Class Monitor

Tools/clinic/libclinic/cpp.py:28–182

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

@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