Parser/asdl_c.py

#! /usr/bin/env python
"""Generate C code from an ASDL description."""

import os
import sys
import textwrap

from argparse import ArgumentParser
from pathlib import Path

import asdl

TABSIZE = 4
MAX_COL = 80
AUTOGEN_MESSAGE = "// File automatically generated by {}.\n\n"

def get_c_type(name):
    """Return a string for the C name of the type.

    This function special cases the default types provided by asdl.
    """
    if name in asdl.builtin_types:
        return name
    else:
        return "%s_ty" % name

def reflow_lines(s, depth):
    """Reflow the line s indented depth tabs.

    Return a sequence of lines where no line extends beyond MAX_COL
    when properly indented.  The first line is properly indented based
    exclusively on depth * TABSIZE.  All following lines -- these are
    the reflowed lines generated by this function -- start at the same
    column as the first character beyond the opening { in the first
    line.
    """
    size = MAX_COL - depth * TABSIZE
    if len(s) < size:
        return [s]

    lines = []
    cur = s
    padding = ""
    while len(cur) > size:
        i = cur.rfind(' ', 0, size)
        # XXX this should be fixed for real
        if i == -1 and 'GeneratorExp' in cur:
            i = size + 3
        assert i != -1, "Impossible line %d to reflow: %r" % (size, s)
        lines.append(padding + cur[:i])
        if len(lines) == 1:
            # find new size based on brace
            j = cur.find('{', 0, i)
            if j >= 0:
                j += 2 # account for the brace and the space after it
                size -= j
                padding = " " * j
            else:
                j = cur.find('(', 0, i)
                if j >= 0:
                    j += 1 # account for the paren (no space after it)
                    size -= j
                    padding = " " * j
        cur = cur[i+1:]
    else:
        lines.append(padding + cur)
    return lines

def reflow_c_string(s, depth):
    return '"%s"' % s.replace('\n', '\\n"\n%s"' % (' ' * depth * TABSIZE))

def is_simple(sum):
    """Return True if a sum is a simple.

    A sum is simple if its types have no fields, e.g.
    unaryop = Invert | Not | UAdd | USub
    """
    for t in sum.types:
        if t.fields:
            return False
    return True

def asdl_of(name, obj):
    if isinstance(obj, asdl.Product) or isinstance(obj, asdl.Constructor):
        fields = ", ".join(map(str, obj.fields))
        if fields:
            fields = "({})".format(fields)
        return "{}{}".format(name, fields)
    else:
        if is_simple(obj):
            types = " | ".join(type.name for type in obj.types)
        else:
            sep = "\n{}| ".format(" " * (len(name) + 1))
            types = sep.join(
                asdl_of(type.name, type) for type in obj.types
            )
        return "{} = {}".format(name, types)

class EmitVisitor(asdl.VisitorBase):
    """Visit that emits lines"""

    def __init__(self, file):
        self.file = file
        self.identifiers = set()
        self.singletons = set()
        self.types = set()
        super(EmitVisitor, self).__init__()

    def emit_identifier(self, name):
        self.identifiers.add(str(name))

    def emit_singleton(self, name):
        self.singletons.add(str(name))

    def emit_type(self, name):
        self.types.add(str(name))

    def emit(self, s, depth, reflow=True):
        # XXX reflow long lines?
        if reflow:
            lines = reflow_lines(s, depth)
        else:
            lines = [s]
        for line in lines:
            if line:
                line = (" " * TABSIZE * depth) + line
            self.file.write(line + "\n")


class TypeDefVisitor(EmitVisitor):
    def visitModule(self, mod):
        for dfn in mod.dfns:
            self.visit(dfn)

    def visitType(self, type, depth=0):
        self.visit(type.value, type.name, depth)

    def visitSum(self, sum, name, depth):
        if is_simple(sum):
            self.simple_sum(sum, name, depth)
        else:
            self.sum_with_constructors(sum, name, depth)

    def simple_sum(self, sum, name, depth):
        enum = []
        for i in range(len(sum.types)):
            type = sum.types[i]
            enum.append("%s=%d" % (type.name, i + 1))
        enums = ", ".join(enum)
        ctype = get_c_type(name)
        s = "typedef enum _%s { %s } %s;" % (name, enums, ctype)
        self.emit(s, depth)
        self.emit("", depth)

    def sum_with_constructors(self, sum, name, depth):
        ctype = get_c_type(name)
        s = "typedef struct _%(name)s *%(ctype)s;" % locals()
        self.emit(s, depth)
        self.emit("", depth)

    def visitProduct(self, product, name, depth):
        ctype = get_c_type(name)
        s = "typedef struct _%(name)s *%(ctype)s;" % locals()
        self.emit(s, depth)
        self.emit("", depth)

class SequenceDefVisitor(EmitVisitor):
    def visitModule(self, mod):
        for dfn in mod.dfns:
            self.visit(dfn)

    def visitType(self, type, depth=0):
        self.visit(type.value, type.name, depth)

    def visitSum(self, sum, name, depth):
        if is_simple(sum):
            return
        self.emit_sequence_constructor(name, depth)

    def emit_sequence_constructor(self, name,depth):
        ctype = get_c_type(name)
        self.emit("""\
typedef struct {
    _ASDL_SEQ_HEAD
    %(ctype)s typed_elements[1];
} asdl_%(name)s_seq;""" % locals(), reflow=False, depth=depth)
        self.emit("", depth)
        self.emit("asdl_%(name)s_seq *_Py_asdl_%(name)s_seq_new(Py_ssize_t size, PyArena *arena);" % locals(), depth)
        self.emit("", depth)

    def visitProduct(self, product, name, depth):
        self.emit_sequence_constructor(name, depth)

class StructVisitor(EmitVisitor):
    """Visitor to generate typedefs for AST."""

    def visitModule(self, mod):
        for dfn in mod.dfns:
            self.visit(dfn)

    def visitType(self, type, depth=0):
        self.visit(type.value, type.name, depth)

    def visitSum(self, sum, name, depth):
        if not is_simple(sum):
            self.sum_with_constructors(sum, name, depth)

    def sum_with_constructors(self, sum, name, depth):
        def emit(s, depth=depth):
            self.emit(s % sys._getframe(1).f_locals, depth)
        enum = []
        for i in range(len(sum.types)):
            type = sum.types[i]
            enum.append("%s_kind=%d" % (type.name, i + 1))

        emit("enum _%(name)s_kind {" + ", ".join(enum) + "};")

        emit("struct _%(name)s {")
        emit("enum _%(name)s_kind kind;", depth + 1)
        emit("union {", depth + 1)
        for t in sum.types:
            self.visit(t, depth + 2)
        emit("} v;", depth + 1)
        for field in sum.attributes:
            # rudimentary attribute handling
            type = str(field.type)
            assert type in asdl.builtin_types, type
            emit("%s %s;" % (type, field.name), depth + 1);
        emit("};")
        emit("")

