foo.ll
	llc-3.3 -filetype=obj -relocation-model=pic foo.ll

trycall.py

import ctypes

def baz():
    print "Hello from back in Python land"

module = ctypes.cdll.LoadLibrary("./libtryllvm.so")
func = module.try_this
func.restype = ctypes.py_object
func.argtypes = (ctypes.py_object,)
# FIXME: Why does it segfault if we pass a list in here?
result = func(baz)

print repr(result)