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#! /usr/bin/python3
# Approximation to C preprocessing.
# Copyright (C) 2019-2022 Free Software Foundation, Inc.
# This file is part of the GNU C Library.
#
# The GNU C Library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# The GNU C Library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with the GNU C Library; if not, see
# <https://www.gnu.org/licenses/>.
"""
Simplified lexical analyzer for C preprocessing tokens.
Does not implement trigraphs.
Does not implement backslash-newline in the middle of any lexical
item other than a string literal.
Does not implement universal-character-names in identifiers.
Treats prefixed strings (e.g. L"...") as two tokens (L and "...").
Accepts non-ASCII characters only within comments and strings.
"""
import collections
import re
# Caution: The order of the outermost alternation matters.
# STRING must be before BAD_STRING, CHARCONST before BAD_CHARCONST,
# BLOCK_COMMENT before BAD_BLOCK_COM before PUNCTUATOR, and OTHER must
# be last.
# Caution: There should be no capturing groups other than the named
# captures in the outermost alternation.
# For reference, these are all of the C punctuators as of C11:
# [ ] ( ) { } , ; ? ~
# ! != * *= / /= ^ ^= = ==
# # ##
# % %= %> %: %:%:
# & &= &&
# | |= ||
# + += ++
# - -= -- ->
# . ...
# : :>
# < <% <: << <<= <=
# > >= >> >>=
# The BAD_* tokens are not part of the official definition of pp-tokens;
# they match unclosed strings, character constants, and block comments,
# so that the regex engine doesn't have to backtrack all the way to the
# beginning of a broken construct and then emit dozens of junk tokens.
PP_TOKEN_RE_ = re.compile(r"""
(?P<STRING> \"(?:[^\"\\\r\n]|\\(?:[\r\n -~]|\r\n))*\")
|(?P<BAD_STRING> \"(?:[^\"\\\r\n]|\\[ -~])*)
|(?P<CHARCONST> \'(?:[^\'\\\r\n]|\\(?:[\r\n -~]|\r\n))*\')
|(?P<BAD_CHARCONST> \'(?:[^\'\\\r\n]|\\[ -~])*)
|(?P<BLOCK_COMMENT> /\*(?:\*(?!/)|[^*])*\*/)
|(?P<BAD_BLOCK_COM> /\*(?:\*(?!/)|[^*])*\*?)
|(?P<LINE_COMMENT> //[^\r\n]*)
|(?P<IDENT> [_a-zA-Z][_a-zA-Z0-9]*)
|(?P<PP_NUMBER> \.?[0-9](?:[0-9a-df-oq-zA-DF-OQ-Z_.]|[eEpP][+-]?)*)
|(?P<PUNCTUATOR>
[,;?~(){}\[\]]
| [!*/^=]=?
| \#\#?
| %(?:[=>]|:(?:%:)?)?
| &[=&]?
|\|[=|]?
|\+[=+]?
| -[=->]?
|\.(?:\.\.)?
| :>?
| <(?:[%:]|<(?:=|<=?)?)?
| >(?:=|>=?)?)
|(?P<ESCNL> \\(?:\r|\n|\r\n))
|(?P<WHITESPACE> [ \t\n\r\v\f]+)
|(?P<OTHER> .)
""", re.DOTALL | re.VERBOSE)
HEADER_NAME_RE_ = re.compile(r"""
< [^>\r\n]+ >
| " [^"\r\n]+ "
""", re.DOTALL | re.VERBOSE)
ENDLINE_RE_ = re.compile(r"""\r|\n|\r\n""")
# based on the sample code in the Python re documentation
Token_ = collections.namedtuple("Token", (
"kind", "text", "line", "column", "context"))
Token_.__doc__ = """
One C preprocessing token, comment, or chunk of whitespace.
