[PATCH 004/132] configure: integrate Meson in the build system

[Paolo Bonzini]

The Meson build system is integrated in the existing configure/make steps
by invoking Meson from the configure script and converting Meson's build.ninja
rules to an included Makefile.

Signed-off-by: Paolo Bonzini <address@hidden>
---
 Makefile             |    9 +
 configure            |   30 ++
 meson.build          |   19 +
 scripts/ninjatool.py | 1004 ++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 1062 insertions(+)
 create mode 100644 meson.build
 create mode 100755 scripts/ninjatool.py

diff --git a/Makefile b/Makefile
index e327df4..44daed6 100644
--- a/Makefile
+++ b/Makefile
@@ -52,6 +52,15 @@ git-submodule-update:
 endif
 endif
 
+export NINJA=./ninjatool
+Makefile.ninja: build.ninja ninjatool
+       ./ninjatool -t ninja2make --clean --omit dist uninstall < $< > $@
+-include Makefile.ninja
+
+ninjatool: ninjatool.stamp
+ninjatool.stamp: $(SRC_PATH)/scripts/ninjatool.py
+       $(MESON) setup --reconfigure . $(SRC_PATH) && touch $@
+
 .git-submodule-status: git-submodule-update config-host.mak
 
 # Check that we're not trying to do an out-of-tree build from
diff --git a/configure b/configure
index a444bc3..3e3eb3d 100755
--- a/configure
+++ b/configure
@@ -489,6 +489,7 @@ libxml2=""
 debug_mutex="no"
 libpmem=""
 default_devices="yes"
+meson=meson
 
 supported_cpu="no"
 supported_os="no"
@@ -952,6 +953,8 @@ for opt do
   ;;
   --python=*) python="$optarg"
   ;;
+  --meson=*) meson="$optarg"
+  ;;
   --gcov=*) gcov_tool="$optarg"
   ;;
   --smbd=*) smbd="$optarg"
@@ -1658,6 +1661,7 @@ Advanced options (experts only):
   --make=MAKE              use specified make [$make]
   --install=INSTALL        use specified install [$install]
   --python=PYTHON          use specified python [$python]
+  --meson=MESON            use specified meson [$meson]
   --smbd=SMBD              use specified smbd [$smbd]
   --with-git=GIT           use specified git [$git]
   --static                 enable static build [$static]
@@ -1823,6 +1827,12 @@ then
     error_exit "Python not found. Use --python=/path/to/python"
 fi
 
+if ! has "$meson"
+then
+    error_exit "Meson not found. Use --meson=/path/to/meson"
+fi
+meson=$(command -v $meson)
+
 # Note that if the Python conditional here evaluates True we will exit
 # with status 1 which is a shell 'false' value.
 if ! $python -c 'import sys; sys.exit(sys.version_info < (3,5))'; then
@@ -7266,6 +7276,7 @@ echo "INSTALL_PROG=$install -c -m 0755" >> 
$config_host_mak
 echo "INSTALL_LIB=$install -c -m 0644" >> $config_host_mak
 echo "PYTHON=$python" >> $config_host_mak
 echo "PYTHON_VERSION=$python_version" >> $config_host_mak
+echo "MESON=$meson" >> $config_host_mak
 echo "CC=$cc" >> $config_host_mak
 if $iasl -h > /dev/null 2>&1; then
   echo "IASL=$iasl" >> $config_host_mak
@@ -7841,6 +7852,25 @@ echo "# Automatically generated by configure - do not 
modify" > "$iotests_common
 echo >> "$iotests_common_env"
 echo "export PYTHON='$python'" >> "$iotests_common_env"
 
+rm -rf meson-private meson-info meson-logs
+NINJA=$PWD/ninjatool $python $meson setup \
+       --prefix "$prefix" \
+       --libdir "$libdir" \
+       --libexecdir "$libexecdir" \
+       --bindir "$bindir" \
+       --includedir "$includedir" \
+       --datadir "$datadir" \
+       --mandir "$mandir" \
+       --sysconfdir "$sysconfdir" \
+       --localstatedir "$local_statedir" \
+       $(test "$strip_opt" = yes && echo --strip) \
+       --buildtype $(if test "$debug" = yes; then echo debug; else echo 
debugoptimized; fi) \
+       "$PWD" "$source_path"
+
+if test "$?" -ne 0 ; then
+    error_exit "meson setup failed"
