[SOLVED] WASM import error

[lebao3105]

Hi,

So I am attempting to add WASM to my Github Page. Started with this simple test library:

Code: Pascal  [Select][+][-]

1. library test;
2. uses sysutils;
3.  
4. procedure hello;
5. begin
6.     writeln(Format('hello world from FPC %s for %s', [ {$I %FPCVERSION%}, {$I %FPCTARGETCPU%} ]));
7.     writeln(Format('compiled on %s %s', [ {$I %DATE%}, {$I %TIME%} ]));
8. end;
9.  
10. exports
11.     hello;
12. end.
13.  

Compiled with WASI Preview 1 (target "OS") + WASM32 (target platform) cross-compiler.

The browser instead throws this error: WebAssembly.instantiate(): Import #0 "wasi_snapshot_preview1": module is not an object or function.

The JavaScript part (I think the second parameter is not really correct):

Code: Javascript  [Select][+][-]

1. const res = fetch("test.wasm");
2. await WebAssembly.instantiateStreaming(res, {
3.        test: {
4.              hello: () => {
5.                    console.log("?");
6.              }
7.        },
8. });
9.  

Edit: I know that one can use Pas2JS to create an environment that can be used to load WASM, but is there any other way? Pas2JS returned this error:

C:\fpcupdeluxe\fpcsrc\rtl\win64\windows.pp(19,13) Error: Illegal compiler directive "PackSet"

Its config file is:

Code: Text  [Select][+][-]

1. -vwnh
2. -Sc
3.  
4. -FuC:\fpcupdeluxe\fpcsrc\rtl\win\
5. -FuC:\fpcupdeluxe\fpcsrc\rtl\win64\
6. -FuC:\fpcupdeluxe\fpcsrc\packages\*\src
7. -JiC:\fpcupdeluxe\fpcsrc\utils\pas2js\dist\rtl.js
8.  

Edit 2: Fixed Pas2JS errors. Turns out it uses a separate set of units and RTL.

[Fibonacci]

The browser instead throws this error: WebAssembly.instantiate(): Import #0 "wasi_snapshot_preview1": module is not an object or function.

Your import object is the issue. The second arg to instantiate is what the module wants to *import* from the host - it has nothing to do with exports. hello is an export, so putting it there does nothing. What the module actually imports is wasi_snapshot_preview1, because writeln calls the fd_write syscall and the host must supply it. You provided the wrong module name and omitted the required one, so instantiation fails.

You need a WASI shim JS-side - in the browser, e.g. @bjorn3/browser_wasi_shim. And since a library is a reactor, call wasi.initialize() before calling the export.

Code: Javascript  [Select][+][-]

1. <script type="module">
2. import { WASI, OpenFile, File, ConsoleStdout } from 'https://cdn.jsdelivr.net/npm/@bjorn3/browser_wasi_shim@0.3.0/dist/index.js';
3.  
4. const wasi = new WASI([], [], [
5.   new OpenFile(new File([])),
6.   ConsoleStdout.lineBuffered(console.log),
7.   ConsoleStdout.lineBuffered(console.warn),
8. ]);
9.  
10. const bytes = await (await fetch('test.wasm')).arrayBuffer();
11. const { instance } = await WebAssembly.instantiate(bytes, { wasi_snapshot_preview1: wasi.wasiImport });
12.  
13. wasi.initialize(instance);
14. instance.exports.hello();
15. </script>

FYI: fetch+arrayBuffer instead of instantiateStreaming so it works even when the server doesn't send Content-Type: application/wasm.

[lebao3105]

Your import object is the issue. The second arg to instantiate is what the module wants to *import* from the host - it has nothing to do with exports. hello is an export, so putting it there does nothing. What the module actually imports is wasi_snapshot_preview1, because writeln calls the fd_write syscall and the host must supply it. You provided the wrong module name and omitted the required one, so instantiation fails.

You need a WASI shim JS-side - in the browser, e.g. @bjorn3/browser_wasi_shim. And since a library is a reactor, call wasi.initialize() before calling the export.

Code: Javascript  [Select][+][-]

1. <script type="module">
2. import { WASI, OpenFile, File, ConsoleStdout } from 'https://cdn.jsdelivr.net/npm/@bjorn3/browser_wasi_shim@0.3.0/dist/index.js';
3.  
4. const wasi = new WASI([], [], [
5.   new OpenFile(new File([])),
6.   ConsoleStdout.lineBuffered(console.log),
7.   ConsoleStdout.lineBuffered(console.warn),
8. ]);
9.  
10. const bytes = await (await fetch('test.wasm')).arrayBuffer();
11. const { instance } = await WebAssembly.instantiate(bytes, { wasi_snapshot_preview1: wasi.wasiImport });
12.  
13. wasi.initialize(instance);
14. instance.exports.hello();
15. </script>

FYI: fetch+arrayBuffer instead of instantiateStreaming so it works even when the server doesn't send Content-Type: application/wasm.

