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Draft: Initial support for WebAssembly

Ghost User requested to merge (removed):wasm0 into master

This is initial support for WebAssembly. It generates wasm binaries in the right format, we can execute it in the browser, but there are bugs, see below.

Using this Fortran source as example/Hello WASM

program main
use iso_c_binding

print *, add(1, 1)

integer(kind=c_int) function add(x, y) result(r) bind(c, name="add")
    integer(kind=c_int), intent(in) :: x, y
    r = x + y + 2021
end function

end program

Compile and link

lfortran -c wasm.f90 --target wasm32 -o wasm.o
wasm-ld --no-entry --import-memory wasm.o -o wasm.wasm --export add

Running wasm.wasm in browser. Create an HTML page and add

<script type="module">
// This is from
let imports = {};
let memory = null;
let exports = null;

let request = await fetch('wasm.wasm');
let binary = await request.arrayBuffer();

imports['memory'] = new WebAssembly['Memory']( {'initial':32} );
memory = new Uint8Array( imports['memory']['buffer'] );
let program = await WebAssembly['instantiate']( binary, { "env":imports } );

// BUG: Should print "2030" = (2 + 7 + 2021). It currently prints "2021".
document.getElementById("lfortran").innerHTML = program.instance.exports.add(2, 7);


As you can see, it should print "2030", but it currently prints "2021".


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