+fi
+
 # Save the configure command line for later reuse.
 cat <<EOD >config.status
 #!/bin/sh
diff --git a/meson.build b/meson.build
new file mode 100644
index 0000000..5491a6a
--- /dev/null
+++ b/meson.build
@@ -0,0 +1,19 @@
+project('qemu', ['c', 'cpp'], meson_version: '>=0.52.999')
+
+kconfig = import('unstable-kconfig')
+config_host = kconfig.load(meson.current_build_dir() / 'config-host.mak')
+
+add_project_arguments(config_host['CFLAGS'].split(),
+                      language: ['c', 'objc'])
+add_project_arguments(config_host['QEMU_CFLAGS'].split(),
+                      language: 'c')
+add_project_link_arguments(config_host['LDFLAGS'].split(),
+                           language: ['c', 'cpp', 'objc'])
+add_project_link_arguments(config_host['QEMU_LDFLAGS'].split(),
+                           language: ['c', 'cpp', 'objc'])
+add_project_arguments(config_host['QEMU_INCLUDES'].split(),
+                      language: 'c')
+
+configure_file(input: files('scripts/ninjatool.py'),
+               output: 'ninjatool',
+               configuration: config_host)
diff --git a/scripts/ninjatool.py b/scripts/ninjatool.py
new file mode 100755
index 0000000..a80b62f
--- /dev/null
+++ b/scripts/ninjatool.py
@@ -0,0 +1,1004 @@
+#! /bin/sh
+
+# Python module for parsing and processing .ninja files.
+#
+# Author: Paolo Bonzini
+#
+# Copyright (C) 2019 Red Hat, Inc.
+
+
+# We don't want to put "#! @PYTHON@" as the shebang and
+# make the file executable, so instead we make this a
+# Python/shell polyglot.  The first line below starts a
+# multiline string literal for Python, while it is just
+# ":" for bash.  The closing of the multiline string literal
+# is never parsed by bash since it exits before.
+
+'''':
+case "$0" in
+  /*) me=$0 ;;
+  *) me=$(command -v "$0") ;;
+esac
+python="@PYTHON@"
+case $python in
+  @*) python=python3 ;;
+esac
+exec $python "$me" "$@"
+exit 1
+'''
+
+
+from collections import namedtuple, defaultdict
+import sys
+import os
+import re
+import json
+import argparse
+
+
+class InvalidArgumentError(Exception):
+    pass
+
+
+# ---- lexer and parser ----
+
+BUILD = 1
+POOL = 2
+RULE = 3
+DEFAULT = 4
+EQUALS = 5
+COLON = 6
+PIPE = 7
+PIPE2 = 8
+IDENT = 9
+INCLUDE = 10
+INDENT = 11
+EOL = 12
+
+
+class LexerError(Exception):
+    pass
+
+
+class ParseError(Exception):
+    pass
+
+
+class NinjaParserEvents(object):
+    def __init__(self, parser):
+        self.parser = parser
+
+    def literal_token(self, word, in_path=False):
+        return word.replace('$', '$$')
+
+    def variable_expansion_token(self, varname):
+        return '${%s}' % varname
+
+    def tokens_to_arg(self, tokens):
+        return ''.join(tokens or [])
+
+    def variable(self, name, arg):
+        pass
+
+    def begin_file(self):
+        pass
+
+    def end_file(self):
+        pass
+
+    def end_scope(self):
+        pass
+
+    def begin_pool(self, name):
+        pass
+
+    def begin_rule(self, name):
+        pass
+
+    def begin_build(self, out, iout, rule, in_, iin, orderdep):
+        pass
+
+    def default(self, targets):
+        pass
+
+
+class NinjaParser(object):
+    PATH_RE = r"[^$\s:|]+|\$[$ :]|\$[a-zA-Z0-9_-]+|\$\{[a-zA-Z0-9_.-]+\}"
+    STRING_RE = r"(" + PATH_RE + r"|[\s:|])(?:\r?\n)?"
+    TOPLEVEL_RE = r"([=:#]|\|\|?|^ +|(?:" + PATH_RE + r")+)\s*"
+    IDENT_RE = r"[a-zA-Z0-9_.-]+$"
+
+    InputFile = namedtuple('InputFile', 'filename iter lineno')
+
+    def __init__(self, filename, input):
+        self.stack = []
+        self.lineno = None
+        self.match_keyword = True
+        self.push(filename, input)
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        while len(self.stack):
+            try:
+                return next(self.stack[-1].iter)
+            except StopIteration:
+                self.pop()
+        raise StopIteration
+
+    def push(self, filename, input):
+        entered = self.InputFile(filename=filename or 'stdin',
+                                 iter=self._tokens(input),
+                                 lineno=self.lineno)
+        self.stack.append(entered)
+        self.lineno = 0
+        if filename is not None:
+            os.chdir(os.path.dirname(filename) or '.')
+
+    def pop(self):
+        left = self.stack.pop()
+        self.lineno = left.lineno
+        if len(self.stack):
+            os.chdir(os.path.dirname(self.stack[-1].filename) or '.')
