From 6a23498962a69238ac142c3151357fb3730bfa9f Mon Sep 17 00:00:00 2001 From: nsfisis Date: Mon, 5 May 2025 07:59:34 +0900 Subject: add readme and license --- README.md | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 58 insertions(+) create mode 100644 README.md (limited to 'README.md') diff --git a/README.md b/README.md new file mode 100644 index 0000000..c2ff956 --- /dev/null +++ b/README.md @@ -0,0 +1,58 @@ +# P4Dcc + +P4Dcc is a tiny, but self-hosted C compiler. It takes C source code and compiles it to assembly language. For assembling and linking, I use gcc as-is. + +This project was started to test the hypothesis: "Could a self-hostable C compiler be built in four days, if the feature set is carefully limited?" - "P4D" stands for the ISO 8601 notation meaning "four days." However, I actually completed the project by the morning of the third day. + +The code is written following the instructions at https://www.sigbus.info/compilerbook, and several key design decisions were inspired by the book. + + +## Dependencies + +* gcc +* [just](https://github.com/casey/just), a general-purpose task runner + + +## Build + +``` +$ just build +``` + + +## Test + +``` +$ just test +$ just test-all # test all things, including binary equiality between generations +``` + + +## Design + +To meet the four-day goal, many design decisions were made to reduce complexity (ideas directly taken from https://www.sigbus.info/compilerbook are not listed): + +* Simplify declaration syntax + * No support for `typedef` + * Structs always begin with `struct` keyword + * No support for array types + * No stack-allocated arrays + * All arrays are heap-allocated and accessed via pointers + * No support for function types + * Type information always precede the variable name +* Most syntax sugar is not implemented + * No increment/decrement operators + * No compound assignment operators + * No `while` +* Limited preprocessor + * Supports only simple `#define` that replaces identifiers with integer literals +* No global variables + * Including `stdin`, `stdout`, and `stderr` + * Only function/struct definitions/declarations are allowed at the top level +* No variable shadowing + * All variables are function-scoped + + +## License + +See [LICENSE](./LICENSE). -- cgit v1.2.3-70-g09d2