xref: /openbmc/qemu/scripts/qapi/common.py (revision 0ced9531f17c1c28fa4f29b352729c7f40c2ae30)

#
# QAPI helper library
#
# Copyright IBM, Corp. 2011
# Copyright (c) 2013-2018 Red Hat Inc.
#
# Authors:
#  Anthony Liguori <aliguori@us.ibm.com>
#  Markus Armbruster <armbru@redhat.com>
#
# This work is licensed under the terms of the GNU GPL, version 2.
# See the COPYING file in the top-level directory.

from __future__ import print_function
from contextlib import contextmanager
import errno
import os
import re
import string
import sys
from collections import OrderedDict

builtin_types = {
    'null':     'QTYPE_QNULL',
    'str':      'QTYPE_QSTRING',
    'int':      'QTYPE_QNUM',
    'number':   'QTYPE_QNUM',
    'bool':     'QTYPE_QBOOL',
    'int8':     'QTYPE_QNUM',
    'int16':    'QTYPE_QNUM',
    'int32':    'QTYPE_QNUM',
    'int64':    'QTYPE_QNUM',
    'uint8':    'QTYPE_QNUM',
    'uint16':   'QTYPE_QNUM',
    'uint32':   'QTYPE_QNUM',
    'uint64':   'QTYPE_QNUM',
    'size':     'QTYPE_QNUM',
    'any':      None,           # any QType possible, actually
    'QType':    'QTYPE_QSTRING',
}

# Are documentation comments required?
doc_required = False

# Whitelist of commands allowed to return a non-dictionary
returns_whitelist = []

# Whitelist of entities allowed to violate case conventions
name_case_whitelist = []

enum_types = {}
struct_types = {}
union_types = {}
all_names = {}

#
# Parsing the schema into expressions
#


def error_path(parent):
    res = ''
    while parent:
        res = ('In file included from %s:%d:\n' % (parent['file'],
                                                   parent['line'])) + res
        parent = parent['parent']
    return res


class QAPIError(Exception):
    def __init__(self, fname, line, col, incl_info, msg):
        Exception.__init__(self)
        self.fname = fname
        self.line = line
        self.col = col
        self.info = incl_info
        self.msg = msg

    def __str__(self):
        loc = '%s:%d' % (self.fname, self.line)
        if self.col is not None:
            loc += ':%s' % self.col
        return error_path(self.info) + '%s: %s' % (loc, self.msg)


class QAPIParseError(QAPIError):
    def __init__(self, parser, msg):
        col = 1
        for ch in parser.src[parser.line_pos:parser.pos]:
            if ch == '\t':
                col = (col + 7) % 8 + 1
            else:
                col += 1
        QAPIError.__init__(self, parser.fname, parser.line, col,
                           parser.incl_info, msg)


class QAPISemError(QAPIError):
    def __init__(self, info, msg):
        QAPIError.__init__(self, info['file'], info['line'], None,
                           info['parent'], msg)


class QAPIDoc(object):
    """
    A documentation comment block, either expression or free-form

    Expression documentation blocks consist of

    * a body section: one line naming the expression, followed by an
      overview (any number of lines)

    * argument sections: a description of each argument (for commands
      and events) or member (for structs, unions and alternates)

    * features sections: a description of each feature flag

    * additional (non-argument) sections, possibly tagged

    Free-form documentation blocks consist only of a body section.
    """

    class Section(object):
        def __init__(self, name=None):
            # optional section name (argument/member or section name)
            self.name = name
            # the list of lines for this section
            self.text = ''

        def append(self, line):
            self.text += line.rstrip() + '\n'

    class ArgSection(Section):
        def __init__(self, name):
            QAPIDoc.Section.__init__(self, name)
            self.member = None

        def connect(self, member):
            self.member = member

    def __init__(self, parser, info):
        # self._parser is used to report errors with QAPIParseError.  The
        # resulting error position depends on the state of the parser.
        # It happens to be the beginning of the comment.  More or less
        # servicable, but action at a distance.
        self._parser = parser
        self.info = info
        self.symbol = None
        self.body = QAPIDoc.Section()
        # dict mapping parameter name to ArgSection
        self.args = OrderedDict()
        self.features = OrderedDict()
        # a list of Section
        self.sections = []
        # the current section
        self._section = self.body
        self._append_line = self._append_body_line

    def has_section(self, name):
        """Return True if we have a section with this name."""
        for i in self.sections:
            if i.name == name:
                return True
        return False

    def append(self, line):
        """
        Parse a comment line and add it to the documentation.

        The way that the line is dealt with depends on which part of
        the documentation we're parsing right now:
        * The body section: ._append_line is ._append_body_line
        * An argument section: ._append_line is ._append_args_line
        * A features section: ._append_line is ._append_features_line
        * An additional section: ._append_line is ._append_various_line
        """
        line = line[1:]
        if not line:
            self._append_freeform(line)
            return

        if line[0] != ' ':
            raise QAPIParseError(self._parser, "Missing space after #")
        line = line[1:]
        self._append_line(line)

    def end_comment(self):
        self._end_section()

    @staticmethod
    def _is_section_tag(name):
        return name in ('Returns:', 'Since:',
                        # those are often singular or plural
                        'Note:', 'Notes:',
                        'Example:', 'Examples:',
                        'TODO:')

    def _append_body_line(self, line):
        """
        Process a line of documentation text in the body section.

        If this a symbol line and it is the section's first line, this
        is an expression documentation block for that symbol.

        If it's an expression documentation block, another symbol line
        begins the argument section for the argument named by it, and
        a section tag begins an additional section.  Start that
        section and append the line to it.

        Else, append the line to the current section.
        """
        name = line.split(' ', 1)[0]
        # FIXME not nice: things like '#  @foo:' and '# @foo: ' aren't
        # recognized, and get silently treated as ordinary text
        if not self.symbol and not self.body.text and line.startswith('@'):
            if not line.endswith(':'):
                raise QAPIParseError(self._parser, "Line should end with :")
            self.symbol = line[1:-1]
            # FIXME invalid names other than the empty string aren't flagged
            if not self.symbol:
                raise QAPIParseError(self._parser, "Invalid name")
        elif self.symbol:
            # This is an expression documentation block
            if name.startswith('@') and name.endswith(':'):
                self._append_line = self._append_args_line
                self._append_args_line(line)
            elif line == 'Features:':
                self._append_line = self._append_features_line
            elif self._is_section_tag(name):
                self._append_line = self._append_various_line
                self._append_various_line(line)
            else:
                self._append_freeform(line.strip())
        else:
            # This is a free-form documentation block
            self._append_freeform(line.strip())

    def _append_args_line(self, line):
        """
        Process a line of documentation text in an argument section.

        A symbol line begins the next argument section, a section tag
        section or a non-indented line after a blank line begins an
        additional section.  Start that section and append the line to
        it.

        Else, append the line to the current section.

        """
        name = line.split(' ', 1)[0]

        if name.startswith('@') and name.endswith(':'):
            line = line[len(name)+1:]
            self._start_args_section(name[1:-1])
        elif self._is_section_tag(name):
            self._append_line = self._append_various_line
            self._append_various_line(line)
            return
        elif (self._section.text.endswith('\n\n')
              and line and not line[0].isspace()):
            if line == 'Features:':
                self._append_line = self._append_features_line
            else:
                self._start_section()
                self._append_line = self._append_various_line
                self._append_various_line(line)
            return

        self._append_freeform(line.strip())

    def _append_features_line(self, line):
        name = line.split(' ', 1)[0]

        if name.startswith('@') and name.endswith(':'):
            line = line[len(name)+1:]
            self._start_features_section(name[1:-1])
        elif self._is_section_tag(name):
            self._append_line = self._append_various_line
            self._append_various_line(line)
            return
        elif (self._section.text.endswith('\n\n')
              and line and not line[0].isspace()):
            self._start_section()
            self._append_line = self._append_various_line
            self._append_various_line(line)
            return

        self._append_freeform(line.strip())

    def _append_various_line(self, line):
        """
        Process a line of documentation text in an additional section.

        A symbol line is an error.

        A section tag begins an additional section.  Start that
        section and append the line to it.

        Else, append the line to the current section.
        """
        name = line.split(' ', 1)[0]

        if name.startswith('@') and name.endswith(':'):
            raise QAPIParseError(self._parser,
                                 "'%s' can't follow '%s' section"
                                 % (name, self.sections[0].name))
        elif self._is_section_tag(name):
            line = line[len(name)+1:]
            self._start_section(name[:-1])

        if (not self._section.name or
                not self._section.name.startswith('Example')):
            line = line.strip()

        self._append_freeform(line)

    def _start_symbol_section(self, symbols_dict, name):
        # FIXME invalid names other than the empty string aren't flagged
        if not name:
            raise QAPIParseError(self._parser, "Invalid parameter name")
        if name in symbols_dict:
            raise QAPIParseError(self._parser,
                                 "'%s' parameter name duplicated" % name)
        assert not self.sections
        self._end_section()
        self._section = QAPIDoc.ArgSection(name)
        symbols_dict[name] = self._section

    def _start_args_section(self, name):
        self._start_symbol_section(self.args, name)

    def _start_features_section(self, name):
        self._start_symbol_section(self.features, name)

    def _start_section(self, name=None):
        if name in ('Returns', 'Since') and self.has_section(name):
            raise QAPIParseError(self._parser,
                                 "Duplicated '%s' section" % name)
        self._end_section()
        self._section = QAPIDoc.Section(name)
        self.sections.append(self._section)

    def _end_section(self):
        if self._section:
            text = self._section.text = self._section.text.strip()
            if self._section.name and (not text or text.isspace()):
                raise QAPIParseError(self._parser, "Empty doc section '%s'"
                                     % self._section.name)
            self._section = None