+
+    def next_line(self, input):
+        line = next(input).rstrip()
+        self.lineno += 1
+        while len(line) and line[-1] == '$':
+            line = line[0:-1] + next(input).strip()
+            self.lineno += 1
+        return line
+
+    def print_token(self, tok):
+        if tok == EOL:
+            return "end of line"
+        if tok == BUILD:
+            return '"build"'
+        if tok == POOL:
+            return '"pool"'
+        if tok == RULE:
+            return '"rule"'
+        if tok == DEFAULT:
+            return '"default"'
+        if tok == EQUALS:
+            return '"="'
+        if tok == COLON:
+            return '":"'
+        if tok == PIPE:
+            return '"|"'
+        if tok == PIPE2:
+            return '"||"'
+        if tok == INCLUDE:
+            return '"include"'
+        if tok == IDENT:
+            return 'identifier'
+        return '"%s"' % tok
+
+    def error(self, msg):
+        raise LexerError("%s:%d: %s" % (self.stack[-1].filename, self.lineno, 
msg))
+
+    def parse_error(self, msg):
+        raise ParseError("%s:%d: %s" % (self.stack[-1].filename, self.lineno, 
msg))
+
+    def expected(self, expected, tok):
+        msg = "found %s, expected " % (self.print_token(tok), )
+        for i, exp_tok in enumerate(expected):
+            if i > 0:
+                msg = msg + (' or ' if i == len(expected) - 1 else ', ')
+            msg = msg + self.print_token(exp_tok)
+        self.parse_error(msg)
+
+    def find_tokens(self, regex, line):
+        # group 1 is used to distinguish expected input from bad characters
+        # group 2, which is really group 1 in regex, is returned
+        for m in re.finditer("(" + regex + ")|.", line):
+            if not m.group(1):
+                self.error("unexpected '%s'" % (m.group(0), ))
+            if m.group(2):
+                yield m.span(), m.group(2)
+
+    def _variable_tokens(self, value):
+        for span, match in self.find_tokens(self.STRING_RE, value):
+            yield match
+
+    def _tokens(self, input):
+        while True:
+            try:
+                line = self.next_line(input)
+            except StopIteration:
+                return
+            for span, match in self.find_tokens(self.TOPLEVEL_RE, line):
+                if match == ':':
+                    yield COLON
+                    continue
+                if match == '|':
+                    yield PIPE
+                    continue
+                if match == '||':
+                    yield PIPE2
+                    continue
+                if match[0] == ' ':
+                    yield INDENT
+                    continue
+                if match[0] == '=':
+                    value = line[span[0] + 1:].lstrip()
+                    yield EQUALS
+                    yield from self._variable_tokens(value)
+                    break
+                if match[0] == '#':
+                    break
+
+                # identifier
+                if self.match_keyword:
+                    if match == 'build':
+                        yield BUILD
+                        continue
+                    if match == 'pool':
+                        yield POOL
+                        continue
+                    if match == 'rule':
+                        yield RULE
+                        continue
+                    if match == 'default':
+                        yield DEFAULT
+                        continue
+                    if match == 'include':
+                        filename = line[span[0] + 8:].strip()
+                        self.push(filename, open(filename, 'r'))
+                        break
+                    if match == 'subninja':
+                        self.error('subninja is not supported')
+                yield match
+            yield EOL
+
+    def read_ident(self):
+        """Read an identifier, where the only allowed characters are
+           letter, numbers, dash, period and underscore."""
+        self.match_keyword = False
+        token = self.__next__()
+        self.match_keyword = True
+        if isinstance(token, str) and not re.match(self.IDENT_RE, token):
+            self.parse_error('variable expansion not allowed')
+        return token
+
+    def read_path(self):
+        """Read a space-delimited path or a non-alphanumeric token, and
+           return a generator that produces either the token alone, or
+           the components of the path (identifiers and variable expansions)."""
+        self.match_keyword = False
+        token = self.__next__()
+        self.match_keyword = True
+        if isinstance(token, str):
+            yield from self._variable_tokens(token)
+        else:
+            yield token
+
+    def parse(self, events):
+        global_var = True
+
+        def advance():
+            try:
+                return next(self)
+            except StopIteration:
+                return None
+
+        def look_for(*expected):
+            tok = advance()
+            if tok in expected:
+                return tok
+            self.expected(expected, tok)
+
+        def look_for_ident(*expected):
+            try:
+                tok = self.read_ident()
+            except StopIteration:
+                tok = None
+            if isinstance(tok, str) or tok in expected:
+                return tok
+            self.expected(expected + (IDENT,), tok)
+
+        def parse_assignment_rhs(gen, expected, in_path):
+            value = []