    def visitConstructor(self, cons, depth):
        if cons.fields:
            self.emit("struct {", depth)
            for f in cons.fields:
                self.visit(f, depth + 1)
            self.emit("} %s;" % cons.name, depth)
            self.emit("", depth)

    def visitField(self, field, depth):
        # XXX need to lookup field.type, because it might be something
        # like a builtin...
        ctype = get_c_type(field.type)
        name = field.name
        if field.seq:
            if field.type == 'cmpop':
                self.emit("asdl_int_seq *%(name)s;" % locals(), depth)
            else:
                _type = field.type
                self.emit("asdl_%(_type)s_seq *%(name)s;" % locals(), depth)
        else:
            self.emit("%(ctype)s %(name)s;" % locals(), depth)

    def visitProduct(self, product, name, depth):
        self.emit("struct _%(name)s {" % locals(), depth)
        for f in product.fields:
            self.visit(f, depth + 1)
        for field in product.attributes:
            # rudimentary attribute handling
            type = str(field.type)
            assert type in asdl.builtin_types, type
            self.emit("%s %s;" % (type, field.name), depth + 1);
        self.emit("};", depth)
        self.emit("", depth)


def ast_func_name(name):
    return f"_PyAST_{name}"


class PrototypeVisitor(EmitVisitor):
    """Generate function prototypes for the .h file"""

    def visitModule(self, mod):
        for dfn in mod.dfns:
            self.visit(dfn)

    def visitType(self, type):
        self.visit(type.value, type.name)

    def visitSum(self, sum, name):
        if is_simple(sum):
            pass # XXX
        else:
            for t in sum.types:
                self.visit(t, name, sum.attributes)

    def get_args(self, fields):
        """Return list of C argument into, one for each field.

        Argument info is 3-tuple of a C type, variable name, and flag
        that is true if type can be NULL.
        """
        args = []
        unnamed = {}
        for f in fields:
            if f.name is None:
                name = f.type
                c = unnamed[name] = unnamed.get(name, 0) + 1
                if c > 1:
                    name = "name%d" % (c - 1)
            else:
                name = f.name
            # XXX should extend get_c_type() to handle this
            if f.seq:
                if f.type == 'cmpop':
                    ctype = "asdl_int_seq *"
                else:
                    ctype = f"asdl_{f.type}_seq *"
            else:
                ctype = get_c_type(f.type)
            args.append((ctype, name, f.opt or f.seq))
        return args

    def visitConstructor(self, cons, type, attrs):
        args = self.get_args(cons.fields)
        attrs = self.get_args(attrs)
        ctype = get_c_type(type)
        self.emit_function(cons.name, ctype, args, attrs)

    def emit_function(self, name, ctype, args, attrs, union=True):
        args = args + attrs
        if args:
            argstr = ", ".join(["%s %s" % (atype, aname)
                                for atype, aname, opt in args])
            argstr += ", PyArena *arena"
        else:
            argstr = "PyArena *arena"
        self.emit("%s %s(%s);" % (ctype, ast_func_name(name), argstr), False)

    def visitProduct(self, prod, name):
        self.emit_function(name, get_c_type(name),
                           self.get_args(prod.fields),
                           self.get_args(prod.attributes),
                           union=False)


class FunctionVisitor(PrototypeVisitor):
    """Visitor to generate constructor functions for AST."""

    def emit_function(self, name, ctype, args, attrs, union=True):
        def emit(s, depth=0, reflow=True):
            self.emit(s, depth, reflow)
        argstr = ", ".join(["%s %s" % (atype, aname)
                            for atype, aname, opt in args + attrs])
        if argstr:
            argstr += ", PyArena *arena"
        else:
            argstr = "PyArena *arena"
        self.emit("%s" % ctype, 0)
        emit("%s(%s)" % (ast_func_name(name), argstr))
        emit("{")
        emit("%s p;" % ctype, 1)
        for argtype, argname, opt in args:
            if not opt and argtype != "int":
                emit("if (!%s) {" % argname, 1)
                emit("PyErr_SetString(PyExc_ValueError,", 2)
                msg = "field '%s' is required for %s" % (argname, name)
                emit('                "%s");' % msg,
                     2, reflow=False)
                emit('return NULL;', 2)
                emit('}', 1)

        emit("p = (%s)_PyArena_Malloc(arena, sizeof(*p));" % ctype, 1);
        emit("if (!p)", 1)
        emit("return NULL;", 2)
        if union:
            self.emit_body_union(name, args, attrs)
        else:
            self.emit_body_struct(name, args, attrs)
        emit("return p;", 1)
        emit("}")
        emit("")

    def emit_body_union(self, name, args, attrs):
        def emit(s, depth=0, reflow=True):
            self.emit(s, depth, reflow)
        emit("p->kind = %s_kind;" % name, 1)
        for argtype, argname, opt in args:
            emit("p->v.%s.%s = %s;" % (name, argname, argname), 1)
        for argtype, argname, opt in attrs:
            emit("p->%s = %s;" % (argname, argname), 1)

    def emit_body_struct(self, name, args, attrs):
        def emit(s, depth=0, reflow=True):
            self.emit(s, depth, reflow)
        for argtype, argname, opt in args:
            emit("p->%s = %s;" % (argname, argname), 1)
        for argtype, argname, opt in attrs:
            emit("p->%s = %s;" % (argname, argname), 1)


class PickleVisitor(EmitVisitor):

    def visitModule(self, mod):
        for dfn in mod.dfns:
            self.visit(dfn)

    def visitType(self, type):
        self.visit(type.value, type.name)

    def visitSum(self, sum, name):
        pass

    def visitProduct(self, sum, name):
        pass

    def visitConstructor(self, cons, name):
        pass

    def visitField(self, sum):
        pass


class Obj2ModPrototypeVisitor(PickleVisitor):
    def visitProduct(self, prod, name):
        code = "static int obj2ast_%s(struct ast_state *state, PyObject* obj, %s* out, PyArena* arena);"
        self.emit(code % (name, get_c_type(name)), 0)

    visitSum = visitProduct


class Obj2ModVisitor(PickleVisitor):
    def funcHeader(self, name):
        ctype = get_c_type(name)
        self.emit("int", 0)
        self.emit("obj2ast_%s(struct ast_state *state, PyObject* obj, %s* out, PyArena* arena)" % (name, ctype), 0)
        self.emit("{", 0)
        self.emit("int isinstance;", 1)
        self.emit("", 0)

