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Compiling the compiler

Get the sources:

git clone https://github.com/skalogryz/freepascal fpc-wasm

switch to correct branch:

cd fpc-wasm
git checkout webasm


cd compiler

Using Lazarus

 open ppcwasm.lpi

hit the "compile" button.

Using command-line
fpc -dnoopt -dwasm -Fiwasm -Fuwasm -Fusystems -S2 pp.pas 

the compiler can be renamed

mv pp ppwasm

or, on windows:

mv pp.exe ppwasm.exe

Using the compiler

You need a system.pas unit. It can be found here:


You'll also need the wasm tools:

wasm bin tools

Extract the binaries and put them somewhere in your PATH.

And you'll need some more wasm tools:


  • Compile wasmtool.lpi
  • Compile wasmld.lpi and rename wasmld to wasm-ld

Put wasmtool and wasm-ld somewhere in your PATH


Wasm-demo is a Pascal WebAssembly demo project, ported Google's C WebAssembly example (https://codelabs.developers.google.com/codelabs/web-assembly-intro)

You follow these steps in order to get the demo project working:

1. Get the project sources: https://github.com/skalogryz/wasm-demo

Using in webassembly.studio

2. Run the wasm compiler against lyff.pas, but request the assembler file to be kept

 pp -a lyff.pas

Webassembly.studio accepts the assembler file and would compile it on the server side.

3. open up https://webassembly.studio and select "Create empty Wat Project". The project will consist of:


All files of the project can be edited through the web interface.

4. Copy and paste the contents of the following files:

(compiled) lyff.wat to main.wat.
wasm-demo\webassembly.studio\main.html to main.html
wasm-demo\webassembly.studio\main.js to main.js

Note: every time you copy and paste, don't forget to press "SAVE" button (on the right side of the web interface)

5. once all files are update, hit "Build and Run"

See Also