+            for tok in gen:
+                if not isinstance(tok, str):
+                    if tok in expected:
+                        break
+                    self.expected(expected + (IDENT,), tok)
+                if tok[0] != '$':
+                    value.append(events.literal_token(tok, in_path))
+                elif tok == '$ ' or tok == '$$' or tok == '$:':
+                    value.append(events.literal_token(tok[1], in_path))
+                else:
+                    var = tok[2:-1] if tok[1] == '{' else tok[1:]
+                    value.append(events.variable_expansion_token(var))
+            else:
+                # gen must have raised StopIteration, return None
+                # for consistency with advance()
+                tok = None
+            value = value if len(value) else None
+            return value, tok
+
+        def look_for_path(*expected):
+            # paths in build rules are parsed one space-separated token
+            # at a time and expanded
+            gen = self.read_path()
+            value, tok = parse_assignment_rhs(gen, expected, True)
+            return value, tok
+
+        def parse_assignment(tok):
+            assert isinstance(tok, str)
+            look_for(EQUALS)
+            name = tok
+            value, tok = parse_assignment_rhs(self, (EOL,), False)
+            assert tok == EOL
+            events.variable(name, events.tokens_to_arg(value))
+
+        def parse_build():
+            # parse outputs
+            out = []
+            iout = []
+            while True:
+                value, tok = look_for_path(COLON, PIPE)
+                if value is None:
+                    break
+                out.append(events.tokens_to_arg(value))
+            if tok == PIPE:
+                while True:
+                    value, tok = look_for_path(COLON)
+                    if value is None:
+                        break
+                    iout.append(events.tokens_to_arg(value))
+
+            # parse rule
+            assert tok == COLON
+            rule = look_for_ident()
+
+            # parse inputs and dependencies
+            in_ = []
+            iin = []
+            orderdep = []
+            while True:
+                value, tok = look_for_path(PIPE, PIPE2, EOL)
+                if value is None:
+                    break
+                in_.append(events.tokens_to_arg(value))
+            if tok == PIPE:
+                while True:
+                    value, tok = look_for_path(PIPE2, EOL)
+                    if value is None:
+                        break
+                    iin.append(events.tokens_to_arg(value))
+            if tok == PIPE2:
+                while True:
+                    value, tok = look_for_path(EOL)
+                    if value is None:
+                        break
+                    orderdep.append(events.tokens_to_arg(value))
+            assert tok == EOL
+            events.begin_build(out, iout, rule, in_, iin, orderdep)
+            nonlocal global_var
+            global_var = False
+
+        def parse_pool():
+            # pool declarations are ignored.  Just gobble all the variables
+            ident = look_for_ident()
+            look_for(EOL)
+            events.begin_pool(ident)
+            nonlocal global_var
+            global_var = False
+
+        def parse_rule():
+            ident = look_for_ident()
+            look_for(EOL)
+            events.begin_rule(ident)
+            nonlocal global_var
+            global_var = False
+
+        def parse_default():
+            idents = []
+            while True:
+                ident = look_for_ident(EOL)
+                if ident == EOL:
+                    break
+                idents.append(ident)
+            events.default(idents)
+
+        def parse_declaration(tok):
+            if tok == EOL:
+                return
+
+            nonlocal global_var
+            if tok == INDENT:
+                if global_var:
+                    self.parse_error('indented line outside rule or edge')
+                tok = look_for_ident(EOL)
+                if tok == EOL:
+                    return
+                parse_assignment(tok)
+                return
+
+            if not global_var:
+                events.end_scope()
+                global_var = True
+            if not tok:
+                return
+            if tok == POOL:
+                parse_pool()
+            elif tok == BUILD:
+                parse_build()
+            elif tok == RULE:
+                parse_rule()
+            elif tok == DEFAULT:
+                parse_default()
+            elif isinstance(tok, str):
+                parse_assignment(tok)
+            else:
+                self.expected((POOL, BUILD, RULE, INCLUDE, DEFAULT, IDENT), 
tok)
+
+        events.begin_file()
+        while True:
+            tok = advance()
+            parse_declaration(tok)
+            if not tok:
+                break
+        events.end_file()
+
+
+# ---- variable handling ----
+
+def expand(x, rule_vars=None, build_vars=None, global_vars=None):
+    if x is None:
+        return None
+    changed = True
+    while changed:
+        changed = False
+        matches = list(re.finditer(r'\$\$|\$\{([^}]*)\}', x))
+        if not matches:
+            break
+
+        # Reverse the match so that expanding later matches does not
+        # invalidate m.span() for earlier ones.  Do not reduce $$ to $
+        # until all variables are dealt with.