    def sumTrailer(self, name, add_label=False):
        self.emit("", 0)
        # there's really nothing more we can do if this fails ...
        error = "expected some sort of %s, but got %%R" % name
        format = "PyErr_Format(PyExc_TypeError, \"%s\", obj);"
        self.emit(format % error, 1, reflow=False)
        if add_label:
            self.emit("failed:", 1)
            self.emit("Py_XDECREF(tmp);", 1)
        self.emit("return 1;", 1)
        self.emit("}", 0)
        self.emit("", 0)

    def simpleSum(self, sum, name):
        self.funcHeader(name)
        for t in sum.types:
            line = ("isinstance = PyObject_IsInstance(obj, "
                    "state->%s_type);")
            self.emit(line % (t.name,), 1)
            self.emit("if (isinstance == -1) {", 1)
            self.emit("return 1;", 2)
            self.emit("}", 1)
            self.emit("if (isinstance) {", 1)
            self.emit("*out = %s;" % t.name, 2)
            self.emit("return 0;", 2)
            self.emit("}", 1)
        self.sumTrailer(name)

    def buildArgs(self, fields):
        return ", ".join(fields + ["arena"])

    def complexSum(self, sum, name):
        self.funcHeader(name)
        self.emit("PyObject *tmp = NULL;", 1)
        self.emit("PyObject *tp;", 1)
        for a in sum.attributes:
            self.visitAttributeDeclaration(a, name, sum=sum)
        self.emit("", 0)
        # XXX: should we only do this for 'expr'?
        self.emit("if (obj == Py_None) {", 1)
        self.emit("*out = NULL;", 2)
        self.emit("return 0;", 2)
        self.emit("}", 1)
        for a in sum.attributes:
            self.visitField(a, name, sum=sum, depth=1)
        for t in sum.types:
            self.emit("tp = state->%s_type;" % (t.name,), 1)
            self.emit("isinstance = PyObject_IsInstance(obj, tp);", 1)
            self.emit("if (isinstance == -1) {", 1)
            self.emit("return 1;", 2)
            self.emit("}", 1)
            self.emit("if (isinstance) {", 1)
            for f in t.fields:
                self.visitFieldDeclaration(f, t.name, sum=sum, depth=2)
            self.emit("", 0)
            for f in t.fields:
                self.visitField(f, t.name, sum=sum, depth=2)
            args = [f.name for f in t.fields] + [a.name for a in sum.attributes]
            self.emit("*out = %s(%s);" % (ast_func_name(t.name), self.buildArgs(args)), 2)
            self.emit("if (*out == NULL) goto failed;", 2)
            self.emit("return 0;", 2)
            self.emit("}", 1)
        self.sumTrailer(name, True)

    def visitAttributeDeclaration(self, a, name, sum=sum):
        ctype = get_c_type(a.type)
        self.emit("%s %s;" % (ctype, a.name), 1)

    def visitSum(self, sum, name):
        if is_simple(sum):
            self.simpleSum(sum, name)
        else:
            self.complexSum(sum, name)

    def visitProduct(self, prod, name):
        ctype = get_c_type(name)
        self.emit("int", 0)
        self.emit("obj2ast_%s(struct ast_state *state, PyObject* obj, %s* out, PyArena* arena)" % (name, ctype), 0)
        self.emit("{", 0)
        self.emit("PyObject* tmp = NULL;", 1)
        for f in prod.fields:
            self.visitFieldDeclaration(f, name, prod=prod, depth=1)
        for a in prod.attributes:
            self.visitFieldDeclaration(a, name, prod=prod, depth=1)
        self.emit("", 0)
        for f in prod.fields:
            self.visitField(f, name, prod=prod, depth=1)
        for a in prod.attributes:
            self.visitField(a, name, prod=prod, depth=1)
        args = [f.name for f in prod.fields]
        args.extend([a.name for a in prod.attributes])
        self.emit("*out = %s(%s);" % (ast_func_name(name), self.buildArgs(args)), 1)
        self.emit("return 0;", 1)
        self.emit("failed:", 0)
        self.emit("Py_XDECREF(tmp);", 1)
        self.emit("return 1;", 1)
        self.emit("}", 0)
        self.emit("", 0)

    def visitFieldDeclaration(self, field, name, sum=None, prod=None, depth=0):
        ctype = get_c_type(field.type)
        if field.seq:
            if self.isSimpleType(field):
                self.emit("asdl_int_seq* %s;" % field.name, depth)
            else:
                _type = field.type
                self.emit(f"asdl_{field.type}_seq* {field.name};", depth)
        else:
            ctype = get_c_type(field.type)
            self.emit("%s %s;" % (ctype, field.name), depth)

    def isSimpleSum(self, field):
        # XXX can the members of this list be determined automatically?
        return field.type in ('expr_context', 'boolop', 'operator',
                              'unaryop', 'cmpop')

    def isNumeric(self, field):
        return get_c_type(field.type) in ("int", "bool")

    def isSimpleType(self, field):
        return self.isSimpleSum(field) or self.isNumeric(field)

    def visitField(self, field, name, sum=None, prod=None, depth=0):
        ctype = get_c_type(field.type)
        line = "if (_PyObject_LookupAttr(obj, state->%s, &tmp) < 0) {"
        self.emit(line % field.name, depth)
        self.emit("return 1;", depth+1)
        self.emit("}", depth)
        if not field.opt:
            self.emit("if (tmp == NULL) {", depth)
            message = "required field \\\"%s\\\" missing from %s" % (field.name, name)
            format = "PyErr_SetString(PyExc_TypeError, \"%s\");"
            self.emit(format % message, depth+1, reflow=False)
            self.emit("return 1;", depth+1)
        else:
            self.emit("if (tmp == NULL || tmp == Py_None) {", depth)
            self.emit("Py_CLEAR(tmp);", depth+1)
            if self.isNumeric(field):
                self.emit("%s = 0;" % field.name, depth+1)
            elif not self.isSimpleType(field):
                self.emit("%s = NULL;" % field.name, depth+1)
            else:
                raise TypeError("could not determine the default value for %s" % field.name)
        self.emit("}", depth)
        self.emit("else {", depth)