    def _append_freeform(self, line):
        match = re.match(r'(@\S+:)', line)
        if match:
            raise QAPIParseError(self._parser,
                                 "'%s' not allowed in free-form documentation"
                                 % match.group(1))
        self._section.append(line)

    def connect_member(self, member):
        if member.name not in self.args:
            # Undocumented TODO outlaw
            self.args[member.name] = QAPIDoc.ArgSection(member.name)
        self.args[member.name].connect(member)

    def check_expr(self, expr):
        if self.has_section('Returns') and 'command' not in expr:
            raise QAPISemError(self.info,
                               "'Returns:' is only valid for commands")

    def check(self):
        bogus = [name for name, section in self.args.items()
                 if not section.member]
        if bogus:
            raise QAPISemError(
                self.info,
                "The following documented members are not in "
                "the declaration: %s" % ", ".join(bogus))


class QAPISchemaParser(object):

    def __init__(self, fp, previously_included=[], incl_info=None):
        self.fname = fp.name
        previously_included.append(os.path.abspath(fp.name))
        self.incl_info = incl_info
        self.src = fp.read()
        if self.src == '' or self.src[-1] != '\n':
            self.src += '\n'
        self.cursor = 0
        self.line = 1
        self.line_pos = 0
        self.exprs = []
        self.docs = []
        self.accept()
        cur_doc = None

        while self.tok is not None:
            info = {'file': self.fname, 'line': self.line,
                    'parent': self.incl_info}
            if self.tok == '#':
                self.reject_expr_doc(cur_doc)
                cur_doc = self.get_doc(info)
                self.docs.append(cur_doc)
                continue

            expr = self.get_expr(False)
            if 'include' in expr:
                self.reject_expr_doc(cur_doc)
                if len(expr) != 1:
                    raise QAPISemError(info, "Invalid 'include' directive")
                include = expr['include']
                if not isinstance(include, str):
                    raise QAPISemError(info,
                                       "Value of 'include' must be a string")
                incl_fname = os.path.join(os.path.dirname(self.fname),
                                          include)
                self.exprs.append({'expr': {'include': incl_fname},
                                   'info': info})
                exprs_include = self._include(include, info, incl_fname,
                                              previously_included)
                if exprs_include:
                    self.exprs.extend(exprs_include.exprs)
                    self.docs.extend(exprs_include.docs)
            elif "pragma" in expr:
                self.reject_expr_doc(cur_doc)
                if len(expr) != 1:
                    raise QAPISemError(info, "Invalid 'pragma' directive")
                pragma = expr['pragma']
                if not isinstance(pragma, dict):
                    raise QAPISemError(
                        info, "Value of 'pragma' must be a dictionary")
                for name, value in pragma.items():
                    self._pragma(name, value, info)
            else:
                expr_elem = {'expr': expr,
                             'info': info}
                if cur_doc:
                    if not cur_doc.symbol:
                        raise QAPISemError(
                            cur_doc.info, "Expression documentation required")
                    expr_elem['doc'] = cur_doc
                self.exprs.append(expr_elem)
            cur_doc = None
        self.reject_expr_doc(cur_doc)

    @staticmethod
    def reject_expr_doc(doc):
        if doc and doc.symbol:
            raise QAPISemError(
                doc.info,
                "Documentation for '%s' is not followed by the definition"
                % doc.symbol)

    def _include(self, include, info, incl_fname, previously_included):
        incl_abs_fname = os.path.abspath(incl_fname)
        # catch inclusion cycle
        inf = info
        while inf:
            if incl_abs_fname == os.path.abspath(inf['file']):
                raise QAPISemError(info, "Inclusion loop for %s" % include)
            inf = inf['parent']

        # skip multiple include of the same file
        if incl_abs_fname in previously_included:
            return None

        try:
            if sys.version_info[0] >= 3:
                fobj = open(incl_fname, 'r', encoding='utf-8')
            else:
                fobj = open(incl_fname, 'r')
        except IOError as e:
            raise QAPISemError(info, '%s: %s' % (e.strerror, incl_fname))
        return QAPISchemaParser(fobj, previously_included, info)

    def _pragma(self, name, value, info):
        global doc_required, returns_whitelist, name_case_whitelist
        if name == 'doc-required':
            if not isinstance(value, bool):
                raise QAPISemError(info,
                                   "Pragma 'doc-required' must be boolean")
            doc_required = value
        elif name == 'returns-whitelist':
            if (not isinstance(value, list)
                    or any([not isinstance(elt, str) for elt in value])):
                raise QAPISemError(info,
                                   "Pragma returns-whitelist must be"
                                   " a list of strings")
            returns_whitelist = value
        elif name == 'name-case-whitelist':
            if (not isinstance(value, list)
                    or any([not isinstance(elt, str) for elt in value])):
                raise QAPISemError(info,
                                   "Pragma name-case-whitelist must be"
                                   " a list of strings")
            name_case_whitelist = value
        else:
            raise QAPISemError(info, "Unknown pragma '%s'" % name)

    def accept(self, skip_comment=True):
        while True:
            self.tok = self.src[self.cursor]
            self.pos = self.cursor
            self.cursor += 1
            self.val = None

            if self.tok == '#':
                if self.src[self.cursor] == '#':
                    # Start of doc comment
                    skip_comment = False
                self.cursor = self.src.find('\n', self.cursor)
                if not skip_comment:
                    self.val = self.src[self.pos:self.cursor]
                    return
            elif self.tok in '{}:,[]':
                return
            elif self.tok == "'":
                # Note: we accept only printable ASCII
                string = ''
                esc = False
                while True:
                    ch = self.src[self.cursor]
                    self.cursor += 1
                    if ch == '\n':
                        raise QAPIParseError(self, 'Missing terminating "\'"')
                    if esc:
                        # Note: we recognize only \\ because we have
                        # no use for funny characters in strings
                        if ch != '\\':
                            raise QAPIParseError(self,
                                                 "Unknown escape \\%s" % ch)
                        esc = False
                    elif ch == '\\':
                        esc = True
                        continue
                    elif ch == "'":
                        self.val = string
                        return
                    if ord(ch) < 32 or ord(ch) >= 127:
                        raise QAPIParseError(
                            self, "Funny character in string")
                    string += ch
            elif self.src.startswith('true', self.pos):
                self.val = True
                self.cursor += 3
                return
            elif self.src.startswith('false', self.pos):
                self.val = False
                self.cursor += 4
                return
            elif self.src.startswith('null', self.pos):
                self.val = None
                self.cursor += 3
                return
            elif self.tok == '\n':
                if self.cursor == len(self.src):
                    self.tok = None
                    return
                self.line += 1
                self.line_pos = self.cursor
            elif not self.tok.isspace():
                raise QAPIParseError(self, 'Stray "%s"' % self.tok)

    def get_members(self):
        expr = OrderedDict()
        if self.tok == '}':
            self.accept()
            return expr
        if self.tok != "'":
            raise QAPIParseError(self, 'Expected string or "}"')
        while True:
            key = self.val
            self.accept()
            if self.tok != ':':
                raise QAPIParseError(self, 'Expected ":"')
            self.accept()
            if key in expr:
                raise QAPIParseError(self, 'Duplicate key "%s"' % key)
            expr[key] = self.get_expr(True)
            if self.tok == '}':
                self.accept()
                return expr
            if self.tok != ',':
                raise QAPIParseError(self, 'Expected "," or "}"')
            self.accept()
            if self.tok != "'":
                raise QAPIParseError(self, 'Expected string')

    def get_values(self):
        expr = []
        if self.tok == ']':
            self.accept()
            return expr
        if self.tok not in "{['tfn":
            raise QAPIParseError(self, 'Expected "{", "[", "]", string, '
                                 'boolean or "null"')
        while True:
            expr.append(self.get_expr(True))
            if self.tok == ']':
                self.accept()
                return expr
            if self.tok != ',':
                raise QAPIParseError(self, 'Expected "," or "]"')
            self.accept()

    def get_expr(self, nested):
        if self.tok != '{' and not nested:
            raise QAPIParseError(self, 'Expected "{"')
        if self.tok == '{':
            self.accept()
            expr = self.get_members()
        elif self.tok == '[':
            self.accept()
            expr = self.get_values()
        elif self.tok in "'tfn":
            expr = self.val
            self.accept()
        else:
            raise QAPIParseError(self, 'Expected "{", "[", string, '
                                 'boolean or "null"')
        return expr

    def get_doc(self, info):
        if self.val != '##':
            raise QAPIParseError(self, "Junk after '##' at start of "
                                 "documentation comment")

        doc = QAPIDoc(self, info)
        self.accept(False)
        while self.tok == '#':
            if self.val.startswith('##'):
                # End of doc comment
                if self.val != '##':
                    raise QAPIParseError(self, "Junk after '##' at end of "
                                         "documentation comment")
                doc.end_comment()
                self.accept()
                return doc
            else:
                doc.append(self.val)
            self.accept(False)

        raise QAPIParseError(self, "Documentation comment must end with '##'")


#
# Semantic analysis of schema expressions
# TODO fold into QAPISchema
# TODO catching name collisions in generated code would be nice
#


def find_base_members(base):
    if isinstance(base, dict):
        return base
    base_struct_define = struct_types.get(base)
    if not base_struct_define:
        return None
    return base_struct_define['data']


# Return the qtype of an alternate branch, or None on error.
def find_alternate_member_qtype(qapi_type):
    if qapi_type in builtin_types:
        return builtin_types[qapi_type]
    elif qapi_type in struct_types:
        return 'QTYPE_QDICT'
    elif qapi_type in enum_types:
        return 'QTYPE_QSTRING'
    elif qapi_type in union_types:
        return 'QTYPE_QDICT'
    return None


