Port to Python 3

[nodeg]

First attempt to port twopence to Python 3. Fixes #69.

TODO

• replace removed PyFile_Check
• Fix compiler warnings regarding the port:

$ make

make -C python all
cc -fPIC -I/usr/local/opt/python@3.9/Frameworks/Python.framework/Versions/3.9/include/python3.9 -I../library -Wall -O2 -g3   -c -o extension.o extension.c
extension.c:175:1: warning: non-void function does not return a value [-Wreturn-type]
}                                                                                                                                                               
^                                                                               
1 warning generated.                                                            
cc -fPIC -I/usr/local/opt/python@3.9/Frameworks/Python.framework/Versions/3.9/include/python3.9 -I../library -Wall -O2 -g3   -c -o command.o command.c
command.c:80:2: warning: suggest braces around initialization of subobject [-Wmissing-braces]
        PyObject_HEAD_INIT(NULL)                                                
        ^~~~~~~~~~~~~~~~~~~~~~~~ 
/usr/local/opt/python@3.9/Frameworks/Python.framework/Versions/3.9/include/python3.9/object.h:86:5: note: expanded from macro 'PyObject_HEAD_INIT'
    1, type },         
    ^~~~~~~                                                                                                                                                     
command.c:194:10: warning: assigning to 'char *' from 'const char *' discards qualifiers [-Wincompatible-pointer-types-discards-qualifiers]
                if ((s = PyUnicode_AsUTF8(stdinObject)) == NULL)
                       ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
command.c:248:6: error: implicit declaration of function 'PyFile_Check' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        if (PyFile_Check(object)) {
            ^
command.c:333:6: warning: incompatible pointer types assigning to 'FILE *' (aka 'struct __sFILE *') from 'PyObject *' (aka 'struct _object *') [-Wincompatible-p
ointer-types]
                fp = PySys_GetObject("stdin");
                   ^ ~~~~~~~~~~~~~~~~~~~~~~~~
command.c:435:28: warning: incompatible integer to pointer conversion passing 'long' to parameter of type 'const char *' [-Wint-conversion]
                return PyLong_FromString(self->timeout, NULL, 0);
                                         ^~~~~~~~~~~~~
/usr/local/opt/python@3.9/Frameworks/Python.framework/Versions/3.9/include/python3.9/longobject.h:103:54: note: passing argument to parameter here
PyAPI_FUNC(PyObject *) PyLong_FromString(const char *, char **, int);
                                                     ^
command.c:441:28: warning: incompatible integer to pointer conversion passing 'unsigned int' to parameter of type 'const char *' [-Wint-conversion]
                return PyLong_FromString(self->pid, NULL, 0);
                                        ^~~~~~~~~
/usr/local/opt/python@3.9/Frameworks/Python.framework/Versions/3.9/include/python3.9/longobject.h:103:54: note: passing argument to parameter here
PyAPI_FUNC(PyObject *) PyLong_FromString(const char *, char **, int);
                                                     ^
command.c:474:33: warning: incompatible pointer types passing 'twopence_Command *' to parameter of type 'PyObject *' (aka 'struct _object *') [-Wincompatible-po
inter-types]
        return PyObject_GenericGetAttr(self, PyUnicode_FromString(name));
                                       ^~~~
/usr/local/opt/python@3.9/Frameworks/Python.framework/Versions/3.9/include/python3.9/object.h:254:58: note: passing argument to parameter here
PyAPI_FUNC(PyObject *) PyObject_GenericGetAttr(PyObject *, PyObject *);
                                                         ^
command.c:495:33: warning: assigning to 'char *' from 'const char *' discards qualifiers [-Wincompatible-pointer-types-discards-qualifiers]
                if (!PyUnicode_Check(v) || (s = PyUnicode_AsUTF8(v)) == NULL)
                                              ^ ~~~~~~~~~~~~~~~~~~~
7 warnings and 1 error generated.
make[1]: *** [command.o] Error 1
make: *** [all] Error 1

Links

• https://py3c.readthedocs.io/en/latest/fileshim.html
• https://docs.python.org/3.3/c-api/file.html