'kind' identifies the token type, which will be one of:
STRING, CHARCONST, BLOCK_COMMENT, LINE_COMMENT, IDENT,
PP_NUMBER, PUNCTUATOR, ESCNL, WHITESPACE, HEADER_NAME,
or OTHER. The BAD_* alternatives in PP_TOKEN_RE_ are
handled within tokenize_c, below.
'text' is the sequence of source characters making up the token;
no decoding whatsoever is performed.
'line' and 'column' give the position of the first character of the
token within the source file. They are both 1-based.
'context' indicates whether or not this token occurred within a
preprocessing directive; it will be None for running text,
'<null>' for the leading '#' of a directive line (because '#'
all by itself on a line is a "null directive"), or the name of
the directive for tokens within a directive line, starting with
the IDENT for the name itself.
"""
def tokenize_c(file_contents, reporter):
"""Yield a series of Token objects, one for each preprocessing
token, comment, or chunk of whitespace within FILE_CONTENTS.
The REPORTER object is expected to have one method,
reporter.error(token, message), which will be called to
indicate a lexical error at the position of TOKEN.
If MESSAGE contains the four-character sequence '{!r}', that
is expected to be replaced by repr(token.text).
"""
Token = Token_
PP_TOKEN_RE = PP_TOKEN_RE_
ENDLINE_RE = ENDLINE_RE_
HEADER_NAME_RE = HEADER_NAME_RE_
line_num = 1
line_start = 0
pos = 0
limit = len(file_contents)
directive = None
at_bol = True
while pos < limit:
if directive == "include":
mo = HEADER_NAME_RE.match(file_contents, pos)
if mo:
kind = "HEADER_NAME"
directive = "after_include"
else:
mo = PP_TOKEN_RE.match(file_contents, pos)
kind = mo.lastgroup
if kind != "WHITESPACE":
directive = "after_include"
else:
mo = PP_TOKEN_RE.match(file_contents, pos)
kind = mo.lastgroup
text = mo.group()
line = line_num
column = mo.start() - line_start
adj_line_start = 0
# only these kinds can contain a newline
if kind in ("WHITESPACE", "BLOCK_COMMENT", "LINE_COMMENT",
"STRING", "CHARCONST", "BAD_BLOCK_COM", "ESCNL"):
for tmo in ENDLINE_RE.finditer(text):
line_num += 1
adj_line_start = tmo.end()
if adj_line_start:
line_start = mo.start() + adj_line_start
# Track whether or not we are scanning a preprocessing directive.
if kind == "LINE_COMMENT" or (kind == "WHITESPACE" and adj_line_start):
at_bol = True
directive = None
else:
if kind == "PUNCTUATOR" and text == "#" and at_bol:
directive = "<null>"
elif kind == "IDENT" and directive == "<null>":
directive = text
at_bol = False
# Report ill-formed tokens and rewrite them as their well-formed
# equivalents, so downstream processing doesn't have to know about them.
# (Rewriting instead of discarding provides better error recovery.)
if kind == "BAD_BLOCK_COM":
reporter.error(Token("BAD_BLOCK_COM", "", line, column+1, ""),
"unclosed block comment")
text += "*/"
kind = "BLOCK_COMMENT"
elif kind == "BAD_STRING":
reporter.error(Token("BAD_STRING", "", line, column+1, ""),
"unclosed string")
text += "\""
kind = "STRING"
elif kind == "BAD_CHARCONST":
reporter.error(Token("BAD_CHARCONST", "", line, column+1, ""),
"unclosed char constant")
text += "'"
kind = "CHARCONST"
tok = Token(kind, text, line, column+1,
"include" if directive == "after_include" else directive)
# Do not complain about OTHER tokens inside macro definitions.
# $ and @ appear in macros defined by headers intended to be
# included from assembly language, e.g. sysdeps/mips/sys/asm.h.
if kind == "OTHER" and directive != "define":
self.error(tok, "stray {!r} in program")
yield tok
pos = mo.end()
|
