mxsjoberg / pas2wat

Compiler for subset of Pascal targeting WebAssembly text-format

Pascal-to-WebAssembly text-format compiler in Rust

This is an experimental Pascal .pas to WebAssembly text-format .wat compiler written in Rust.

[start here]

Todo

• make SEMICOLON optional (no reason to require in input since omitted in webassembly)
• use func export for procedures (callable within module)
• see data.wat and data.js for implementing string using memory

Usage

Install Rust and Cargo, then:

• cargo test to run unit tests

• cargo run <filename>.pas to run the compiler with <filename>.pas as input, output is <filename>.wat

The generated file is in WebAssembly text-format, test using wat2wasm online tool, or WebAssembly Binary Toolkit:

• build the WebAssembly Binary Toolkit, make wat2wasm executable, and add to PATH, i.e. export PATH=$PATH:/path/to/wat2wasm

• wat2wasm <filename>.wat to compile text-format into binary format, output is <filename>.wasm

• wat2wasm <filename>.wat -v to view the binary format

For example, to compile the file test.pas and view output in binary format:

• cargo run test.pas; wat2wasm test.wat -v

Debug

The compiler can be verbose:

• set DEBUG as true to enter debug mode
• set DEBUG_WITH_INPUT as true to instruct the compiler to look for input file (otherwise expecting call to functions)
• set DEBUG_SHOW_CHAR as true to show characters recognised by the lexer
• set DEBUG_SHOW_CHAR as true to show characters recognised by the lexer
• set DEBUG_SHOW_TOKEN as true to show tokens consumed by the parser
• set DEBUG_SHOW_TREE as true to show the AST representation of the Pascal program, this is the output from parser
• set DEBUG_SHOW_SYMBOL_TABLE as true to show the symbol table, which contains variable decalarations
• set DEBUG_SHOW_ASSIGNMENT_TABLE as true to show the assignment table, which contains variable assignments used by the evaluator

The compiler can generate verbose code:

• set OUTPUT_VERBOSE as true to include compiler-related comments in the generated code, this does not include comments in the Pascal program (default is true)