        self.emit("int res;", depth+1)
        if field.seq:
            self.emit("Py_ssize_t len;", depth+1)
            self.emit("Py_ssize_t i;", depth+1)
            self.emit("if (!PyList_Check(tmp)) {", depth+1)
            self.emit("PyErr_Format(PyExc_TypeError, \"%s field \\\"%s\\\" must "
                      "be a list, not a %%.200s\", _PyType_Name(Py_TYPE(tmp)));" %
                      (name, field.name),
                      depth+2, reflow=False)
            self.emit("goto failed;", depth+2)
            self.emit("}", depth+1)
            self.emit("len = PyList_GET_SIZE(tmp);", depth+1)
            if self.isSimpleType(field):
                self.emit("%s = _Py_asdl_int_seq_new(len, arena);" % field.name, depth+1)
            else:
                self.emit("%s = _Py_asdl_%s_seq_new(len, arena);" % (field.name, field.type), depth+1)
            self.emit("if (%s == NULL) goto failed;" % field.name, depth+1)
            self.emit("for (i = 0; i < len; i++) {", depth+1)
            self.emit("%s val;" % ctype, depth+2)
            self.emit("PyObject *tmp2 = PyList_GET_ITEM(tmp, i);", depth+2)
            self.emit("Py_INCREF(tmp2);", depth+2)
            self.emit("res = obj2ast_%s(state, tmp2, &val, arena);" %
                      field.type, depth+2, reflow=False)
            self.emit("Py_DECREF(tmp2);", depth+2)
            self.emit("if (res != 0) goto failed;", depth+2)
            self.emit("if (len != PyList_GET_SIZE(tmp)) {", depth+2)
            self.emit("PyErr_SetString(PyExc_RuntimeError, \"%s field \\\"%s\\\" "
                      "changed size during iteration\");" %
                      (name, field.name),
                      depth+3, reflow=False)
            self.emit("goto failed;", depth+3)
            self.emit("}", depth+2)
            self.emit("asdl_seq_SET(%s, i, val);" % field.name, depth+2)
            self.emit("}", depth+1)
        else:
            self.emit("res = obj2ast_%s(state, tmp, &%s, arena);" %
                      (field.type, field.name), depth+1)
            self.emit("if (res != 0) goto failed;", depth+1)

        self.emit("Py_CLEAR(tmp);", depth+1)
        self.emit("}", depth)


class SequenceConstructorVisitor(EmitVisitor):
    def visitModule(self, mod):
        for dfn in mod.dfns:
            self.visit(dfn)

    def visitType(self, type):
        self.visit(type.value, type.name)

    def visitProduct(self, prod, name):
        self.emit_sequence_constructor(name, get_c_type(name))

    def visitSum(self, sum, name):
        if not is_simple(sum):
            self.emit_sequence_constructor(name, get_c_type(name))

    def emit_sequence_constructor(self, name, type):
        self.emit(f"GENERATE_ASDL_SEQ_CONSTRUCTOR({name}, {type})", depth=0)

class PyTypesDeclareVisitor(PickleVisitor):

    def visitProduct(self, prod, name):
        self.emit_type("%s_type" % name)
        self.emit("static PyObject* ast2obj_%s(struct ast_state *state, void*);" % name, 0)
        if prod.attributes:
            for a in prod.attributes:
                self.emit_identifier(a.name)
            self.emit("static const char * const %s_attributes[] = {" % name, 0)
            for a in prod.attributes:
                self.emit('"%s",' % a.name, 1)
            self.emit("};", 0)
        if prod.fields:
            for f in prod.fields:
                self.emit_identifier(f.name)
            self.emit("static const char * const %s_fields[]={" % name,0)
            for f in prod.fields:
                self.emit('"%s",' % f.name, 1)
            self.emit("};", 0)

    def visitSum(self, sum, name):
        self.emit_type("%s_type" % name)
        if sum.attributes:
            for a in sum.attributes:
                self.emit_identifier(a.name)
            self.emit("static const char * const %s_attributes[] = {" % name, 0)
            for a in sum.attributes:
                self.emit('"%s",' % a.name, 1)
            self.emit("};", 0)
        ptype = "void*"
        if is_simple(sum):
            ptype = get_c_type(name)
            for t in sum.types:
                self.emit_singleton("%s_singleton" % t.name)
        self.emit("static PyObject* ast2obj_%s(struct ast_state *state, %s);" % (name, ptype), 0)
        for t in sum.types:
            self.visitConstructor(t, name)

    def visitConstructor(self, cons, name):
        if cons.fields:
            for t in cons.fields:
                self.emit_identifier(t.name)
            self.emit("static const char * const %s_fields[]={" % cons.name, 0)
            for t in cons.fields:
                self.emit('"%s",' % t.name, 1)
            self.emit("};",0)


class PyTypesVisitor(PickleVisitor):

    def visitModule(self, mod):
        self.emit("""

typedef struct {
    PyObject_HEAD
    PyObject *dict;
} AST_object;

static void
ast_dealloc(AST_object *self)
{
    /* bpo-31095: UnTrack is needed before calling any callbacks */
    PyTypeObject *tp = Py_TYPE(self);
    PyObject_GC_UnTrack(self);
    Py_CLEAR(self->dict);
    freefunc free_func = PyType_GetSlot(tp, Py_tp_free);
    assert(free_func != NULL);
    free_func(self);
    Py_DECREF(tp);
}

static int
ast_traverse(AST_object *self, visitproc visit, void *arg)
{
    Py_VISIT(Py_TYPE(self));
    Py_VISIT(self->dict);
    return 0;
}

static int
ast_clear(AST_object *self)
{
    Py_CLEAR(self->dict);
    return 0;
}

static int
ast_type_init(PyObject *self, PyObject *args, PyObject *kw)
{
    struct ast_state *state = get_ast_state();
    if (state == NULL) {
        return -1;
    }

    Py_ssize_t i, numfields = 0;
    int res = -1;
    PyObject *key, *value, *fields;
    if (_PyObject_LookupAttr((PyObject*)Py_TYPE(self), state->_fields, &fields) < 0) {
        goto cleanup;
    }
    if (fields) {
        numfields = PySequence_Size(fields);
        if (numfields == -1) {
            goto cleanup;
        }
    }

    res = 0; /* if no error occurs, this stays 0 to the end */
    if (numfields < PyTuple_GET_SIZE(args)) {
        PyErr_Format(PyExc_TypeError, "%.400s constructor takes at most "
                     "%zd positional argument%s",
                     _PyType_Name(Py_TYPE(self)),
                     numfields, numfields == 1 ? "" : "s");
        res = -1;
        goto cleanup;
    }
    for (i = 0; i < PyTuple_GET_SIZE(args); i++) {
        /* cannot be reached when fields is NULL */
        PyObject *name = PySequence_GetItem(fields, i);
        if (!name) {
            res = -1;
            goto cleanup;
        }
        res = PyObject_SetAttr(self, name, PyTuple_GET_ITEM(args, i));
        Py_DECREF(name);
        if (res < 0) {
            goto cleanup;
        }
    }
    if (kw) {
        i = 0;  /* needed by PyDict_Next */
        while (PyDict_Next(kw, &i, &key, &value)) {
            int contains = PySequence_Contains(fields, key);
            if (contains == -1) {
                res = -1;
                goto cleanup;
            } else if (contains == 1) {
                Py_ssize_t p = PySequence_Index(fields, key);
                if (p == -1) {
                    res = -1;
                    goto cleanup;
                }
                if (p < PyTuple_GET_SIZE(args)) {
                    PyErr_Format(PyExc_TypeError,
                        "%.400s got multiple values for argument '%U'",
                        Py_TYPE(self)->tp_name, key);
                    res = -1;
                    goto cleanup;
                }
            }
            res = PyObject_SetAttr(self, key, value);
            if (res < 0) {
                goto cleanup;
            }
        }
    }
  cleanup:
    Py_XDECREF(fields);
    return res;
}