+        matches.reverse()
+        for m in matches:
+            if not m.group(1):
+                continue
+            changed = True
+            name = m.group(1)
+            if build_vars and name in build_vars:
+                value = build_vars[name]
+            elif rule_vars and name in rule_vars:
+                value = rule_vars[name]
+            elif name in global_vars:
+                value = global_vars[name]
+            else:
+                value = ''
+            start, end = m.span()
+            x = x[:start] + value + x[end:]
+    return x.replace('$$', '$')
+
+
+class Scope(object):
+    def __init__(self, events):
+        self.events = events
+
+    def on_left_scope(self):
+        pass
+
+    def on_variable(self, key, value):
+        pass
+
+
+class BuildScope(Scope):
+    def __init__(self, events, out, iout, rule, in_, iin, orderdep, rule_vars):
+        super().__init__(events)
+        self.rule = rule
+        self.out = [events.expand_and_normalize(x) for x in out]
+        self.in_ = [events.expand_and_normalize(x) for x in in_]
+        self.iin = [events.expand_and_normalize(x) for x in iin]
+        self.orderdep = [events.expand_and_normalize(x) for x in orderdep]
+        self.iout = [events.expand_and_normalize(x) for x in iout]
+        self.rule_vars = rule_vars
+        self.build_vars = dict()
+        self._define_variable('out', ' '.join(self.out))
+        self._define_variable('in', ' '.join(self.in_))
+
+    def expand(self, x):
+        return self.events.expand(x, self.rule_vars, self.build_vars)
+
+    def on_left_scope(self):
+        self.events.variable('out', self.build_vars['out'])
+        self.events.variable('in', self.build_vars['in'])
+        self.events.end_build(self, self.out, self.iout, self.rule, self.in_,
+                              self.iin, self.orderdep)
+
+    def _define_variable(self, key, value):
+        # The value has been expanded already, quote it for further
+        # expansion from rule variables
+        value = value.replace('$', '$$')
+        self.build_vars[key] = value
+
+    def on_variable(self, key, value):
+        # in and out are at the top of the lookup order and cannot
+        # be overridden.  Also, unlike what the manual says, build
+        # variables only lookup global variables.  They never lookup
+        # rule variables, earlier build variables, or in/out.
+        if key not in ('in', 'in_newline', 'out'):
+            self._define_variable(key, self.events.expand(value))
+
+
+class RuleScope(Scope):
+    def __init__(self, events, name, vars_dict):
+        super().__init__(events)
+        self.name = name
+        self.vars_dict = vars_dict
+        self.generator = False
+
+    def on_left_scope(self):
+        self.events.end_rule(self, self.name)
+
+    def on_variable(self, key, value):
+        self.vars_dict[key] = value
+        if key == 'generator':
+            self.generator = True
+
+
+class NinjaParserEventsWithVars(NinjaParserEvents):
+    def __init__(self, parser):
+        super().__init__(parser)
+        self.rule_vars = defaultdict(lambda: dict())
+        self.global_vars = dict()
+        self.scope = None
+
+    def variable(self, name, value):
+        if self.scope:
+            self.scope.on_variable(name, value)
+        else:
+            self.global_vars[name] = self.expand(value)
+
+    def begin_build(self, out, iout, rule, in_, iin, orderdep):
+        if rule != 'phony' and rule not in self.rule_vars:
+            self.parser.parse_error("undefined rule '%s'" % rule)
+
+        self.scope = BuildScope(self, out, iout, rule, in_, iin, orderdep, 
self.rule_vars[rule])
+
+    def begin_pool(self, name):
+        # pool declarations are ignored.  Just gobble all the variables
+        self.scope = Scope(self)
+
+    def begin_rule(self, name):
+        if name in self.rule_vars:
+            self.parser.parse_error("duplicate rule '%s'" % name)
+        self.scope = RuleScope(self, name, self.rule_vars[name])
+
+    def end_scope(self):
+        self.scope.on_left_scope()
+        self.scope = None
+
+    # utility functions:
+
+    def expand(self, x, rule_vars=None, build_vars=None):
+        return expand(x, rule_vars, build_vars, self.global_vars)
+
+    def expand_and_normalize(self, x):
+        return os.path.normpath(self.expand(x))
+
+    # extra events not present in the superclass:
+
+    def end_build(self, scope, out, iout, rule, in_, iin, orderdep):
+        pass
+
+    def end_rule(self, scope, name):
+        pass
+
+
+# ---- test client that just prints back whatever it parsed  ----
+
+class Writer(NinjaParserEvents):
+    ARGS = argparse.ArgumentParser(description='Rewrite input build.ninja to 
stdout.')
+
+    def __init__(self, output, parser, args):
+        super().__init__(parser)
+        self.output = output
+        self.indent = ''
+        self.had_vars = False
+
+    def literal_token(self, word, in_path=False):
+        word = word.replace('$', '$$')
+        if in_path:
+            word = word.replace(' ', '$ ').replace(':', '$:')
+        return word
+
+    def print(self, *args, **kwargs):
+        if len(args):
+            self.output.write(self.indent)
+        print(*args, **kwargs, file=self.output)
+
+    def variable(self, name, value):
+        self.print('%s = %s' % (name, value))
+        self.had_vars = True
+
+    def begin_scope(self):
+        self.indent = '  '
+        self.had_vars = False
+
+    def end_scope(self):
+        if self.had_vars:
+            self.print()
+        self.indent = ''
+        self.had_vars = False
+
+    def begin_pool(self, name):
+        self.print('pool %s' % name)
+        self.begin_scope()
+
+    def begin_rule(self, name):
+        self.print('rule %s' % name)
+        self.begin_scope()
+
+    def begin_build(self, outputs, implicit_outputs, rule, inputs, implicit, 
order_only):
+        all_outputs = list(outputs)
+        all_inputs = list(inputs)
+
+        if implicit:
+            all_inputs.append('|')
+            all_inputs.extend(implicit)
+        if order_only:
+            all_inputs.append('||')
+            all_inputs.extend(order_only)
+        if implicit_outputs:
+            all_outputs.append('|')
+            all_outputs.extend(implicit_outputs)
+
+        self.print('build %s: %s' % (' '.join(all_outputs),
+                                     ' '.join([rule] + all_inputs)))
+        self.begin_scope()
+
+    def default(self, targets):
+        self.print('default %s' % ' '.join(targets))
+
+
+# ---- emit compile_commands.json ----
+
+class Compdb(NinjaParserEventsWithVars):
+    ARGS = argparse.ArgumentParser(description='Emit compile_commands.json.')
