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f40c7887d3
The C tokenizer is useful separately. Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
213 lines
7.7 KiB
Python
213 lines
7.7 KiB
Python
#! /usr/bin/python3
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# Approximation to C preprocessing.
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# Copyright (C) 2019-2022 Free Software Foundation, Inc.
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# This file is part of the GNU C Library.
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#
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# The GNU C Library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# The GNU C Library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with the GNU C Library; if not, see
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# <https://www.gnu.org/licenses/>.
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"""
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Simplified lexical analyzer for C preprocessing tokens.
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Does not implement trigraphs.
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Does not implement backslash-newline in the middle of any lexical
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item other than a string literal.
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Does not implement universal-character-names in identifiers.
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Treats prefixed strings (e.g. L"...") as two tokens (L and "...").
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Accepts non-ASCII characters only within comments and strings.
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"""
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import collections
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import re
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# Caution: The order of the outermost alternation matters.
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# STRING must be before BAD_STRING, CHARCONST before BAD_CHARCONST,
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# BLOCK_COMMENT before BAD_BLOCK_COM before PUNCTUATOR, and OTHER must
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# be last.
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# Caution: There should be no capturing groups other than the named
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# captures in the outermost alternation.
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# For reference, these are all of the C punctuators as of C11:
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# [ ] ( ) { } , ; ? ~
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# ! != * *= / /= ^ ^= = ==
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# # ##
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# % %= %> %: %:%:
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# & &= &&
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# | |= ||
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# + += ++
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# - -= -- ->
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# . ...
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# : :>
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# < <% <: << <<= <=
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# > >= >> >>=
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# The BAD_* tokens are not part of the official definition of pp-tokens;
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# they match unclosed strings, character constants, and block comments,
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# so that the regex engine doesn't have to backtrack all the way to the
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# beginning of a broken construct and then emit dozens of junk tokens.
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PP_TOKEN_RE_ = re.compile(r"""
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(?P<STRING> \"(?:[^\"\\\r\n]|\\(?:[\r\n -~]|\r\n))*\")
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|(?P<BAD_STRING> \"(?:[^\"\\\r\n]|\\[ -~])*)
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|(?P<CHARCONST> \'(?:[^\'\\\r\n]|\\(?:[\r\n -~]|\r\n))*\')
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|(?P<BAD_CHARCONST> \'(?:[^\'\\\r\n]|\\[ -~])*)
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|(?P<BLOCK_COMMENT> /\*(?:\*(?!/)|[^*])*\*/)
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|(?P<BAD_BLOCK_COM> /\*(?:\*(?!/)|[^*])*\*?)
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|(?P<LINE_COMMENT> //[^\r\n]*)
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|(?P<IDENT> [_a-zA-Z][_a-zA-Z0-9]*)
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|(?P<PP_NUMBER> \.?[0-9](?:[0-9a-df-oq-zA-DF-OQ-Z_.]|[eEpP][+-]?)*)
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|(?P<PUNCTUATOR>
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[,;?~(){}\[\]]
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| [!*/^=]=?
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| \#\#?
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| %(?:[=>]|:(?:%:)?)?
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| &[=&]?
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|\|[=|]?
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|\+[=+]?
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| -[=->]?
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|\.(?:\.\.)?
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| :>?
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| <(?:[%:]|<(?:=|<=?)?)?
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| >(?:=|>=?)?)
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|(?P<ESCNL> \\(?:\r|\n|\r\n))
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|(?P<WHITESPACE> [ \t\n\r\v\f]+)
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|(?P<OTHER> .)
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""", re.DOTALL | re.VERBOSE)
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HEADER_NAME_RE_ = re.compile(r"""
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< [^>\r\n]+ >
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| " [^"\r\n]+ "
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""", re.DOTALL | re.VERBOSE)
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ENDLINE_RE_ = re.compile(r"""\r|\n|\r\n""")
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# based on the sample code in the Python re documentation
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Token_ = collections.namedtuple("Token", (
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"kind", "text", "line", "column", "context"))
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Token_.__doc__ = """
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One C preprocessing token, comment, or chunk of whitespace.