# Return the discriminator enum define if discriminator is specified as an
# enum type, otherwise return None.
def discriminator_find_enum_define(expr):
    base = expr.get('base')
    discriminator = expr.get('discriminator')

    if not (discriminator and base):
        return None

    base_members = find_base_members(base)
    if not base_members:
        return None

    discriminator_value = base_members.get(discriminator)
    if not discriminator_value:
        return None

    return enum_types.get(discriminator_value['type'])


# Names must be letters, numbers, -, and _.  They must start with letter,
# except for downstream extensions which must start with __RFQDN_.
# Dots are only valid in the downstream extension prefix.
valid_name = re.compile(r'^(__[a-zA-Z0-9.-]+_)?'
                        '[a-zA-Z][a-zA-Z0-9_-]*$')


def check_name(info, source, name, allow_optional=False,
               enum_member=False):
    global valid_name
    membername = name

    if not isinstance(name, str):
        raise QAPISemError(info, "%s requires a string name" % source)
    if name.startswith('*'):
        membername = name[1:]
        if not allow_optional:
            raise QAPISemError(info, "%s does not allow optional name '%s'"
                               % (source, name))
    # Enum members can start with a digit, because the generated C
    # code always prefixes it with the enum name
    if enum_member and membername[0].isdigit():
        membername = 'D' + membername
    # Reserve the entire 'q_' namespace for c_name(), and for 'q_empty'
    # and 'q_obj_*' implicit type names.
    if not valid_name.match(membername) or \
       c_name(membername, False).startswith('q_'):
        raise QAPISemError(info, "%s uses invalid name '%s'" % (source, name))


def add_name(name, info, meta, implicit=False):
    global all_names
    check_name(info, "'%s'" % meta, name)
    # FIXME should reject names that differ only in '_' vs. '.'
    # vs. '-', because they're liable to clash in generated C.
    if name in all_names:
        raise QAPISemError(info, "%s '%s' is already defined"
                           % (all_names[name], name))
    if not implicit and (name.endswith('Kind') or name.endswith('List')):
        raise QAPISemError(info, "%s '%s' should not end in '%s'"
                           % (meta, name, name[-4:]))
    all_names[name] = meta


def check_if(expr, info):

    def check_if_str(ifcond, info):
        if not isinstance(ifcond, str):
            raise QAPISemError(
                info, "'if' condition must be a string or a list of strings")
        if ifcond == '':
            raise QAPISemError(info, "'if' condition '' makes no sense")

    ifcond = expr.get('if')
    if ifcond is None:
        return
    if isinstance(ifcond, list):
        if ifcond == []:
            raise QAPISemError(info, "'if' condition [] is useless")
        for elt in ifcond:
            check_if_str(elt, info)
    else:
        check_if_str(ifcond, info)


def check_type(info, source, value,
               allow_array=False, allow_dict=False, allow_metas=[]):
    global all_names

    if value is None:
        return

    # Check if array type for value is okay
    if isinstance(value, list):
        if not allow_array:
            raise QAPISemError(info, "%s cannot be an array" % source)
        if len(value) != 1 or not isinstance(value[0], str):
            raise QAPISemError(info,
                               "%s: array type must contain single type name" %
                               source)
        value = value[0]

    # Check if type name for value is okay
    if isinstance(value, str):
        if value not in all_names:
            raise QAPISemError(info, "%s uses unknown type '%s'"
                               % (source, value))
        if not all_names[value] in allow_metas:
            raise QAPISemError(info, "%s cannot use %s type '%s'" %
                               (source, all_names[value], value))
        return

    if not allow_dict:
        raise QAPISemError(info, "%s should be a type name" % source)

    if not isinstance(value, OrderedDict):
        raise QAPISemError(info,
                           "%s should be a dictionary or type name" % source)

    # value is a dictionary, check that each member is okay
    for (key, arg) in value.items():
        check_name(info, "Member of %s" % source, key,
                   allow_optional=True)
        if c_name(key, False) == 'u' or c_name(key, False).startswith('has_'):
            raise QAPISemError(info, "Member of %s uses reserved name '%s'"
                               % (source, key))
        # Todo: allow dictionaries to represent default values of
        # an optional argument.
        check_known_keys(info, "member '%s' of %s" % (key, source),
                         arg, ['type'], ['if'])
        check_type(info, "Member '%s' of %s" % (key, source),
                   arg['type'], allow_array=True,
                   allow_metas=['built-in', 'union', 'alternate', 'struct',
                                'enum'])


def check_command(expr, info):
    name = expr['command']
    boxed = expr.get('boxed', False)

    args_meta = ['struct']
    if boxed:
        args_meta += ['union']
    check_type(info, "'data' for command '%s'" % name,
               expr.get('data'), allow_dict=not boxed,
               allow_metas=args_meta)
    returns_meta = ['union', 'struct']
    if name in returns_whitelist:
        returns_meta += ['built-in', 'alternate', 'enum']
    check_type(info, "'returns' for command '%s'" % name,
               expr.get('returns'), allow_array=True,
               allow_metas=returns_meta)


def check_event(expr, info):
    name = expr['event']
    boxed = expr.get('boxed', False)

    meta = ['struct']
    if boxed:
        meta += ['union']
    check_type(info, "'data' for event '%s'" % name,
               expr.get('data'), allow_dict=not boxed,
               allow_metas=meta)


def enum_get_names(expr):
    return [e['name'] for e in expr['data']]


def check_union(expr, info):
    name = expr['union']
    base = expr.get('base')
    discriminator = expr.get('discriminator')
    members = expr['data']

    # Two types of unions, determined by discriminator.

    # With no discriminator it is a simple union.
    if discriminator is None:
        enum_values = members.keys()
        allow_metas = ['built-in', 'union', 'alternate', 'struct', 'enum']
        if base is not None:
            raise QAPISemError(info, "Simple union '%s' must not have a base" %
                               name)

    # Else, it's a flat union.
    else:
        # The object must have a string or dictionary 'base'.
        check_type(info, "'base' for union '%s'" % name,
                   base, allow_dict=True,
                   allow_metas=['struct'])
        if not base:
            raise QAPISemError(info, "Flat union '%s' must have a base"
                               % name)
        base_members = find_base_members(base)
        assert base_members is not None

        # The value of member 'discriminator' must name a non-optional
        # member of the base struct.
        check_name(info, "Discriminator of flat union '%s'" % name,
                   discriminator)
        discriminator_value = base_members.get(discriminator)
        if not discriminator_value:
            raise QAPISemError(info,
                               "Discriminator '%s' is not a member of base "
                               "struct '%s'"
                               % (discriminator, base))
        if discriminator_value.get('if'):
            raise QAPISemError(info, 'The discriminator %s.%s for union %s '
                               'must not be conditional' %
                               (base, discriminator, name))
        enum_define = enum_types.get(discriminator_value['type'])
        # Do not allow string discriminator
        if not enum_define:
            raise QAPISemError(info,
                               "Discriminator '%s' must be of enumeration "
                               "type" % discriminator)
        enum_values = enum_get_names(enum_define)
        allow_metas = ['struct']

    if (len(enum_values) == 0):
        raise QAPISemError(info, "Union '%s' has no branches" % name)

    for (key, value) in members.items():
        check_name(info, "Member of union '%s'" % name, key)

        check_known_keys(info, "member '%s' of union '%s'" % (key, name),
                         value, ['type'], ['if'])
        # Each value must name a known type
        check_type(info, "Member '%s' of union '%s'" % (key, name),
                   value['type'],
                   allow_array=not base, allow_metas=allow_metas)

        # If the discriminator names an enum type, then all members
        # of 'data' must also be members of the enum type.
        if discriminator is not None:
            if key not in enum_values:
                raise QAPISemError(info,
                                   "Discriminator value '%s' is not found in "
                                   "enum '%s'"
                                   % (key, enum_define['enum']))


def check_alternate(expr, info):
    name = expr['alternate']
    members = expr['data']
    types_seen = {}

    if len(members) == 0:
        raise QAPISemError(info,
                           "Alternate '%s' cannot have empty 'data'" % name)
    for (key, value) in members.items():
        check_name(info, "Member of alternate '%s'" % name, key)
        check_known_keys(info,
                         "member '%s' of alternate '%s'" % (key, name),
                         value, ['type'], ['if'])
        typ = value['type']