+    ARGS.add_argument('rules', nargs='*',
+                      help='The ninja rules to emit compilation commands for.')
+
+    def __init__(self, output, parser, args):
+        super().__init__(parser)
+        self.output = output
+        self.rules = args.rules
+        self.sep = ''
+
+    def begin_file(self):
+        self.output.write('[')
+        self.directory = os.getcwd()
+
+    def print_entry(self, **entry):
+        entry['directory'] = self.directory
+        self.output.write(self.sep + json.dumps(entry))
+        self.sep = ',\n'
+
+    def begin_build(self, out, iout, rule, in_, iin, orderdep):
+        if in_ and rule in self.rules:
+            super().begin_build(out, iout, rule, in_, iin, orderdep)
+        else:
+            self.scope = Scope(self)
+
+    def end_build(self, scope, out, iout, rule, in_, iin, orderdep):
+        self.print_entry(command=scope.expand('${command}'), file=in_[0])
+
+    def end_file(self):
+        self.output.write(']\n')
+
+
+# ---- clean output files ----
+
+class Clean(NinjaParserEventsWithVars):
+    ARGS = argparse.ArgumentParser(description='Remove output build files.')
+    ARGS.add_argument('-g', dest='generator', action='store_true',
+                      help='clean generated files too')
+
+    def __init__(self, output, parser, args):
+        super().__init__(parser)
+        self.dry_run = args.dry_run
+        self.verbose = args.verbose or args.dry_run
+        self.generator = args.generator
+
+    def begin_file(self):
+        print('Cleaning... ', end=(None if self.verbose else ''), flush=True)
+        self.cnt = 0
+
+    def end_file(self):
+        print('%d files' % self.cnt)
+
+    def do_clean(self, *files):
+        for f in files:
+            if self.dry_run:
+                if os.path.exists(f):
+                    self.cnt += 1
+                    print('Would remove ' + f)
+                    continue
+            else:
+                try:
+                    os.unlink(f)
+                    self.cnt += 1
+                    if self.verbose:
+                        print('Removed ' + f)
+                except FileNotFoundError:
+                    pass
+
+    def end_build(self, scope, out, iout, rule, in_, iin, orderdep):
+        if rule == 'phony':
+            return
+        if not self.generator and scope.expand('${generator}'):
+            return
+        self.do_clean(*out, *iout)
+        depfile = scope.expand('${depfile}')
+        if depfile:
+            self.do_clean(depfile)
+
+
+# ---- convert build.ninja to makefile ----
+
+class Ninja2Make(NinjaParserEventsWithVars):
+    ARGS = argparse.ArgumentParser(description='Convert build.ninja to a 
Makefile.')
+    ARGS.add_argument('--clean', dest='emit_clean', action='store_true',
+                      help='Emit clean/distclean rules.')
+    ARGS.add_argument('--doublecolon', action='store_true',
+                      help='Emit double-colon rules for phony targets.')
+    ARGS.add_argument('--omit', metavar='TARGET', nargs='+',
+                      help='Targets to omit.')
+
+    def __init__(self, output, parser, args):
+        super().__init__(parser)
+        self.output = output
+
+        self.emit_clean = args.emit_clean
+        self.doublecolon = args.doublecolon
+        self.omit = set(args.omit)
+
+        if self.emit_clean:
+            self.omit.update(['clean', 'distclean'])
+
+        # Lists of targets are kept in memory and emitted only at the
+        # end because appending is really inefficient in GNU make.
+        # We only do it when it's O(#rules) or O(#variables), but
+        # never when it could be O(#targets).
+        self.depfiles = list()
+        self.build_vars = defaultdict(lambda: dict())
+        self.rule_targets = defaultdict(lambda: list())
+        self.num_stamp = defaultdict(lambda: 0)
+        self.all_outs = set()
+        self.all_ins = set()
+        self.all_phony = set()
+        self.seen_default = False
+
+    def print(self, *args, **kwargs):
+        print(*args, **kwargs, file=self.output)
+
+    def literal_token(self, word, in_path=False):
+        if in_path and ' ' in word:
+            self.parser.parse_error('Make does not support spaces in 
filenames')
+        return word.replace('$', '$$')
+
+    def print_phony(self, outs, ins):
+        targets = ' '.join(outs).replace('$', '$$')
+        deps = ' '.join(ins).replace('$', '$$')
+        deps = deps.strip()
+        if self.doublecolon:
+            self.print(targets + '::' + (' ' if deps else '') + deps + ';@:')
+        else:
+            self.print(targets + ':' + (' ' if deps else '') + deps)
+        self.all_phony.update(outs)
+
+    def begin_file(self):
+        self.print(r'# This is an automatically generated file, and it shows.')
