Input Python 3 bytes to C char* via SWIG

You are using multi-argument typemaps wrong. Multi-argument typemaps have to have concrete parameter names. Otherwise they'd match too greedily in situations where this is not desired. To get the bytes and the length of the buffer from Python use PyBytes_AsStringAndSize.\n\ntest.i\n\n\n\n%module example\n%{\nint* swt(char *bytes, int array_length, int width, int height) {\n printf(\"bytes = %s\\narray_length = %d\\nwidth = %d\\nheight = %d\\n\",\n bytes, array_length, width, height);\n return NULL;\n}\n%}\n\n%typemap(in) (char *bytes, int array_length) {\n Py_ssize_t len;\n PyBytes_AsStringAndSize($input, &$1, &len);\n $2 = (int)len;\n}\n\nint* swt(char *bytes, int array_length, int width, int height);\n\n\ntest.py\n\nfrom example import *\nswt(b\"Hello World!\", 100, 50)\n\n\nExample invocation:\n\n$ swig -python -py3 test.i\n$ clang -Wall -Wextra -Wpedantic -I /usr/include/python3.6/ -fPIC -shared test_wrap.c -o _example.so -lpython3.6m\n$ python3 test.py \nbytes = Hello World!\narray_length = 12\nwidth = 100\nheight = 50\n",