        # Ensure alternates have no type conflicts.
        check_type(info, "Member '%s' of alternate '%s'" % (key, name), typ,
                   allow_metas=['built-in', 'union', 'struct', 'enum'])
        qtype = find_alternate_member_qtype(typ)
        if not qtype:
            raise QAPISemError(info, "Alternate '%s' member '%s' cannot use "
                               "type '%s'" % (name, key, typ))
        conflicting = set([qtype])
        if qtype == 'QTYPE_QSTRING':
            enum_expr = enum_types.get(typ)
            if enum_expr:
                for v in enum_get_names(enum_expr):
                    if v in ['on', 'off']:
                        conflicting.add('QTYPE_QBOOL')
                    if re.match(r'[-+0-9.]', v): # lazy, could be tightened
                        conflicting.add('QTYPE_QNUM')
            else:
                conflicting.add('QTYPE_QNUM')
                conflicting.add('QTYPE_QBOOL')
        for qt in conflicting:
            if qt in types_seen:
                raise QAPISemError(info, "Alternate '%s' member '%s' can't "
                                   "be distinguished from member '%s'"
                                   % (name, key, types_seen[qt]))
            types_seen[qt] = key


def check_enum(expr, info):
    name = expr['enum']
    members = expr['data']
    prefix = expr.get('prefix')

    if not isinstance(members, list):
        raise QAPISemError(info,
                           "Enum '%s' requires an array for 'data'" % name)
    if prefix is not None and not isinstance(prefix, str):
        raise QAPISemError(info,
                           "Enum '%s' requires a string for 'prefix'" % name)

    for member in members:
        source = "dictionary member of enum '%s'" % name
        check_known_keys(info, source, member, ['name'], ['if'])
        check_if(member, info)
        check_name(info, "Member of enum '%s'" % name, member['name'],
                   enum_member=True)


def check_struct(expr, info):
    name = expr['struct']
    members = expr['data']
    features = expr.get('features')

    check_type(info, "'data' for struct '%s'" % name, members,
               allow_dict=True)
    check_type(info, "'base' for struct '%s'" % name, expr.get('base'),
               allow_metas=['struct'])

    if features:
        if not isinstance(features, list):
            raise QAPISemError(info,
                               "Struct '%s' requires an array for 'features'" %
                               name)
        for f in features:
            assert isinstance(f, dict)
            check_known_keys(info, "feature of struct %s" % name, f,
                             ['name'], ['if'])

            check_if(f, info)
            check_name(info, "Feature of struct %s" % name, f['name'])


def check_known_keys(info, source, keys, required, optional):

    def pprint(elems):
        return ', '.join("'" + e + "'" for e in sorted(elems))

    missing = set(required) - set(keys)
    if missing:
        raise QAPISemError(info, "Key%s %s %s missing from %s"
                           % ('s' if len(missing) > 1 else '', pprint(missing),
                              'are' if len(missing) > 1 else 'is', source))
    allowed = set(required + optional)
    unknown = set(keys) - allowed
    if unknown:
        raise QAPISemError(info, "Unknown key%s %s in %s\nValid keys are %s."
                           % ('s' if len(unknown) > 1 else '', pprint(unknown),
                              source, pprint(allowed)))


def check_keys(expr_elem, meta, required, optional=[]):
    expr = expr_elem['expr']
    info = expr_elem['info']
    name = expr[meta]
    if not isinstance(name, str):
        raise QAPISemError(info, "'%s' key must have a string value" % meta)
    required = required + [meta]
    source = "%s '%s'" % (meta, name)
    check_known_keys(info, source, expr.keys(), required, optional)
    for (key, value) in expr.items():
        if key in ['gen', 'success-response'] and value is not False:
            raise QAPISemError(info,
                               "'%s' of %s '%s' should only use false value"
                               % (key, meta, name))
        if (key in ['boxed', 'allow-oob', 'allow-preconfig']
                and value is not True):
            raise QAPISemError(info,
                               "'%s' of %s '%s' should only use true value"
                               % (key, meta, name))
        if key == 'if':
            check_if(expr, info)


def normalize_enum(expr):
    if isinstance(expr['data'], list):
        expr['data'] = [m if isinstance(m, dict) else {'name': m}
                        for m in expr['data']]


def normalize_members(members):
    if isinstance(members, OrderedDict):
        for key, arg in members.items():
            if isinstance(arg, dict):
                continue
            members[key] = {'type': arg}


def normalize_features(features):
    if isinstance(features, list):
        features[:] = [f if isinstance(f, dict) else {'name': f}
                       for f in features]


def check_exprs(exprs):
    global all_names

    # Populate name table with names of built-in types
    for builtin in builtin_types.keys():
        all_names[builtin] = 'built-in'

    # Learn the types and check for valid expression keys
    for expr_elem in exprs:
        expr = expr_elem['expr']
        info = expr_elem['info']
        doc = expr_elem.get('doc')

        if 'include' in expr:
            continue

        if not doc and doc_required:
            raise QAPISemError(info,
                               "Expression missing documentation comment")

        if 'enum' in expr:
            meta = 'enum'
            check_keys(expr_elem, 'enum', ['data'], ['if', 'prefix'])
            normalize_enum(expr)
            enum_types[expr[meta]] = expr
        elif 'union' in expr:
            meta = 'union'
            check_keys(expr_elem, 'union', ['data'],
                       ['base', 'discriminator', 'if'])
            normalize_members(expr.get('base'))
            normalize_members(expr['data'])
            union_types[expr[meta]] = expr
        elif 'alternate' in expr:
            meta = 'alternate'
            check_keys(expr_elem, 'alternate', ['data'], ['if'])
            normalize_members(expr['data'])
        elif 'struct' in expr:
            meta = 'struct'
            check_keys(expr_elem, 'struct', ['data'],
                       ['base', 'if', 'features'])
            normalize_members(expr['data'])
            normalize_features(expr.get('features'))
            struct_types[expr[meta]] = expr
        elif 'command' in expr:
            meta = 'command'
            check_keys(expr_elem, 'command', [],
                       ['data', 'returns', 'gen', 'success-response',
                        'boxed', 'allow-oob', 'allow-preconfig', 'if'])
            normalize_members(expr.get('data'))
        elif 'event' in expr:
            meta = 'event'
            check_keys(expr_elem, 'event', [], ['data', 'boxed', 'if'])
            normalize_members(expr.get('data'))
        else:
            raise QAPISemError(expr_elem['info'],
                               "Expression is missing metatype")
        name = expr[meta]
        add_name(name, info, meta)
        if doc and doc.symbol != name:
            raise QAPISemError(info, "Definition of '%s' follows documentation"
                               " for '%s'" % (name, doc.symbol))

    # Try again for hidden UnionKind enum
    for expr_elem in exprs:
        expr = expr_elem['expr']

        if 'include' in expr:
            continue
        if 'union' in expr and not discriminator_find_enum_define(expr):
            name = '%sKind' % expr['union']
        elif 'alternate' in expr:
            name = '%sKind' % expr['alternate']
        else:
            continue
        enum_types[name] = {'enum': name}
        add_name(name, info, 'enum', implicit=True)

    # Validate that exprs make sense
    for expr_elem in exprs:
        expr = expr_elem['expr']
        info = expr_elem['info']
        doc = expr_elem.get('doc')

        if 'include' in expr:
            continue
        if 'enum' in expr:
            check_enum(expr, info)
        elif 'union' in expr:
            check_union(expr, info)
        elif 'alternate' in expr:
            check_alternate(expr, info)
        elif 'struct' in expr:
            check_struct(expr, info)
        elif 'command' in expr:
            check_command(expr, info)
        elif 'event' in expr:
            check_event(expr, info)
        else:
            assert False, 'unexpected meta type'

        if doc:
            doc.check_expr(expr)

    return exprs


#
# Schema compiler frontend
#

def listify_cond(ifcond):
    if not ifcond:
        return []
    if not isinstance(ifcond, list):
        return [ifcond]
    return ifcond


class QAPISchemaEntity(object):
    def __init__(self, name, info, doc, ifcond=None):
        assert name is None or isinstance(name, str)
        self.name = name
        self.module = None
        # For explicitly defined entities, info points to the (explicit)
        # definition.  For builtins (and their arrays), info is None.
        # For implicitly defined entities, info points to a place that
        # triggered the implicit definition (there may be more than one
        # such place).
        self.info = info
        self.doc = doc
        self._ifcond = ifcond  # self.ifcond is set only after .check()

    def c_name(self):
        return c_name(self.name)

    def check(self, schema):
        if isinstance(self._ifcond, QAPISchemaType):
            # inherit the condition from a type
            typ = self._ifcond
            typ.check(schema)
            self.ifcond = typ.ifcond
        else:
            self.ifcond = listify_cond(self._ifcond)
        if self.info:
            self.module = os.path.relpath(self.info['file'],
                                          os.path.dirname(schema.fname))

    def is_implicit(self):
        return not self.info

    def visit(self, visitor):
        pass


class QAPISchemaVisitor(object):
    def visit_begin(self, schema):
        pass

    def visit_end(self):
        pass

    def visit_module(self, fname):
        pass

    def visit_needed(self, entity):
        # Default to visiting everything
        return True

    def visit_include(self, fname, info):
        pass

    def visit_builtin_type(self, name, info, json_type):
        pass

    def visit_enum_type(self, name, info, ifcond, members, prefix):
        pass

    def visit_array_type(self, name, info, ifcond, element_type):
        pass

    def visit_object_type(self, name, info, ifcond, base, members, variants,
                          features):
        pass

    def visit_object_type_flat(self, name, info, ifcond, members, variants,
                               features):
        pass

    def visit_alternate_type(self, name, info, ifcond, variants):
        pass

    def visit_command(self, name, info, ifcond, arg_type, ret_type, gen,
                      success_response, boxed, allow_oob, allow_preconfig):
        pass

    def visit_event(self, name, info, ifcond, arg_type, boxed):
        pass


class QAPISchemaInclude(QAPISchemaEntity):

    def __init__(self, fname, info):
        QAPISchemaEntity.__init__(self, None, info, None)
        self.fname = fname

    def visit(self, visitor):
        visitor.visit_include(self.fname, self.info)


class QAPISchemaType(QAPISchemaEntity):
    # Return the C type for common use.
    # For the types we commonly box, this is a pointer type.
    def c_type(self):
        pass

