Hi, I'm trying to call my own C function from a small RPython program. When I try to build the program I see this error: [translation:ERROR] Exception: stand-alone program entry point must return an int (and not, e.g., None or always raise an exception). This is the entire RPython program: from rpython.rtyper.lltypesystem import rffi, lltype from rpython.translator.tool.cbuild import ExternalCompilationInfo info = ExternalCompilationInfo(includes=["./myheader.h"], libraries=["./my_functions.so"]) print_thread_mode = rffi.llexternal("print_thread_mode", [lltype.Void], lltype.Void, compilation_info=info) def entry_point(argv): print_thread_mode() return 0 def target(*args): return entry_point The entry_point function is returning an int (0 here). If I remove the call to print_thread_mode() the program compiles. The C function is declared in a .c file. I compiled that file to .so and was able to use it using ctypes in CPython. This is its prototype: void print_thread_mode(void). It simply prints some text. Is there something I am missing?