/* Pickling support */
static PyObject *
ast_type_reduce(PyObject *self, PyObject *unused)
{
    struct ast_state *state = get_ast_state();
    if (state == NULL) {
        return NULL;
    }

    PyObject *dict;
    if (_PyObject_LookupAttr(self, state->__dict__, &dict) < 0) {
        return NULL;
    }
    if (dict) {
        return Py_BuildValue("O()N", Py_TYPE(self), dict);
    }
    return Py_BuildValue("O()", Py_TYPE(self));
}

static PyMemberDef ast_type_members[] = {
    {"__dictoffset__", T_PYSSIZET, offsetof(AST_object, dict), READONLY},
    {NULL}  /* Sentinel */
};

static PyMethodDef ast_type_methods[] = {
    {"__reduce__", ast_type_reduce, METH_NOARGS, NULL},
    {NULL}
};

static PyGetSetDef ast_type_getsets[] = {
    {"__dict__", PyObject_GenericGetDict, PyObject_GenericSetDict},
    {NULL}
};

static PyType_Slot AST_type_slots[] = {
    {Py_tp_dealloc, ast_dealloc},
    {Py_tp_getattro, PyObject_GenericGetAttr},
    {Py_tp_setattro, PyObject_GenericSetAttr},
    {Py_tp_traverse, ast_traverse},
    {Py_tp_clear, ast_clear},
    {Py_tp_members, ast_type_members},
    {Py_tp_methods, ast_type_methods},
    {Py_tp_getset, ast_type_getsets},
    {Py_tp_init, ast_type_init},
    {Py_tp_alloc, PyType_GenericAlloc},
    {Py_tp_new, PyType_GenericNew},
    {Py_tp_free, PyObject_GC_Del},
    {0, 0},
};

static PyType_Spec AST_type_spec = {
    "ast.AST",
    sizeof(AST_object),
    0,
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
    AST_type_slots
};

static PyObject *
make_type(struct ast_state *state, const char *type, PyObject* base,
          const char* const* fields, int num_fields, const char *doc)
{
    PyObject *fnames, *result;
    int i;
    fnames = PyTuple_New(num_fields);
    if (!fnames) return NULL;
    for (i = 0; i < num_fields; i++) {
        PyObject *field = PyUnicode_InternFromString(fields[i]);
        if (!field) {
            Py_DECREF(fnames);
            return NULL;
        }
        PyTuple_SET_ITEM(fnames, i, field);
    }
    result = PyObject_CallFunction((PyObject*)&PyType_Type, "s(O){OOOOOOOs}",
                    type, base,
                    state->_fields, fnames,
                    state->__match_args__, fnames,
                    state->__module__,
                    state->ast,
                    state->__doc__, doc);
    Py_DECREF(fnames);
    return result;
}

static int
add_attributes(struct ast_state *state, PyObject *type, const char * const *attrs, int num_fields)
{
    int i, result;
    PyObject *s, *l = PyTuple_New(num_fields);
    if (!l)
        return 0;
    for (i = 0; i < num_fields; i++) {
        s = PyUnicode_InternFromString(attrs[i]);
        if (!s) {
            Py_DECREF(l);
            return 0;
        }
        PyTuple_SET_ITEM(l, i, s);
    }
    result = PyObject_SetAttr(type, state->_attributes, l) >= 0;
    Py_DECREF(l);
    return result;
}

/* Conversion AST -> Python */

static PyObject* ast2obj_list(struct ast_state *state, asdl_seq *seq, PyObject* (*func)(struct ast_state *state, void*))
{
    Py_ssize_t i, n = asdl_seq_LEN(seq);
    PyObject *result = PyList_New(n);
    PyObject *value;
    if (!result)
        return NULL;
    for (i = 0; i < n; i++) {
        value = func(state, asdl_seq_GET_UNTYPED(seq, i));
        if (!value) {
            Py_DECREF(result);
            return NULL;
        }
        PyList_SET_ITEM(result, i, value);
    }
    return result;
}

static PyObject* ast2obj_object(struct ast_state *Py_UNUSED(state), void *o)
{
    if (!o)
        o = Py_None;
    Py_INCREF((PyObject*)o);
    return (PyObject*)o;
}
#define ast2obj_constant ast2obj_object
#define ast2obj_identifier ast2obj_object
#define ast2obj_string ast2obj_object

static PyObject* ast2obj_int(struct ast_state *Py_UNUSED(state), long b)
{
    return PyLong_FromLong(b);
}

/* Conversion Python -> AST */

static int obj2ast_object(struct ast_state *Py_UNUSED(state), PyObject* obj, PyObject** out, PyArena* arena)
{
    if (obj == Py_None)
        obj = NULL;
    if (obj) {
        if (_PyArena_AddPyObject(arena, obj) < 0) {
            *out = NULL;
            return -1;
        }
        Py_INCREF(obj);
    }
    *out = obj;
    return 0;
}

static int obj2ast_constant(struct ast_state *Py_UNUSED(state), PyObject* obj, PyObject** out, PyArena* arena)
{
    if (_PyArena_AddPyObject(arena, obj) < 0) {
        *out = NULL;
        return -1;
    }
    Py_INCREF(obj);
    *out = obj;
    return 0;
}

static int obj2ast_identifier(struct ast_state *state, PyObject* obj, PyObject** out, PyArena* arena)
{
    if (!PyUnicode_CheckExact(obj) && obj != Py_None) {
        PyErr_SetString(PyExc_TypeError, "AST identifier must be of type str");
        return 1;
    }
    return obj2ast_object(state, obj, out, arena);
}

static int obj2ast_string(struct ast_state *state, PyObject* obj, PyObject** out, PyArena* arena)
{
    if (!PyUnicode_CheckExact(obj) && !PyBytes_CheckExact(obj)) {
        PyErr_SetString(PyExc_TypeError, "AST string must be of type str");
        return 1;
    }
    return obj2ast_object(state, obj, out, arena);
}

static int obj2ast_int(struct ast_state* Py_UNUSED(state), PyObject* obj, int* out, PyArena* arena)
{
    int i;
    if (!PyLong_Check(obj)) {
        PyErr_Format(PyExc_ValueError, "invalid integer value: %R", obj);
        return 1;
    }

    i = _PyLong_AsInt(obj);
    if (i == -1 && PyErr_Occurred())
        return 1;
    *out = i;
    return 0;
}

static int add_ast_fields(struct ast_state *state)
{
    PyObject *empty_tuple;
    empty_tuple = PyTuple_New(0);
    if (!empty_tuple ||
        PyObject_SetAttrString(state->AST_type, "_fields", empty_tuple) < 0 ||
        PyObject_SetAttrString(state->AST_type, "__match_args__", empty_tuple) < 0 ||
        PyObject_SetAttrString(state->AST_type, "_attributes", empty_tuple) < 0) {
        Py_XDECREF(empty_tuple);
        return -1;
    }
    Py_DECREF(empty_tuple);
    return 0;
}