    # Return the C type to be used in a parameter list.
    def c_param_type(self):
        return self.c_type()

    # Return the C type to be used where we suppress boxing.
    def c_unboxed_type(self):
        return self.c_type()

    def json_type(self):
        pass

    def alternate_qtype(self):
        json2qtype = {
            'null':    'QTYPE_QNULL',
            'string':  'QTYPE_QSTRING',
            'number':  'QTYPE_QNUM',
            'int':     'QTYPE_QNUM',
            'boolean': 'QTYPE_QBOOL',
            'object':  'QTYPE_QDICT'
        }
        return json2qtype.get(self.json_type())

    def doc_type(self):
        if self.is_implicit():
            return None
        return self.name


class QAPISchemaBuiltinType(QAPISchemaType):
    def __init__(self, name, json_type, c_type):
        QAPISchemaType.__init__(self, name, None, None)
        assert not c_type or isinstance(c_type, str)
        assert json_type in ('string', 'number', 'int', 'boolean', 'null',
                             'value')
        self._json_type_name = json_type
        self._c_type_name = c_type

    def c_name(self):
        return self.name

    def c_type(self):
        return self._c_type_name

    def c_param_type(self):
        if self.name == 'str':
            return 'const ' + self._c_type_name
        return self._c_type_name

    def json_type(self):
        return self._json_type_name

    def doc_type(self):
        return self.json_type()

    def visit(self, visitor):
        visitor.visit_builtin_type(self.name, self.info, self.json_type())


class QAPISchemaEnumType(QAPISchemaType):
    def __init__(self, name, info, doc, ifcond, members, prefix):
        QAPISchemaType.__init__(self, name, info, doc, ifcond)
        for m in members:
            assert isinstance(m, QAPISchemaMember)
            m.set_owner(name)
        assert prefix is None or isinstance(prefix, str)
        self.members = members
        self.prefix = prefix

    def check(self, schema):
        QAPISchemaType.check(self, schema)
        seen = {}
        for m in self.members:
            m.check_clash(self.info, seen)
            if self.doc:
                self.doc.connect_member(m)

    def is_implicit(self):
        # See QAPISchema._make_implicit_enum_type() and ._def_predefineds()
        return self.name.endswith('Kind') or self.name == 'QType'

    def c_type(self):
        return c_name(self.name)

    def member_names(self):
        return [m.name for m in self.members]

    def json_type(self):
        return 'string'

    def visit(self, visitor):
        visitor.visit_enum_type(self.name, self.info, self.ifcond,
                                self.members, self.prefix)


class QAPISchemaArrayType(QAPISchemaType):
    def __init__(self, name, info, element_type):
        QAPISchemaType.__init__(self, name, info, None, None)
        assert isinstance(element_type, str)
        self._element_type_name = element_type
        self.element_type = None

    def check(self, schema):
        QAPISchemaType.check(self, schema)
        self.element_type = schema.lookup_type(self._element_type_name)
        assert self.element_type
        self.element_type.check(schema)
        self.module = self.element_type.module
        self.ifcond = self.element_type.ifcond

    def is_implicit(self):
        return True

    def c_type(self):
        return c_name(self.name) + pointer_suffix

    def json_type(self):
        return 'array'

    def doc_type(self):
        elt_doc_type = self.element_type.doc_type()
        if not elt_doc_type:
            return None
        return 'array of ' + elt_doc_type

    def visit(self, visitor):
        visitor.visit_array_type(self.name, self.info, self.ifcond,
                                 self.element_type)


class QAPISchemaObjectType(QAPISchemaType):
    def __init__(self, name, info, doc, ifcond,
                 base, local_members, variants, features):
        # struct has local_members, optional base, and no variants
        # flat union has base, variants, and no local_members
        # simple union has local_members, variants, and no base
        QAPISchemaType.__init__(self, name, info, doc, ifcond)
        assert base is None or isinstance(base, str)
        for m in local_members:
            assert isinstance(m, QAPISchemaObjectTypeMember)
            m.set_owner(name)
        if variants is not None:
            assert isinstance(variants, QAPISchemaObjectTypeVariants)
            variants.set_owner(name)
        for f in features:
            assert isinstance(f, QAPISchemaFeature)
            f.set_owner(name)
        self._base_name = base
        self.base = None
        self.local_members = local_members
        self.variants = variants
        self.members = None
        self.features = features

    def check(self, schema):
        QAPISchemaType.check(self, schema)
        if self.members is False:               # check for cycles
            raise QAPISemError(self.info,
                               "Object %s contains itself" % self.name)
        if self.members:
            return
        self.members = False                    # mark as being checked
        seen = OrderedDict()
        if self._base_name:
            self.base = schema.lookup_type(self._base_name)
            assert isinstance(self.base, QAPISchemaObjectType)
            self.base.check(schema)
            self.base.check_clash(self.info, seen)
        for m in self.local_members:
            m.check(schema)
            m.check_clash(self.info, seen)
            if self.doc:
                self.doc.connect_member(m)
        self.members = seen.values()
        if self.variants:
            self.variants.check(schema, seen)
            assert self.variants.tag_member in self.members
            self.variants.check_clash(self.info, seen)

        # Features are in a name space separate from members
        seen = {}
        for f in self.features:
            f.check_clash(self.info, seen)

        if self.doc:
            self.doc.check()

    # Check that the members of this type do not cause duplicate JSON members,
    # and update seen to track the members seen so far. Report any errors
    # on behalf of info, which is not necessarily self.info
    def check_clash(self, info, seen):
        assert not self.variants       # not implemented
        for m in self.members:
            m.check_clash(info, seen)

    def is_implicit(self):
        # See QAPISchema._make_implicit_object_type(), as well as
        # _def_predefineds()
        return self.name.startswith('q_')

    def is_empty(self):
        assert self.members is not None
        return not self.members and not self.variants

    def c_name(self):
        assert self.name != 'q_empty'
        return QAPISchemaType.c_name(self)

    def c_type(self):
        assert not self.is_implicit()
        return c_name(self.name) + pointer_suffix

    def c_unboxed_type(self):
        return c_name(self.name)

    def json_type(self):
        return 'object'

    def visit(self, visitor):
        visitor.visit_object_type(self.name, self.info, self.ifcond,
                                  self.base, self.local_members, self.variants,
                                  self.features)
        visitor.visit_object_type_flat(self.name, self.info, self.ifcond,
                                       self.members, self.variants,
                                       self.features)


class QAPISchemaMember(object):
    """ Represents object members, enum members and features """
    role = 'member'

    def __init__(self, name, ifcond=None):
        assert isinstance(name, str)
        self.name = name
        self.ifcond = listify_cond(ifcond)
        self.owner = None

    def set_owner(self, name):
        assert not self.owner
        self.owner = name

    def check_clash(self, info, seen):
        cname = c_name(self.name)
        if cname.lower() != cname and self.owner not in name_case_whitelist:
            raise QAPISemError(info,
                               "%s should not use uppercase" % self.describe())
        if cname in seen:
            raise QAPISemError(info, "%s collides with %s" %
                               (self.describe(), seen[cname].describe()))
        seen[cname] = self

    def _pretty_owner(self):
        owner = self.owner
        if owner.startswith('q_obj_'):
            # See QAPISchema._make_implicit_object_type() - reverse the
            # mapping there to create a nice human-readable description
            owner = owner[6:]
            if owner.endswith('-arg'):
                return '(parameter of %s)' % owner[:-4]
            elif owner.endswith('-base'):
                return '(base of %s)' % owner[:-5]
            else:
                assert owner.endswith('-wrapper')
                # Unreachable and not implemented
                assert False
        if owner.endswith('Kind'):
            # See QAPISchema._make_implicit_enum_type()
            return '(branch of %s)' % owner[:-4]
        return '(%s of %s)' % (self.role, owner)

    def describe(self):
        return "'%s' %s" % (self.name, self._pretty_owner())


class QAPISchemaFeature(QAPISchemaMember):
    role = 'feature'


class QAPISchemaObjectTypeMember(QAPISchemaMember):
    def __init__(self, name, typ, optional, ifcond=None):
        QAPISchemaMember.__init__(self, name, ifcond)
        assert isinstance(typ, str)
        assert isinstance(optional, bool)
        self._type_name = typ
        self.type = None
        self.optional = optional

    def check(self, schema):
        assert self.owner
        self.type = schema.lookup_type(self._type_name)
        assert self.type


class QAPISchemaObjectTypeVariants(object):
    def __init__(self, tag_name, tag_member, variants):
        # Flat unions pass tag_name but not tag_member.
        # Simple unions and alternates pass tag_member but not tag_name.
        # After check(), tag_member is always set, and tag_name remains
        # a reliable witness of being used by a flat union.
        assert bool(tag_member) != bool(tag_name)
        assert (isinstance(tag_name, str) or
                isinstance(tag_member, QAPISchemaObjectTypeMember))
        for v in variants:
            assert isinstance(v, QAPISchemaObjectTypeVariant)
        self._tag_name = tag_name
        self.tag_member = tag_member
        self.variants = variants

    def set_owner(self, name):
        for v in self.variants:
            v.set_owner(name)

    def check(self, schema, seen):
        if not self.tag_member:    # flat union
            self.tag_member = seen[c_name(self._tag_name)]
            assert self._tag_name == self.tag_member.name
        assert isinstance(self.tag_member.type, QAPISchemaEnumType)
        if self._tag_name:    # flat union
            # branches that are not explicitly covered get an empty type
            cases = set([v.name for v in self.variants])
            for m in self.tag_member.type.members:
                if m.name not in cases:
                    v = QAPISchemaObjectTypeVariant(m.name, 'q_empty',
                                                    m.ifcond)
                    v.set_owner(self.tag_member.owner)
                    self.variants.append(v)
        for v in self.variants:
            v.check(schema)
            # Union names must match enum values; alternate names are
            # checked separately. Use 'seen' to tell the two apart.
            if seen:
                assert v.name in self.tag_member.type.member_names()
                assert isinstance(v.type, QAPISchemaObjectType)
                v.type.check(schema)

