8f18ac04d3
Newly supported interpreter definition syntax:
- `op(NAME, (input_stack_effects -- output_stack_effects)) { ... }`
- `macro(NAME) = OP1 + OP2;`
Also some other random improvements:
- Convert `WITH_EXCEPT_START` to use stack effects
- Fix lexer to balk at unrecognized characters, e.g. `@`
- Fix moved output names; support object pointers in cache
- Introduce `error()` method to print errors
- Introduce read_uint16(p) as equivalent to `*p`
Co-authored-by: Brandt Bucher <brandtbucher@gmail.com>
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|---|---|---|
| .. | ||
| generate_cases.py | ||
| lexer.py | ||
| parser.py | ||
| plexer.py | ||
| README.md | ||
Tooling to generate interpreters
What's currently here:
lexer.py: lexer for C, originally written by Mark Shannonplexer.py: OO interface on top of lexer.py; main class:PLexerparser.py: Parser for instruction definition DSL; main classParsergenerate_cases.py: driver script to readPython/bytecodes.cand writePython/generated_cases.c.h
The DSL for the instruction definitions in Python/bytecodes.c is described
here.
Note that there is some dummy C code at the top and bottom of the file
to fool text editors like VS Code into believing this is valid C code.
A bit about the parser
The parser class uses a pretty standard recursive descent scheme,
but with unlimited backtracking.
The PLexer class tokenizes the entire input before parsing starts.
We do not run the C preprocessor.
Each parsing method returns either an AST node (a Node instance)
or None, or raises SyntaxError (showing the error in the C source).
Most parsing methods are decorated with @contextual, which automatically
resets the tokenizer input position when None is returned.
Parsing methods may also raise SyntaxError, which is irrecoverable.
When a parsing method returns None, it is possible that after backtracking
a different parsing method returns a valid AST.
Neither the lexer nor the parsers are complete or fully correct.
Most known issues are tersely indicated by # TODO: comments.
We plan to fix issues as they become relevant.