+        self.print(r'ninja-default:')
+        self.print(r'.PHONY: ninja-default')
+        if self.emit_clean:
+            self.print(r'ninja-clean:: ninja-clean-start; $(if $V,,@)rm -f 
${ninja-depfiles}')
+            self.print(r'ninja-clean-start:; $(if $V,,@echo Cleaning...)')
+            self.print(r'ninja-distclean:: clean')
+            self.print(r'.PHONY: ninja-clean ninja-clean-start 
ninja-distclean')
+            self.print_phony(['clean'], ['ninja-clean'])
+            self.print_phony(['distclean'], ['ninja-distclean'])
+        self.print(r'vpath')
+        self.print(r'NULL :=')
+        self.print(r'SPACE := ${NULL} #')
+        self.print(r'MAKEFLAGS += -rR')
+        self.print(r'define NEWLINE')
+        self.print(r'')
+        self.print(r'endef')
+        self.print(r'.var.in_newline = $(subst 
$(SPACE),$(NEWLINE),${.var.in})')
+        self.print(r"ninja-command = $(if $V,,$(if ${.var.description},@printf 
'%s\n' '$(subst ','\'',${.var.description})' && ))${.var.command}")
+        self.print(r"ninja-command-restat = $(if $V,,$(if 
${.var.description},@printf '%s\n' '$(subst ','\'',${.var.description})' && 
))${.var.command} && if test -f $(firstword ${.var.out}); then printf '%s\n' 
${.var.out} > $@; fi")
+
+    def mangle_vars_for_make(self, x):
+        matches = list(re.finditer(r'\$\$|\$\{([^}]*)\}', x))
+
+        # Reverse the match so that expanding later matches does not
+        # invalidate m.span() for earlier ones.
+        matches.reverse()
+        for m in matches:
+            if not m.group(1):
+                continue
+            value = '${.var.' + m.group(1) + '}'
+            start, end = m.span()
+            x = x[:start] + value + x[end:]
+        return x
+
+    def end_file(self):
+        def natural_sort_key(s, _nsre=re.compile('([0-9]+)')):
+            return [int(text) if text.isdigit() else text.lower()
+                    for text in _nsre.split(s)]
+
+        self.print()
+        self.print('ninja-outputdirs :=')
+        for rule in self.rule_vars:
+            if rule == 'phony':
+                continue
+            self.print('ninja-targets-%s := %s' % (rule, ' 
'.join(self.rule_targets[rule])))
+            for name, value in self.rule_vars[rule].items():
+                self.print('$(ninja-targets-%s): .var.%s = %s' % (rule, name, 
self.mangle_vars_for_make(value)))
+            self.print('ninja-outputdirs += $(sort $(dir 
${ninja-targets-%s}))' % rule)
+            self.print()
+        self.print('dummy := $(shell mkdir -p . $(sort $(ninja-outputdirs)))')
+        self.print('ninja-depfiles :=' + ' '.join(self.depfiles))
+        self.print('-include ${ninja-depfiles}')
+        self.print()
+        for targets in self.build_vars:
+            for name, value in self.build_vars[targets].items():
+                self.print('%s: .var.%s := %s' % (targets, name, value))
+            self.print()
+        if not self.seen_default:
+            default_targets = sorted(self.all_outs - self.all_ins, 
key=natural_sort_key)
+            self.print('ninja-default: ' + ' '.join(default_targets))
+
+        # This is a hack...  Meson declares input meson.build files as
+        # phony, because Ninja does not have an equivalent of Make's
+        # "path/to/file:" declaration that ignores "path/to/file" even
+        # if it is absent.  However, Makefile.ninja wants to depend on
+        # build.ninja, which in turn depends on these phony targets which
+        # would cause Makefile.ninja to be rebuilt in a loop.