""", 0, reflow=False)

        self.file.write(textwrap.dedent('''
            static int
            init_types(struct ast_state *state)
            {
                // init_types() must not be called after _PyAST_Fini()
                // has been called
                assert(state->initialized >= 0);

                if (state->initialized) {
                    return 1;
                }
                if (init_identifiers(state) < 0) {
                    return 0;
                }
                state->AST_type = PyType_FromSpec(&AST_type_spec);
                if (!state->AST_type) {
                    return 0;
                }
                if (add_ast_fields(state) < 0) {
                    return 0;
                }
        '''))
        for dfn in mod.dfns:
            self.visit(dfn)
        self.file.write(textwrap.dedent('''
                state->initialized = 1;
                return 1;
            }
        '''))

    def visitProduct(self, prod, name):
        if prod.fields:
            fields = name+"_fields"
        else:
            fields = "NULL"
        self.emit('state->%s_type = make_type(state, "%s", state->AST_type, %s, %d,' %
                        (name, name, fields, len(prod.fields)), 1)
        self.emit('%s);' % reflow_c_string(asdl_of(name, prod), 2), 2, reflow=False)
        self.emit("if (!state->%s_type) return 0;" % name, 1)
        self.emit_type("AST_type")
        self.emit_type("%s_type" % name)
        if prod.attributes:
            self.emit("if (!add_attributes(state, state->%s_type, %s_attributes, %d)) return 0;" %
                            (name, name, len(prod.attributes)), 1)
        else:
            self.emit("if (!add_attributes(state, state->%s_type, NULL, 0)) return 0;" % name, 1)
        self.emit_defaults(name, prod.fields, 1)
        self.emit_defaults(name, prod.attributes, 1)

    def visitSum(self, sum, name):
        self.emit('state->%s_type = make_type(state, "%s", state->AST_type, NULL, 0,' %
                  (name, name), 1)
        self.emit('%s);' % reflow_c_string(asdl_of(name, sum), 2), 2, reflow=False)
        self.emit_type("%s_type" % name)
        self.emit("if (!state->%s_type) return 0;" % name, 1)
        if sum.attributes:
            self.emit("if (!add_attributes(state, state->%s_type, %s_attributes, %d)) return 0;" %
                            (name, name, len(sum.attributes)), 1)
        else:
            self.emit("if (!add_attributes(state, state->%s_type, NULL, 0)) return 0;" % name, 1)
        self.emit_defaults(name, sum.attributes, 1)
        simple = is_simple(sum)
        for t in sum.types:
            self.visitConstructor(t, name, simple)

    def visitConstructor(self, cons, name, simple):
        if cons.fields:
            fields = cons.name+"_fields"
        else:
            fields = "NULL"
        self.emit('state->%s_type = make_type(state, "%s", state->%s_type, %s, %d,' %
                            (cons.name, cons.name, name, fields, len(cons.fields)), 1)
        self.emit('%s);' % reflow_c_string(asdl_of(cons.name, cons), 2), 2, reflow=False)
        self.emit("if (!state->%s_type) return 0;" % cons.name, 1)
        self.emit_type("%s_type" % cons.name)
        self.emit_defaults(cons.name, cons.fields, 1)
        if simple:
            self.emit("state->%s_singleton = PyType_GenericNew((PyTypeObject *)"
                      "state->%s_type, NULL, NULL);" %
                             (cons.name, cons.name), 1)
            self.emit("if (!state->%s_singleton) return 0;" % cons.name, 1)

    def emit_defaults(self, name, fields, depth):
        for field in fields:
            if field.opt:
                self.emit('if (PyObject_SetAttr(state->%s_type, state->%s, Py_None) == -1)' %
                            (name, field.name), depth)
                self.emit("return 0;", depth+1)


class ASTModuleVisitor(PickleVisitor):

    def visitModule(self, mod):
        self.emit("static int", 0)
        self.emit("astmodule_exec(PyObject *m)", 0)
        self.emit("{", 0)
        self.emit('struct ast_state *state = get_ast_state();', 1)
        self.emit('if (state == NULL) {', 1)
        self.emit('return -1;', 2)
        self.emit('}', 1)
        self.emit('if (PyModule_AddObjectRef(m, "AST", state->AST_type) < 0) {', 1)
        self.emit('return -1;', 2)
        self.emit('}', 1)
        self.emit('if (PyModule_AddIntMacro(m, PyCF_ALLOW_TOP_LEVEL_AWAIT) < 0) {', 1)
        self.emit("return -1;", 2)
        self.emit('}', 1)
        self.emit('if (PyModule_AddIntMacro(m, PyCF_ONLY_AST) < 0) {', 1)
        self.emit("return -1;", 2)
        self.emit('}', 1)
        self.emit('if (PyModule_AddIntMacro(m, PyCF_TYPE_COMMENTS) < 0) {', 1)
        self.emit("return -1;", 2)
        self.emit('}', 1)
        for dfn in mod.dfns:
            self.visit(dfn)
        self.emit("return 0;", 1)
        self.emit("}", 0)
        self.emit("", 0)
        self.emit("""
static PyModuleDef_Slot astmodule_slots[] = {
    {Py_mod_exec, astmodule_exec},
    {0, NULL}
};

static struct PyModuleDef _astmodule = {
    PyModuleDef_HEAD_INIT,
    .m_name = "_ast",
    // The _ast module uses a per-interpreter state (PyInterpreterState.ast)
    .m_size = 0,
    .m_slots = astmodule_slots,
};