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'kind' identifies the token type, which will be one of:
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STRING, CHARCONST, BLOCK_COMMENT, LINE_COMMENT, IDENT,
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PP_NUMBER, PUNCTUATOR, ESCNL, WHITESPACE, HEADER_NAME,
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or OTHER. The BAD_* alternatives in PP_TOKEN_RE_ are
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handled within tokenize_c, below.
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'text' is the sequence of source characters making up the token;
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no decoding whatsoever is performed.
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'line' and 'column' give the position of the first character of the
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token within the source file. They are both 1-based.
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'context' indicates whether or not this token occurred within a
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preprocessing directive; it will be None for running text,
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'<null>' for the leading '#' of a directive line (because '#'
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all by itself on a line is a "null directive"), or the name of
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the directive for tokens within a directive line, starting with
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the IDENT for the name itself.
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"""
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def tokenize_c(file_contents, reporter):
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"""Yield a series of Token objects, one for each preprocessing
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token, comment, or chunk of whitespace within FILE_CONTENTS.
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The REPORTER object is expected to have one method,
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reporter.error(token, message), which will be called to
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indicate a lexical error at the position of TOKEN.
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If MESSAGE contains the four-character sequence '{!r}', that
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is expected to be replaced by repr(token.text).
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"""
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Token = Token_
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PP_TOKEN_RE = PP_TOKEN_RE_
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ENDLINE_RE = ENDLINE_RE_
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HEADER_NAME_RE = HEADER_NAME_RE_
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line_num = 1
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line_start = 0
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pos = 0
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limit = len(file_contents)
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directive = None
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at_bol = True
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while pos < limit:
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if directive == "include":
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mo = HEADER_NAME_RE.match(file_contents, pos)
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if mo:
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kind = "HEADER_NAME"
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directive = "after_include"
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else:
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mo = PP_TOKEN_RE.match(file_contents, pos)
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kind = mo.lastgroup
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if kind != "WHITESPACE":
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directive = "after_include"
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else:
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mo = PP_TOKEN_RE.match(file_contents, pos)
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kind = mo.lastgroup
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text = mo.group()
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line = line_num
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column = mo.start() - line_start
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adj_line_start = 0
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# only these kinds can contain a newline
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if kind in ("WHITESPACE", "BLOCK_COMMENT", "LINE_COMMENT",
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"STRING", "CHARCONST", "BAD_BLOCK_COM", "ESCNL"):
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for tmo in ENDLINE_RE.finditer(text):
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line_num += 1
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adj_line_start = tmo.end()
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if adj_line_start:
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line_start = mo.start() + adj_line_start
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# Track whether or not we are scanning a preprocessing directive.
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if kind == "LINE_COMMENT" or (kind == "WHITESPACE" and adj_line_start):
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at_bol = True
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directive = None
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else:
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if kind == "PUNCTUATOR" and text == "#" and at_bol:
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directive = "<null>"
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elif kind == "IDENT" and directive == "<null>":
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directive = text
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at_bol = False
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# Report ill-formed tokens and rewrite them as their well-formed
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# equivalents, so downstream processing doesn't have to know about them.
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# (Rewriting instead of discarding provides better error recovery.)
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if kind == "BAD_BLOCK_COM":
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reporter.error(Token("BAD_BLOCK_COM", "", line, column+1, ""),
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"unclosed block comment")
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text += "*/"
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kind = "BLOCK_COMMENT"
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elif kind == "BAD_STRING":
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reporter.error(Token("BAD_STRING", "", line, column+1, ""),
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"unclosed string")
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text += "\""
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kind = "STRING"
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elif kind == "BAD_CHARCONST":
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reporter.error(Token("BAD_CHARCONST", "", line, column+1, ""),
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"unclosed char constant")
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text += "'"
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kind = "CHARCONST"
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tok = Token(kind, text, line, column+1,
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"include" if directive == "after_include" else directive)
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# Do not complain about OTHER tokens inside macro definitions.
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# $ and @ appear in macros defined by headers intended to be
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# included from assembly language, e.g. sysdeps/mips/sys/asm.h.
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if kind == "OTHER" and directive != "define":
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self.error(tok, "stray {!r} in program")
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yield tok
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pos = mo.end()
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