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import dataclasses as dc
import re
import sys
from typing import NoReturn
from .errors import ParseError
__all__ = ["Monitor"]
TokenAndCondition = tuple[str, str]
TokenStack = list[TokenAndCondition]
def negate(condition: str) -> str:
"""
Returns a CPP conditional that is the opposite of the conditional passed in.
"""
if condition.startswith('!'):
return condition[1:]
return "!" + condition
is_a_simple_defined = re.compile(r'^defined\s*\(\s*[A-Za-z0-9_]+\s*\)$').match
@dc.dataclass(repr=False)
class Monitor:
"""
A simple C preprocessor that scans C source and computes, line by line,
what the current C preprocessor #if state is.
Doesn't handle everything--for example, if you have /* inside a C string,
without a matching */ (also inside a C string), or with a */ inside a C
string but on another line and with preprocessor macros in between...
the parser will get lost.
Anyway this implementation seems to work well enough for the CPython sources.
"""
filename: str
_: dc.KW_ONLY
verbose: bool = False
def __post_init__(self) -> None:
self.stack: TokenStack = []
self.in_comment = False
self.continuation: str | None = None
self.line_number = 0
def __repr__(self) -> str:
parts = (
str(id(self)),
f"line={self.line_number}",
f"condition={self.condition()!r}"
)
return f"<clinic.Monitor {' '.join(parts)}>"
def status(self) -> str:
return str(self.line_number).rjust(4) + ": " + self.condition()
def condition(self) -> str:
"""
Returns the current preprocessor state, as a single #if condition.
"""
return " && ".join(condition for token, condition in self.stack)
def fail(self, msg: str) -> NoReturn:
raise ParseError(msg, filename=self.filename, lineno=self.line_number)
def writeline(self, line: str) -> None:
self.line_number += 1
line = line.strip()
def pop_stack() -> TokenAndCondition:
if not self.stack:
self.fail(f"#{token} without matching #if / #ifdef / #ifndef!")
return self.stack.pop()
if self.continuation:
line = self.continuation + line
self.continuation = None
if not line:
return
if line.endswith('\\'):
self.continuation = line[:-1].rstrip() + " "
return
# we have to ignore preprocessor commands inside comments
#
# we also have to handle this:
# /* start
# ...
# */ /* <-- tricky!
# ...
# */
# and this:
# /* start
# ...
# */ /* also tricky! */
if self.in_comment:
if '*/' in line:
# snip out the comment and continue
#
# GCC allows
# /* comment
# */ #include <stdio.h>
# maybe other compilers too?
_, _, line = line.partition('*/')
self.in_comment = False
while True:
if '/*' in line:
if self.in_comment:
self.fail("Nested block comment!")
before, _, remainder = line.partition('/*')
comment, comment_ends, after = remainder.partition('*/')
if comment_ends:
# snip out the comment
line = before.rstrip() + ' ' + after.lstrip()
continue
# comment continues to eol
self.in_comment = True
line = before.rstrip()
break
# we actually have some // comments
# (but block comments take precedence)
before, line_comment, comment = line.partition('//')
if line_comment:
line = before.rstrip()
if self.in_comment:
return
if not line.startswith('#'):
return
line = line[1:].lstrip()
assert line
fields = line.split()
token = fields[0].lower()
condition = ' '.join(fields[1:]).strip()
if token in {'if', 'ifdef', 'ifndef', 'elif'}:
if not condition:
self.fail(f"Invalid format for #{token} line: no argument!")
if token in {'if', 'elif'}:
if not is_a_simple_defined(condition):
condition = "(" + condition + ")"
if token == 'elif':
previous_token, previous_condition = pop_stack()
self.stack.append((previous_token, negate(previous_condition)))
else:
fields = condition.split()
if len(fields) != 1:
self.fail(f"Invalid format for #{token} line: "
"should be exactly one argument!")
symbol = fields[0]
condition = 'defined(' + symbol + ')'
if token == 'ifndef':
condition = '!' + condition
token = 'if'
self.stack.append((token, condition))
elif token == 'else':
previous_token, previous_condition = pop_stack()
self.stack.append((previous_token, negate(previous_condition)))
elif token == 'endif':
while pop_stack()[0] != 'if':
pass
else:
return
if self.verbose:
print(self.status())
def _main(filenames: list[str] | None = None) -> None:
filenames = filenames or sys.argv[1:]
for filename in filenames:
with open(filename) as f:
cpp = Monitor(filename, verbose=True)
print()
print(filename)
for line in f:
cpp.writeline(line)
if __name__ == '__main__':
_main()
|