PyMODINIT_FUNC
PyInit__ast(void)
{
    return PyModuleDef_Init(&_astmodule);
}
""".strip(), 0, reflow=False)

    def visitProduct(self, prod, name):
        self.addObj(name)

    def visitSum(self, sum, name):
        self.addObj(name)
        for t in sum.types:
            self.visitConstructor(t, name)

    def visitConstructor(self, cons, name):
        self.addObj(cons.name)

    def addObj(self, name):
        self.emit("if (PyModule_AddObjectRef(m, \"%s\", "
                  "state->%s_type) < 0) {" % (name, name), 1)
        self.emit("return -1;", 2)
        self.emit('}', 1)


class StaticVisitor(PickleVisitor):
    CODE = '''Very simple, always emit this static code.  Override CODE'''

    def visit(self, object):
        self.emit(self.CODE, 0, reflow=False)


class ObjVisitor(PickleVisitor):

    def func_begin(self, name):
        ctype = get_c_type(name)
        self.emit("PyObject*", 0)
        self.emit("ast2obj_%s(struct ast_state *state, void* _o)" % (name), 0)
        self.emit("{", 0)
        self.emit("%s o = (%s)_o;" % (ctype, ctype), 1)
        self.emit("PyObject *result = NULL, *value = NULL;", 1)
        self.emit("PyTypeObject *tp;", 1)
        self.emit('if (!o) {', 1)
        self.emit("Py_RETURN_NONE;", 2)
        self.emit("}", 1)

    def func_end(self):
        self.emit("return result;", 1)
        self.emit("failed:", 0)
        self.emit("Py_XDECREF(value);", 1)
        self.emit("Py_XDECREF(result);", 1)
        self.emit("return NULL;", 1)
        self.emit("}", 0)
        self.emit("", 0)

    def visitSum(self, sum, name):
        if is_simple(sum):
            self.simpleSum(sum, name)
            return
        self.func_begin(name)
        self.emit("switch (o->kind) {", 1)
        for i in range(len(sum.types)):
            t = sum.types[i]
            self.visitConstructor(t, i + 1, name)
        self.emit("}", 1)
        for a in sum.attributes:
            self.emit("value = ast2obj_%s(state, o->%s);" % (a.type, a.name), 1)
            self.emit("if (!value) goto failed;", 1)
            self.emit('if (PyObject_SetAttr(result, state->%s, value) < 0)' % a.name, 1)
            self.emit('goto failed;', 2)
            self.emit('Py_DECREF(value);', 1)
        self.func_end()

    def simpleSum(self, sum, name):
        self.emit("PyObject* ast2obj_%s(struct ast_state *state, %s_ty o)" % (name, name), 0)
        self.emit("{", 0)
        self.emit("switch(o) {", 1)
        for t in sum.types:
            self.emit("case %s:" % t.name, 2)
            self.emit("Py_INCREF(state->%s_singleton);" % t.name, 3)
            self.emit("return state->%s_singleton;" % t.name, 3)
        self.emit("}", 1)
        self.emit("Py_UNREACHABLE();", 1);
        self.emit("}", 0)

    def visitProduct(self, prod, name):
        self.func_begin(name)
        self.emit("tp = (PyTypeObject *)state->%s_type;" % name, 1)
        self.emit("result = PyType_GenericNew(tp, NULL, NULL);", 1);
        self.emit("if (!result) return NULL;", 1)
        for field in prod.fields:
            self.visitField(field, name, 1, True)
        for a in prod.attributes:
            self.emit("value = ast2obj_%s(state, o->%s);" % (a.type, a.name), 1)
            self.emit("if (!value) goto failed;", 1)
            self.emit("if (PyObject_SetAttr(result, state->%s, value) < 0)" % a.name, 1)
            self.emit('goto failed;', 2)
            self.emit('Py_DECREF(value);', 1)
        self.func_end()

    def visitConstructor(self, cons, enum, name):
        self.emit("case %s_kind:" % cons.name, 1)
        self.emit("tp = (PyTypeObject *)state->%s_type;" % cons.name, 2)
        self.emit("result = PyType_GenericNew(tp, NULL, NULL);", 2);
        self.emit("if (!result) goto failed;", 2)
        for f in cons.fields:
            self.visitField(f, cons.name, 2, False)
        self.emit("break;", 2)

    def visitField(self, field, name, depth, product):
        def emit(s, d):
            self.emit(s, depth + d)
        if product:
            value = "o->%s" % field.name
        else:
            value = "o->v.%s.%s" % (name, field.name)
        self.set(field, value, depth)
        emit("if (!value) goto failed;", 0)
        emit("if (PyObject_SetAttr(result, state->%s, value) == -1)" % field.name, 0)
        emit("goto failed;", 1)
        emit("Py_DECREF(value);", 0)

    def set(self, field, value, depth):
        if field.seq:
            # XXX should really check for is_simple, but that requires a symbol table
            if field.type == "cmpop":
                # While the sequence elements are stored as void*,
                # ast2obj_cmpop expects an enum
                self.emit("{", depth)
                self.emit("Py_ssize_t i, n = asdl_seq_LEN(%s);" % value, depth+1)
                self.emit("value = PyList_New(n);", depth+1)
                self.emit("if (!value) goto failed;", depth+1)
                self.emit("for(i = 0; i < n; i++)", depth+1)
                # This cannot fail, so no need for error handling
                self.emit("PyList_SET_ITEM(value, i, ast2obj_cmpop(state, (cmpop_ty)asdl_seq_GET(%s, i)));" % value,
                          depth+2, reflow=False)
                self.emit("}", depth)
            else:
                self.emit("value = ast2obj_list(state, (asdl_seq*)%s, ast2obj_%s);" % (value, field.type), depth)
        else:
            self.emit("value = ast2obj_%s(state, %s);" % (field.type, value), depth, reflow=False)


class PartingShots(StaticVisitor):

    CODE = """
PyObject* PyAST_mod2obj(mod_ty t)
{
    struct ast_state *state = get_ast_state();
    if (state == NULL) {
        return NULL;
    }
    return ast2obj_mod(state, t);
}

/* mode is 0 for "exec", 1 for "eval" and 2 for "single" input */
mod_ty PyAST_obj2mod(PyObject* ast, PyArena* arena, int mode)
{
    const char * const req_name[] = {"Module", "Expression", "Interactive"};
    int isinstance;

    if (PySys_Audit("compile", "OO", ast, Py_None) < 0) {
        return NULL;
    }

    struct ast_state *state = get_ast_state();
    if (state == NULL) {
        return NULL;
    }

    PyObject *req_type[3];
    req_type[0] = state->Module_type;
    req_type[1] = state->Expression_type;
    req_type[2] = state->Interactive_type;

    assert(0 <= mode && mode <= 2);

    isinstance = PyObject_IsInstance(ast, req_type[mode]);
    if (isinstance == -1)
        return NULL;
    if (!isinstance) {
        PyErr_Format(PyExc_TypeError, "expected %s node, got %.400s",
                     req_name[mode], _PyType_Name(Py_TYPE(ast)));
        return NULL;
    }

    mod_ty res = NULL;
    if (obj2ast_mod(state, ast, &res, arena) != 0)
        return NULL;
    else
        return res;
}

int PyAST_Check(PyObject* obj)
{
    struct ast_state *state = get_ast_state();
    if (state == NULL) {
        return -1;
    }
    return PyObject_IsInstance(obj, state->AST_type);
}
"""

class ChainOfVisitors:
    def __init__(self, *visitors):
        self.visitors = visitors

    def visit(self, object):
        for v in self.visitors:
            v.visit(object)
            v.emit("", 0)


def generate_ast_state(module_state, f):
    f.write('struct ast_state {\n')
    f.write('    int initialized;\n')
    for s in module_state:
        f.write('    PyObject *' + s + ';\n')
    f.write('};')


def generate_ast_fini(module_state, f):
    f.write(textwrap.dedent("""
            void _PyAST_Fini(PyInterpreterState *interp)
            {
                struct ast_state *state = &interp->ast;