    def check_clash(self, info, seen):
        for v in self.variants:
            # Reset seen map for each variant, since qapi names from one
            # branch do not affect another branch
            assert isinstance(v.type, QAPISchemaObjectType)
            v.type.check_clash(info, dict(seen))


class QAPISchemaObjectTypeVariant(QAPISchemaObjectTypeMember):
    role = 'branch'

    def __init__(self, name, typ, ifcond=None):
        QAPISchemaObjectTypeMember.__init__(self, name, typ, False, ifcond)


class QAPISchemaAlternateType(QAPISchemaType):
    def __init__(self, name, info, doc, ifcond, variants):
        QAPISchemaType.__init__(self, name, info, doc, ifcond)
        assert isinstance(variants, QAPISchemaObjectTypeVariants)
        assert variants.tag_member
        variants.set_owner(name)
        variants.tag_member.set_owner(self.name)
        self.variants = variants

    def check(self, schema):
        QAPISchemaType.check(self, schema)
        self.variants.tag_member.check(schema)
        # Not calling self.variants.check_clash(), because there's nothing
        # to clash with
        self.variants.check(schema, {})
        # Alternate branch names have no relation to the tag enum values;
        # so we have to check for potential name collisions ourselves.
        seen = {}
        for v in self.variants.variants:
            v.check_clash(self.info, seen)
            if self.doc:
                self.doc.connect_member(v)
        if self.doc:
            self.doc.check()

    def c_type(self):
        return c_name(self.name) + pointer_suffix

    def json_type(self):
        return 'value'

    def visit(self, visitor):
        visitor.visit_alternate_type(self.name, self.info, self.ifcond,
                                     self.variants)


class QAPISchemaCommand(QAPISchemaEntity):
    def __init__(self, name, info, doc, ifcond, arg_type, ret_type,
                 gen, success_response, boxed, allow_oob, allow_preconfig):
        QAPISchemaEntity.__init__(self, name, info, doc, ifcond)
        assert not arg_type or isinstance(arg_type, str)
        assert not ret_type or isinstance(ret_type, str)
        self._arg_type_name = arg_type
        self.arg_type = None
        self._ret_type_name = ret_type
        self.ret_type = None
        self.gen = gen
        self.success_response = success_response
        self.boxed = boxed
        self.allow_oob = allow_oob
        self.allow_preconfig = allow_preconfig

    def check(self, schema):
        QAPISchemaEntity.check(self, schema)
        if self._arg_type_name:
            self.arg_type = schema.lookup_type(self._arg_type_name)
            assert isinstance(self.arg_type, QAPISchemaObjectType)
            self.arg_type.check(schema)
            assert not self.arg_type.variants or self.boxed
        elif self.boxed:
            raise QAPISemError(self.info, "Use of 'boxed' requires 'data'")
        if self._ret_type_name:
            self.ret_type = schema.lookup_type(self._ret_type_name)
            assert isinstance(self.ret_type, QAPISchemaType)

    def visit(self, visitor):
        visitor.visit_command(self.name, self.info, self.ifcond,
                              self.arg_type, self.ret_type,
                              self.gen, self.success_response,
                              self.boxed, self.allow_oob,
                              self.allow_preconfig)


class QAPISchemaEvent(QAPISchemaEntity):
    def __init__(self, name, info, doc, ifcond, arg_type, boxed):
        QAPISchemaEntity.__init__(self, name, info, doc, ifcond)
        assert not arg_type or isinstance(arg_type, str)
        self._arg_type_name = arg_type
        self.arg_type = None
        self.boxed = boxed

    def check(self, schema):
        QAPISchemaEntity.check(self, schema)
        if self._arg_type_name:
            self.arg_type = schema.lookup_type(self._arg_type_name)
            assert isinstance(self.arg_type, QAPISchemaObjectType)
            self.arg_type.check(schema)
            assert not self.arg_type.variants or self.boxed
        elif self.boxed:
            raise QAPISemError(self.info, "Use of 'boxed' requires 'data'")

    def visit(self, visitor):
        visitor.visit_event(self.name, self.info, self.ifcond,
                            self.arg_type, self.boxed)


class QAPISchema(object):
    def __init__(self, fname):
        self.fname = fname
        if sys.version_info[0] >= 3:
            f = open(fname, 'r', encoding='utf-8')
        else:
            f = open(fname, 'r')
        parser = QAPISchemaParser(f)
        exprs = check_exprs(parser.exprs)
        self.docs = parser.docs
        self._entity_list = []
        self._entity_dict = {}
        self._predefining = True
        self._def_predefineds()
        self._predefining = False
        self._def_exprs(exprs)
        self.check()

    def _def_entity(self, ent):
        # Only the predefined types are allowed to not have info
        assert ent.info or self._predefining
        assert ent.name is None or ent.name not in self._entity_dict
        self._entity_list.append(ent)
        if ent.name is not None:
            self._entity_dict[ent.name] = ent

    def lookup_entity(self, name, typ=None):
        ent = self._entity_dict.get(name)
        if typ and not isinstance(ent, typ):
            return None
        return ent

    def lookup_type(self, name):
        return self.lookup_entity(name, QAPISchemaType)

    def _def_include(self, expr, info, doc):
        include = expr['include']
        assert doc is None
        main_info = info
        while main_info['parent']:
            main_info = main_info['parent']
        fname = os.path.relpath(include, os.path.dirname(main_info['file']))
        self._def_entity(QAPISchemaInclude(fname, info))

    def _def_builtin_type(self, name, json_type, c_type):
        self._def_entity(QAPISchemaBuiltinType(name, json_type, c_type))
        # Instantiating only the arrays that are actually used would
        # be nice, but we can't as long as their generated code
        # (qapi-builtin-types.[ch]) may be shared by some other
        # schema.
        self._make_array_type(name, None)

    def _def_predefineds(self):
        for t in [('str',    'string',  'char' + pointer_suffix),
                  ('number', 'number',  'double'),
                  ('int',    'int',     'int64_t'),
                  ('int8',   'int',     'int8_t'),
                  ('int16',  'int',     'int16_t'),
                  ('int32',  'int',     'int32_t'),
                  ('int64',  'int',     'int64_t'),
                  ('uint8',  'int',     'uint8_t'),
                  ('uint16', 'int',     'uint16_t'),
                  ('uint32', 'int',     'uint32_t'),
                  ('uint64', 'int',     'uint64_t'),
                  ('size',   'int',     'uint64_t'),
                  ('bool',   'boolean', 'bool'),
                  ('any',    'value',   'QObject' + pointer_suffix),
                  ('null',   'null',    'QNull' + pointer_suffix)]:
            self._def_builtin_type(*t)
        self.the_empty_object_type = QAPISchemaObjectType(
            'q_empty', None, None, None, None, [], None, [])
        self._def_entity(self.the_empty_object_type)

        qtypes = ['none', 'qnull', 'qnum', 'qstring', 'qdict', 'qlist',
                  'qbool']
        qtype_values = self._make_enum_members([{'name': n} for n in qtypes])

        self._def_entity(QAPISchemaEnumType('QType', None, None, None,
                                            qtype_values, 'QTYPE'))

    def _make_features(self, features):
        return [QAPISchemaFeature(f['name'], f.get('if')) for f in features]

    def _make_enum_members(self, values):
        return [QAPISchemaMember(v['name'], v.get('if')) for v in values]

    def _make_implicit_enum_type(self, name, info, ifcond, values):
        # See also QAPISchemaObjectTypeMember._pretty_owner()
        name = name + 'Kind'   # Use namespace reserved by add_name()
        self._def_entity(QAPISchemaEnumType(
            name, info, None, ifcond, self._make_enum_members(values), None))
        return name

    def _make_array_type(self, element_type, info):
        name = element_type + 'List'   # Use namespace reserved by add_name()
        if not self.lookup_type(name):
            self._def_entity(QAPISchemaArrayType(name, info, element_type))
        return name

    def _make_implicit_object_type(self, name, info, doc, ifcond,
                                   role, members):
        if not members:
            return None
        # See also QAPISchemaObjectTypeMember._pretty_owner()
        name = 'q_obj_%s-%s' % (name, role)
        typ = self.lookup_entity(name, QAPISchemaObjectType)
        if typ:
            # The implicit object type has multiple users.  This can
            # happen only for simple unions' implicit wrapper types.
            # Its ifcond should be the disjunction of its user's
            # ifconds.  Not implemented.  Instead, we always pass the
            # wrapped type's ifcond, which is trivially the same for all
            # users.  It's also necessary for the wrapper to compile.
            # But it's not tight: the disjunction need not imply it.  We
            # may end up compiling useless wrapper types.
            # TODO kill simple unions or implement the disjunction
            assert ifcond == typ._ifcond # pylint: disable=protected-access
        else:
            self._def_entity(QAPISchemaObjectType(name, info, doc, ifcond,
                                                  None, members, None, []))
        return name

    def _def_enum_type(self, expr, info, doc):
        name = expr['enum']
        data = expr['data']
        prefix = expr.get('prefix')
        ifcond = expr.get('if')
        self._def_entity(QAPISchemaEnumType(
            name, info, doc, ifcond,
            self._make_enum_members(data), prefix))

    def _make_member(self, name, typ, ifcond, info):
        optional = False
        if name.startswith('*'):
            name = name[1:]
            optional = True
        if isinstance(typ, list):
            assert len(typ) == 1
            typ = self._make_array_type(typ[0], info)
        return QAPISchemaObjectTypeMember(name, typ, optional, ifcond)

    def _make_members(self, data, info):
        return [self._make_member(key, value['type'], value.get('if'), info)
                for (key, value) in data.items()]