+        phony_targets = sorted(self.all_phony - self.all_ins, 
key=natural_sort_key)
+        self.print('.PHONY: ' + ' '.join(phony_targets))
+
+    def variable(self, name, value):
+        super().variable(name, value)
+        if self.scope is None:
+            self.global_vars[name] = self.expand(value)
+            self.print('.var.%s := %s' % (name, self.global_vars[name]))
+
+    def begin_build(self, out, iout, rule, in_, iin, orderdep):
+        if any(x in self.omit for x in out):
+            self.scope = Scope(self)
+            return
+
+        super().begin_build(out, iout, rule, in_, iin, orderdep)
+        self.current_targets = ' '.join(self.scope.out + 
self.scope.iout).replace('$', '$$')
+
+    def end_build(self, scope, out, iout, rule, in_, iin, orderdep):
+        self.rule_targets[rule] += self.scope.out
+        self.rule_targets[rule] += self.scope.iout
+
+        self.all_outs.update(self.scope.iout)
+        self.all_outs.update(self.scope.out)
+        self.all_ins.update(self.scope.in_)
+        self.all_ins.update(self.scope.iin)
+
+        targets = self.current_targets
+        self.current_targets = None
+        if rule == 'phony':
+            # Phony rules treat order-only dependencies as normal deps
+            self.print_phony(out + iout, in_ + iin + orderdep)
+            return
+
+        inputs = ' '.join(in_ + iin).replace('$', '$$')
+        orderonly = ' '.join(orderdep).replace('$', '$$')
+        restat = 'restat' in self.scope.build_vars or 'restat' in 
self.rule_vars[rule]
+        if restat:
+            if len(out) == 1:
+                stamp = out[0] + '.stamp'
+            else:
+                stamp = '%s%d.stamp' %(rule, self.num_stamp[rule])
+                self.num_stamp[rule] += 1
+            self.print('%s: %s' % (targets, stamp))
+            self.print('%s: %s | %s; ${ninja-command-restat}' % (stamp, 
inputs, orderonly))
+            self.rule_targets[rule].append(stamp)
+            self.build_vars[stamp] = self.scope.build_vars
+        else:
+            self.print('%s: %s | %s; ${ninja-command}' % (targets, inputs, 
orderonly))
+            self.build_vars[targets] = self.scope.build_vars
+
+        depfile = scope.expand('${depfile}')
+        if depfile:
+            self.depfiles.append(depfile)
+
+    def end_rule(self, scope, name):
+        if self.emit_clean:
+            # Note that the generator pseudo-variable could also be attached
+            # to a build block rather than a rule.  This is not handled here
+            # in order to reduce the number of "rm" invocations.  However,
+            # "ninjatool.py -t clean" does that correctly.
+            self.print('ninja-%s:: ; $(if $V,,@)rm -f ${ninja-targets-%s}' % (
+                'distclean' if scope.generator else 'clean',
+                name))
+
+    def default(self, targets):
+        self.print("ninja-default: " + ' '.join(targets))
+        self.seen_default = True
+
+
+# ---- command line parsing ----
+
+# we cannot use subparsers because tools are chosen through the "-t"
+# option.
+
+class ToolAction(argparse.Action):
+    def __init__(self, option_strings, dest, choices, metavar='TOOL', 
nargs=None, **kwargs):
+        if nargs is not None:
+            raise ValueError("nargs not allowed")
+        super().__init__(option_strings, dest, required=True, choices=choices,
+                         metavar=metavar, **kwargs)
+
+    def __call__(self, parser, namespace, value, option_string):
+        tool = self.choices[value]
+        setattr(namespace, self.dest, tool)
+        tool.ARGS.prog = '%s %s %s' % (parser.prog, option_string, value)
+
+
+class ToolHelpAction(argparse.Action):
+    def __init__(self, option_strings, dest, nargs=None, **kwargs):
+        if nargs is not None:
+            raise ValueError("nargs not allowed")
+        super().__init__(option_strings, dest, nargs=0, **kwargs)
+
+    def __call__(self, parser, namespace, values, option_string=None):
+        if namespace.tool:
+            namespace.tool.ARGS.print_help()
+        else:
+            parser.print_help()
+        parser.exit()
+
+
+tools = {
+    'test': Writer,
+    'ninja2make': Ninja2Make,
+    'compdb': Compdb,
+    'clean': Clean,
+}
+
+parser = argparse.ArgumentParser(description='Process and transform 
build.ninja files.',
+                                 add_help=False)
+parser.add_argument('-C', metavar='DIR', dest='dir', default='.',
+                    help='change to DIR before doing anything else')
+parser.add_argument('-f', metavar='FILE', dest='file', default='build.ninja',
+                    help='specify input build file [default=build.ninja]')
+parser.add_argument('-n', dest='dry_run', action='store_true',
+                    help='do not actually do anything')
+parser.add_argument('-v', dest='verbose', action='store_true',
+                    help='be more verbose')
+
+parser.add_argument('-t', dest='tool', choices=tools, action=ToolAction,
+                    help='choose the tool to run')
+parser.add_argument('-h', '--help', action=ToolHelpAction,
+                    help='show this help message and exit')
+
+if len(sys.argv) >= 2 and sys.argv[1] == '--version':
+    print('1.8')
+    sys.exit(0)
+
+args, tool_args = parser.parse_known_args()
+args.tool.ARGS.parse_args(tool_args, args)
+
+os.chdir(args.dir)
+with open(args.file, 'r') as f:
+    parser = NinjaParser(args.file, f)
+    try:
+        events = args.tool(sys.stdout, parser, args)
+    except InvalidArgumentError as e:
+        parser.error(str(e))
+    parser.parse(events)
-- 
1.8.3.1