    """))
    for s in module_state:
        f.write("    Py_CLEAR(state->" + s + ');\n')
    f.write(textwrap.dedent("""
            #if !defined(NDEBUG)
                state->initialized = -1;
            #else
                state->initialized = 0;
            #endif
            }

    """))


def generate_module_def(mod, f, internal_h):
    # Gather all the data needed for ModuleSpec
    visitor_list = set()
    with open(os.devnull, "w") as devnull:
        visitor = PyTypesDeclareVisitor(devnull)
        visitor.visit(mod)
        visitor_list.add(visitor)
        visitor = PyTypesVisitor(devnull)
        visitor.visit(mod)
        visitor_list.add(visitor)

    state_strings = {
        "ast",
        "_fields",
        "__match_args__",
        "__doc__",
        "__dict__",
        "__module__",
        "_attributes",
    }
    module_state = state_strings.copy()
    for visitor in visitor_list:
        for identifier in visitor.identifiers:
            module_state.add(identifier)
            state_strings.add(identifier)
        for singleton in visitor.singletons:
            module_state.add(singleton)
        for tp in visitor.types:
            module_state.add(tp)
    state_strings = sorted(state_strings)
    module_state = sorted(module_state)

    generate_ast_state(module_state, internal_h)

    print(textwrap.dedent("""
        #include "Python.h"
        #include "pycore_ast.h"
        #include "pycore_ast_state.h"       // struct ast_state
        #include "pycore_interp.h"          // _PyInterpreterState.ast
        #include "pycore_pystate.h"         // _PyInterpreterState_GET()
        #include "structmember.h"
        #include <stddef.h>

        // Forward declaration
        static int init_types(struct ast_state *state);

        static struct ast_state*
        get_ast_state(void)
        {
            PyInterpreterState *interp = _PyInterpreterState_GET();
            struct ast_state *state = &interp->ast;
            if (!init_types(state)) {
                return NULL;
            }
            return state;
        }
    """).strip(), file=f)

    generate_ast_fini(module_state, f)

    f.write('static int init_identifiers(struct ast_state *state)\n')
    f.write('{\n')
    for identifier in state_strings:
        f.write('    if ((state->' + identifier)
        f.write(' = PyUnicode_InternFromString("')
        f.write(identifier + '")) == NULL) return 0;\n')
    f.write('    return 1;\n')
    f.write('};\n\n')

def write_header(mod, f):
    f.write(textwrap.dedent("""
        #ifndef Py_INTERNAL_AST_H
        #define Py_INTERNAL_AST_H
        #ifdef __cplusplus
        extern "C" {
        #endif

        #ifndef Py_BUILD_CORE
        #  error "this header requires Py_BUILD_CORE define"
        #endif

        #include "pycore_asdl.h"

    """).lstrip())
    c = ChainOfVisitors(TypeDefVisitor(f),
                        SequenceDefVisitor(f),
                        StructVisitor(f))
    c.visit(mod)
    f.write("// Note: these macros affect function definitions, not only call sites.\n")
    PrototypeVisitor(f).visit(mod)
    f.write(textwrap.dedent("""

        PyObject* PyAST_mod2obj(mod_ty t);
        mod_ty PyAST_obj2mod(PyObject* ast, PyArena* arena, int mode);
        int PyAST_Check(PyObject* obj);

        extern int _PyAST_Validate(mod_ty);

        /* _PyAST_ExprAsUnicode is defined in ast_unparse.c */
        extern PyObject* _PyAST_ExprAsUnicode(expr_ty);

        /* Return the borrowed reference to the first literal string in the
           sequence of statements or NULL if it doesn't start from a literal string.
           Doesn't set exception. */
        extern PyObject* _PyAST_GetDocString(asdl_stmt_seq *);

        #ifdef __cplusplus
        }
        #endif
        #endif /* !Py_INTERNAL_AST_H */
    """))


def write_internal_h_header(mod, f):
    print(textwrap.dedent("""
        #ifndef Py_INTERNAL_AST_STATE_H
        #define Py_INTERNAL_AST_STATE_H
        #ifdef __cplusplus
        extern "C" {
        #endif

        #ifndef Py_BUILD_CORE
        #  error "this header requires Py_BUILD_CORE define"
        #endif
    """).lstrip(), file=f)


def write_internal_h_footer(mod, f):
    print(textwrap.dedent("""

        #ifdef __cplusplus
        }
        #endif
        #endif /* !Py_INTERNAL_AST_STATE_H */
    """), file=f)


def write_source(mod, f, internal_h_file):
    generate_module_def(mod, f, internal_h_file)

    v = ChainOfVisitors(
        SequenceConstructorVisitor(f),
        PyTypesDeclareVisitor(f),
        PyTypesVisitor(f),
        Obj2ModPrototypeVisitor(f),
        FunctionVisitor(f),
        ObjVisitor(f),
        Obj2ModVisitor(f),
        ASTModuleVisitor(f),
        PartingShots(f),
    )
    v.visit(mod)

def main(input_filename, c_filename, h_filename, internal_h_filename, dump_module=False):
    auto_gen_msg = AUTOGEN_MESSAGE.format("/".join(Path(__file__).parts[-2:]))
    mod = asdl.parse(input_filename)
    if dump_module:
        print('Parsed Module:')
        print(mod)
    if not asdl.check(mod):
        sys.exit(1)

    with c_filename.open("w") as c_file, \
         h_filename.open("w") as h_file, \
         internal_h_filename.open("w") as internal_h_file:
        c_file.write(auto_gen_msg)
        h_file.write(auto_gen_msg)
        internal_h_file.write(auto_gen_msg)

        write_internal_h_header(mod, internal_h_file)
        write_source(mod, c_file, internal_h_file)
        write_header(mod, h_file)
        write_internal_h_footer(mod, internal_h_file)

    print(f"{c_filename}, {h_filename}, {internal_h_filename} regenerated.")

if __name__ == "__main__":
    parser = ArgumentParser()
    parser.add_argument("input_file", type=Path)
    parser.add_argument("-C", "--c-file", type=Path, required=True)
    parser.add_argument("-H", "--h-file", type=Path, required=True)
    parser.add_argument("-I", "--internal-h-file", type=Path, required=True)
    parser.add_argument("-d", "--dump-module", action="store_true")

    args = parser.parse_args()
    main(args.input_file, args.c_file, args.h_file,
         args.internal_h_file, args.dump_module)