    def _def_struct_type(self, expr, info, doc):
        name = expr['struct']
        base = expr.get('base')
        data = expr['data']
        ifcond = expr.get('if')
        features = expr.get('features', [])
        self._def_entity(QAPISchemaObjectType(name, info, doc, ifcond, base,
                                              self._make_members(data, info),
                                              None,
                                              self._make_features(features)))

    def _make_variant(self, case, typ, ifcond):
        return QAPISchemaObjectTypeVariant(case, typ, ifcond)

    def _make_simple_variant(self, case, typ, ifcond, info):
        if isinstance(typ, list):
            assert len(typ) == 1
            typ = self._make_array_type(typ[0], info)
        typ = self._make_implicit_object_type(
            typ, info, None, self.lookup_type(typ),
            'wrapper', [self._make_member('data', typ, None, info)])
        return QAPISchemaObjectTypeVariant(case, typ, ifcond)

    def _def_union_type(self, expr, info, doc):
        name = expr['union']
        data = expr['data']
        base = expr.get('base')
        ifcond = expr.get('if')
        tag_name = expr.get('discriminator')
        tag_member = None
        if isinstance(base, dict):
            base = self._make_implicit_object_type(
                name, info, doc, ifcond,
                'base', self._make_members(base, info))
        if tag_name:
            variants = [self._make_variant(key, value['type'], value.get('if'))
                        for (key, value) in data.items()]
            members = []
        else:
            variants = [self._make_simple_variant(key, value['type'],
                                                  value.get('if'), info)
                        for (key, value) in data.items()]
            enum = [{'name': v.name, 'if': v.ifcond} for v in variants]
            typ = self._make_implicit_enum_type(name, info, ifcond, enum)
            tag_member = QAPISchemaObjectTypeMember('type', typ, False)
            members = [tag_member]
        self._def_entity(
            QAPISchemaObjectType(name, info, doc, ifcond, base, members,
                                 QAPISchemaObjectTypeVariants(tag_name,
                                                              tag_member,
                                                              variants), []))

    def _def_alternate_type(self, expr, info, doc):
        name = expr['alternate']
        data = expr['data']
        ifcond = expr.get('if')
        variants = [self._make_variant(key, value['type'], value.get('if'))
                    for (key, value) in data.items()]
        tag_member = QAPISchemaObjectTypeMember('type', 'QType', False)
        self._def_entity(
            QAPISchemaAlternateType(name, info, doc, ifcond,
                                    QAPISchemaObjectTypeVariants(None,
                                                                 tag_member,
                                                                 variants)))

    def _def_command(self, expr, info, doc):
        name = expr['command']
        data = expr.get('data')
        rets = expr.get('returns')
        gen = expr.get('gen', True)
        success_response = expr.get('success-response', True)
        boxed = expr.get('boxed', False)
        allow_oob = expr.get('allow-oob', False)
        allow_preconfig = expr.get('allow-preconfig', False)
        ifcond = expr.get('if')
        if isinstance(data, OrderedDict):
            data = self._make_implicit_object_type(
                name, info, doc, ifcond, 'arg', self._make_members(data, info))
        if isinstance(rets, list):
            assert len(rets) == 1
            rets = self._make_array_type(rets[0], info)
        self._def_entity(QAPISchemaCommand(name, info, doc, ifcond, data, rets,
                                           gen, success_response,
                                           boxed, allow_oob, allow_preconfig))

    def _def_event(self, expr, info, doc):
        name = expr['event']
        data = expr.get('data')
        boxed = expr.get('boxed', False)
        ifcond = expr.get('if')
        if isinstance(data, OrderedDict):
            data = self._make_implicit_object_type(
                name, info, doc, ifcond, 'arg', self._make_members(data, info))
        self._def_entity(QAPISchemaEvent(name, info, doc, ifcond, data, boxed))

    def _def_exprs(self, exprs):
        for expr_elem in exprs:
            expr = expr_elem['expr']
            info = expr_elem['info']
            doc = expr_elem.get('doc')
            if 'enum' in expr:
                self._def_enum_type(expr, info, doc)
            elif 'struct' in expr:
                self._def_struct_type(expr, info, doc)
            elif 'union' in expr:
                self._def_union_type(expr, info, doc)
            elif 'alternate' in expr:
                self._def_alternate_type(expr, info, doc)
            elif 'command' in expr:
                self._def_command(expr, info, doc)
            elif 'event' in expr:
                self._def_event(expr, info, doc)
            elif 'include' in expr:
                self._def_include(expr, info, doc)
            else:
                assert False

    def check(self):
        for ent in self._entity_list:
            ent.check(self)

    def visit(self, visitor):
        visitor.visit_begin(self)
        module = None
        visitor.visit_module(module)
        for entity in self._entity_list:
            if visitor.visit_needed(entity):
                if entity.module != module:
                    module = entity.module
                    visitor.visit_module(module)
                entity.visit(visitor)
        visitor.visit_end()


#
# Code generation helpers
#

def camel_case(name):
    new_name = ''
    first = True
    for ch in name:
        if ch in ['_', '-']:
            first = True
        elif first:
            new_name += ch.upper()
            first = False
        else:
            new_name += ch.lower()
    return new_name


# ENUMName -> ENUM_NAME, EnumName1 -> ENUM_NAME1
# ENUM_NAME -> ENUM_NAME, ENUM_NAME1 -> ENUM_NAME1, ENUM_Name2 -> ENUM_NAME2
# ENUM24_Name -> ENUM24_NAME
def camel_to_upper(value):
    c_fun_str = c_name(value, False)
    if value.isupper():
        return c_fun_str

    new_name = ''
    length = len(c_fun_str)
    for i in range(length):
        c = c_fun_str[i]
        # When c is upper and no '_' appears before, do more checks
        if c.isupper() and (i > 0) and c_fun_str[i - 1] != '_':
            if i < length - 1 and c_fun_str[i + 1].islower():
                new_name += '_'
            elif c_fun_str[i - 1].isdigit():
                new_name += '_'
        new_name += c
    return new_name.lstrip('_').upper()


def c_enum_const(type_name, const_name, prefix=None):
    if prefix is not None:
        type_name = prefix
    return camel_to_upper(type_name) + '_' + c_name(const_name, False).upper()


if hasattr(str, 'maketrans'):
    c_name_trans = str.maketrans('.-', '__')
else:
    c_name_trans = string.maketrans('.-', '__')


# Map @name to a valid C identifier.
# If @protect, avoid returning certain ticklish identifiers (like
# C keywords) by prepending 'q_'.
#
# Used for converting 'name' from a 'name':'type' qapi definition
# into a generated struct member, as well as converting type names
# into substrings of a generated C function name.
# '__a.b_c' -> '__a_b_c', 'x-foo' -> 'x_foo'
# protect=True: 'int' -> 'q_int'; protect=False: 'int' -> 'int'
def c_name(name, protect=True):
    # ANSI X3J11/88-090, 3.1.1
    c89_words = set(['auto', 'break', 'case', 'char', 'const', 'continue',
                     'default', 'do', 'double', 'else', 'enum', 'extern',
                     'float', 'for', 'goto', 'if', 'int', 'long', 'register',
                     'return', 'short', 'signed', 'sizeof', 'static',
                     'struct', 'switch', 'typedef', 'union', 'unsigned',
                     'void', 'volatile', 'while'])
    # ISO/IEC 9899:1999, 6.4.1
    c99_words = set(['inline', 'restrict', '_Bool', '_Complex', '_Imaginary'])
    # ISO/IEC 9899:2011, 6.4.1
    c11_words = set(['_Alignas', '_Alignof', '_Atomic', '_Generic',
                     '_Noreturn', '_Static_assert', '_Thread_local'])
    # GCC http://gcc.gnu.org/onlinedocs/gcc-4.7.1/gcc/C-Extensions.html
    # excluding _.*
    gcc_words = set(['asm', 'typeof'])
    # C++ ISO/IEC 14882:2003 2.11
    cpp_words = set(['bool', 'catch', 'class', 'const_cast', 'delete',
                     'dynamic_cast', 'explicit', 'false', 'friend', 'mutable',
                     'namespace', 'new', 'operator', 'private', 'protected',
                     'public', 'reinterpret_cast', 'static_cast', 'template',
                     'this', 'throw', 'true', 'try', 'typeid', 'typename',
                     'using', 'virtual', 'wchar_t',
                     # alternative representations
                     'and', 'and_eq', 'bitand', 'bitor', 'compl', 'not',
                     'not_eq', 'or', 'or_eq', 'xor', 'xor_eq'])
    # namespace pollution:
    polluted_words = set(['unix', 'errno', 'mips', 'sparc', 'i386'])
    name = name.translate(c_name_trans)
    if protect and (name in c89_words | c99_words | c11_words | gcc_words
                    | cpp_words | polluted_words):
        return 'q_' + name
    return name


eatspace = '\033EATSPACE.'
pointer_suffix = ' *' + eatspace


def genindent(count):
    ret = ''
    for _ in range(count):
        ret += ' '
    return ret


indent_level = 0


def push_indent(indent_amount=4):
    global indent_level
    indent_level += indent_amount


def pop_indent(indent_amount=4):
    global indent_level
    indent_level -= indent_amount


# Generate @code with @kwds interpolated.
# Obey indent_level, and strip eatspace.
def cgen(code, **kwds):
    raw = code % kwds
    if indent_level:
        indent = genindent(indent_level)
        # re.subn() lacks flags support before Python 2.7, use re.compile()
        raw = re.subn(re.compile(r'^(?!(#|$))', re.MULTILINE),
                      indent, raw)
        raw = raw[0]
    return re.sub(re.escape(eatspace) + r' *', '', raw)


def mcgen(code, **kwds):
    if code[0] == '\n':
        code = code[1:]
    return cgen(code, **kwds)


def c_fname(filename):
    return re.sub(r'[^A-Za-z0-9_]', '_', filename)


def guardstart(name):
    return mcgen('''
#ifndef %(name)s
#define %(name)s

''',
                 name=c_fname(name).upper())


def guardend(name):
    return mcgen('''

#endif /* %(name)s */
''',
                 name=c_fname(name).upper())


def gen_if(ifcond):
    ret = ''
    for ifc in ifcond:
        ret += mcgen('''
#if %(cond)s
''', cond=ifc)
    return ret


def gen_endif(ifcond):
    ret = ''
    for ifc in reversed(ifcond):
        ret += mcgen('''
#endif /* %(cond)s */
''', cond=ifc)
    return ret


def _wrap_ifcond(ifcond, before, after):
    if before == after:
        return after   # suppress empty #if ... #endif

    assert after.startswith(before)
    out = before
    added = after[len(before):]
    if added[0] == '\n':
        out += '\n'
        added = added[1:]
    out += gen_if(ifcond)
    out += added
    out += gen_endif(ifcond)
    return out


def gen_enum_lookup(name, members, prefix=None):
    ret = mcgen('''

const QEnumLookup %(c_name)s_lookup = {
    .array = (const char *const[]) {
''',
                c_name=c_name(name))
    for m in members:
        ret += gen_if(m.ifcond)
        index = c_enum_const(name, m.name, prefix)
        ret += mcgen('''
        [%(index)s] = "%(name)s",
''',
                     index=index, name=m.name)
        ret += gen_endif(m.ifcond)

    ret += mcgen('''
    },
    .size = %(max_index)s
};
''',
                 max_index=c_enum_const(name, '_MAX', prefix))
    return ret


def gen_enum(name, members, prefix=None):
    # append automatically generated _MAX value
    enum_members = members + [QAPISchemaMember('_MAX')]

    ret = mcgen('''

typedef enum %(c_name)s {
''',
                c_name=c_name(name))

    for m in enum_members:
        ret += gen_if(m.ifcond)
        ret += mcgen('''
    %(c_enum)s,
''',
                     c_enum=c_enum_const(name, m.name, prefix))
        ret += gen_endif(m.ifcond)

    ret += mcgen('''
} %(c_name)s;
''',
                 c_name=c_name(name))

    ret += mcgen('''

#define %(c_name)s_str(val) \\
    qapi_enum_lookup(&%(c_name)s_lookup, (val))

extern const QEnumLookup %(c_name)s_lookup;
''',
                 c_name=c_name(name))
    return ret


def build_params(arg_type, boxed, extra=None):
    ret = ''
    sep = ''
    if boxed:
        assert arg_type
        ret += '%s arg' % arg_type.c_param_type()
        sep = ', '
    elif arg_type:
        assert not arg_type.variants
        for memb in arg_type.members:
            ret += sep
            sep = ', '
            if memb.optional:
                ret += 'bool has_%s, ' % c_name(memb.name)
            ret += '%s %s' % (memb.type.c_param_type(),
                              c_name(memb.name))
    if extra:
        ret += sep + extra
    return ret if ret else 'void'


#
# Accumulate and write output
#

class QAPIGen(object):

    def __init__(self, fname):
        self.fname = fname
        self._preamble = ''
        self._body = ''

    def preamble_add(self, text):
        self._preamble += text

    def add(self, text):
        self._body += text

    def get_content(self):
        return self._top() + self._preamble + self._body + self._bottom()

    def _top(self):
        return ''

    def _bottom(self):
        return ''

    def write(self, output_dir):
        pathname = os.path.join(output_dir, self.fname)
        dir = os.path.dirname(pathname)
        if dir:
            try:
                os.makedirs(dir)
            except os.error as e:
                if e.errno != errno.EEXIST:
                    raise
        fd = os.open(pathname, os.O_RDWR | os.O_CREAT, 0o666)
        if sys.version_info[0] >= 3:
            f = open(fd, 'r+', encoding='utf-8')
        else:
            f = os.fdopen(fd, 'r+')
        text = self.get_content()
        oldtext = f.read(len(text) + 1)
        if text != oldtext:
            f.seek(0)
            f.truncate(0)
            f.write(text)
        f.close()


@contextmanager
def ifcontext(ifcond, *args):
    """A 'with' statement context manager to wrap with start_if()/end_if()

    *args: any number of QAPIGenCCode

    Example::

        with ifcontext(ifcond, self._genh, self._genc):
            modify self._genh and self._genc ...

    Is equivalent to calling::

        self._genh.start_if(ifcond)
        self._genc.start_if(ifcond)
        modify self._genh and self._genc ...
        self._genh.end_if()
        self._genc.end_if()
    """
    for arg in args:
        arg.start_if(ifcond)
    yield
    for arg in args:
        arg.end_if()


class QAPIGenCCode(QAPIGen):

    def __init__(self, fname):
        QAPIGen.__init__(self, fname)
        self._start_if = None

    def start_if(self, ifcond):
        assert self._start_if is None
        self._start_if = (ifcond, self._body, self._preamble)

    def end_if(self):
        assert self._start_if
        self._wrap_ifcond()
        self._start_if = None

    def _wrap_ifcond(self):
        self._body = _wrap_ifcond(self._start_if[0],
                                  self._start_if[1], self._body)
        self._preamble = _wrap_ifcond(self._start_if[0],
                                      self._start_if[2], self._preamble)

    def get_content(self):
        assert self._start_if is None
        return QAPIGen.get_content(self)


class QAPIGenC(QAPIGenCCode):

    def __init__(self, fname, blurb, pydoc):
        QAPIGenCCode.__init__(self, fname)
        self._blurb = blurb
        self._copyright = '\n * '.join(re.findall(r'^Copyright .*', pydoc,
                                                  re.MULTILINE))

    def _top(self):
        return mcgen('''
/* AUTOMATICALLY GENERATED, DO NOT MODIFY */

/*
%(blurb)s
 *
 * %(copyright)s
 *
 * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
 * See the COPYING.LIB file in the top-level directory.
 */

''',
                     blurb=self._blurb, copyright=self._copyright)

    def _bottom(self):
        return mcgen('''

/* Dummy declaration to prevent empty .o file */
char qapi_dummy_%(name)s;
''',
                     name=c_fname(self.fname))


class QAPIGenH(QAPIGenC):

    def _top(self):
        return QAPIGenC._top(self) + guardstart(self.fname)

    def _bottom(self):
        return guardend(self.fname)


class QAPIGenDoc(QAPIGen):

    def _top(self):
        return (QAPIGen._top(self)
                + '@c AUTOMATICALLY GENERATED, DO NOT MODIFY\n\n')


class QAPISchemaMonolithicCVisitor(QAPISchemaVisitor):

    def __init__(self, prefix, what, blurb, pydoc):
        self._prefix = prefix
        self._what = what
        self._genc = QAPIGenC(self._prefix + self._what + '.c',
                              blurb, pydoc)
        self._genh = QAPIGenH(self._prefix + self._what + '.h',
                              blurb, pydoc)

    def write(self, output_dir):
        self._genc.write(output_dir)
        self._genh.write(output_dir)


class QAPISchemaModularCVisitor(QAPISchemaVisitor):

    def __init__(self, prefix, what, blurb, pydoc):
        self._prefix = prefix
        self._what = what
        self._blurb = blurb
        self._pydoc = pydoc
        self._genc = None
        self._genh = None
        self._module = {}
        self._main_module = None

    @staticmethod
    def _is_user_module(name):
        return name and not name.startswith('./')

    @staticmethod
    def _is_builtin_module(name):
        return not name

    def _module_dirname(self, what, name):
        if self._is_user_module(name):
            return os.path.dirname(name)
        return ''

    def _module_basename(self, what, name):
        ret = '' if self._is_builtin_module(name) else self._prefix
        if self._is_user_module(name):
            basename = os.path.basename(name)
            ret += what
            if name != self._main_module:
                ret += '-' + os.path.splitext(basename)[0]
        else:
            name = name[2:] if name else 'builtin'
            ret += re.sub(r'-', '-' + name + '-', what)
        return ret

    def _module_filename(self, what, name):
        return os.path.join(self._module_dirname(what, name),
                            self._module_basename(what, name))

    def _add_module(self, name, blurb):
        basename = self._module_filename(self._what, name)
        genc = QAPIGenC(basename + '.c', blurb, self._pydoc)
        genh = QAPIGenH(basename + '.h', blurb, self._pydoc)
        self._module[name] = (genc, genh)
        self._set_module(name)

    def _add_user_module(self, name, blurb):
        assert self._is_user_module(name)
        if self._main_module is None:
            self._main_module = name
        self._add_module(name, blurb)

    def _add_system_module(self, name, blurb):
        self._add_module(name and './' + name, blurb)

    def _set_module(self, name):
        self._genc, self._genh = self._module[name]

    def write(self, output_dir, opt_builtins=False):
        for name in self._module:
            if self._is_builtin_module(name) and not opt_builtins:
                continue
            (genc, genh) = self._module[name]
            genc.write(output_dir)
            genh.write(output_dir)

    def _begin_user_module(self, name):
        pass

    def visit_module(self, name):
        if name in self._module:
            self._set_module(name)
        elif self._is_builtin_module(name):
            # The built-in module has not been created.  No code may
            # be generated.
            self._genc = None
            self._genh = None
        else:
            self._add_user_module(name, self._blurb)
            self._begin_user_module(name)

    def visit_include(self, name, info):
        relname = os.path.relpath(self._module_filename(self._what, name),
                                  os.path.dirname(self._genh.fname))
        self._genh.preamble_add(mcgen('''
#include "%(relname)s.h"
''',
                                      relname=relname))