Hi, it worked. Almost.

instance.exports does not have hello as exported. But as I fixed Pas2JS, I can consider using it now.

Thanks for helping.

[Fibonacci]

Looks like you're on Windows with fpcupdeluxe (going by your C:\fpcupdeluxe\... paths), so you can just use my wasip1 build script.

Save it as build_wasip1.bat in the folder where FPC is installed - the top-level install folder, next to fpcupdeluxe.ini (for you that's C:\fpcupdeluxe). Run it, wait for it to finish, and from then on you can compile for wasm32 + wasip1. Your library will build fine and actually expose the hello export.

Code: Text  [Select][+][-]

1. @echo off
2. setlocal
3.  
4. rem detect install root (directory where this script lives)
5. set "MYROOT=%~dp0"
6. if "%MYROOT:~-1%"=="\" set "MYROOT=%MYROOT:~0,-1%"
7.  
8. set "MYSRC=%MYROOT%\fpcsrc"
9. set "MYBOOT=%MYROOT%\fpc\bin\x86_64-win64"
10. set "MYDEST=%MYROOT%\fpc"
11.  
12. rem clear env vars that would override GNU make internals
13. set INSTALL=
14. set PREFIX=
15. set FPCDIR=
16.  
17. echo ROOT:        %MYROOT%
18. echo FPCSRC:      %MYSRC%
19. echo BOOTSTRAP:   %MYBOOT%
20. echo INSTALL_DIR: %MYDEST%
21. echo.
22.  
23. if not exist "%MYSRC%\Makefile" (
24.   echo ERROR: Makefile not found in %MYSRC%
25.   exit /b 1
26. )
27. if not exist "%MYBOOT%\make.exe" (
28.   echo ERROR: make.exe not found in %MYBOOT%
29.   exit /b 1
30. )
31. if not exist "%MYBOOT%\ppcx64.exe" (
32.   echo ERROR: ppcx64.exe not found in %MYBOOT%
33.   exit /b 1
34. )
35.  
36. set "PATH=%MYBOOT%;%PATH%"
37.  
38. pushd "%MYSRC%" || exit /b 1
39.  
40. echo [1/3] make clean
41. call make clean CPU_TARGET=wasm32 OS_TARGET=wasip1 || goto :fail
42.  
43. echo [2/3] make all
44. call make all CPU_TARGET=wasm32 OS_TARGET=wasip1 || goto :fail
45.  
46. echo [3/3] make crossinstall
47. call make crossinstall CPU_TARGET=wasm32 OS_TARGET=wasip1 INSTALL_PREFIX=%MYDEST% || goto :fail
48.  
49. popd
50. echo.
51. echo DONE.
52. echo   ppcrosswasm32.exe: %MYDEST%\bin\x86_64-win64
53. echo   units:             %MYDEST%\units\wasm32-wasip1
54. exit /b 0
55.  
56. :fail
57. echo.
58. echo BUILD FAILED at step above.
59. popd
60. exit /b 1

[lebao3105]

Looks like you're on Windows with fpcupdeluxe (going by your C:\fpcupdeluxe\... paths), so you can just use my wasip1 build script.

Save it as build_wasip1.bat in the folder where FPC is installed - the top-level install folder, next to fpcupdeluxe.ini (for you that's C:\fpcupdeluxe). Run it, wait for it to finish, and from then on you can compile for wasm32 + wasip1. Your library will build fine and actually expose the hello export.

Code: Text  [Select][+][-]

1. @echo off
2. setlocal
3.  
4. rem detect install root (directory where this script lives)
5. set "MYROOT=%~dp0"
6. if "%MYROOT:~-1%"=="\" set "MYROOT=%MYROOT:~0,-1%"
7.  
8. set "MYSRC=%MYROOT%\fpcsrc"
9. set "MYBOOT=%MYROOT%\fpc\bin\x86_64-win64"
10. set "MYDEST=%MYROOT%\fpc"
11.  
12. rem clear env vars that would override GNU make internals
13. set INSTALL=
14. set PREFIX=
15. set FPCDIR=
16.  
17. echo ROOT:        %MYROOT%
18. echo FPCSRC:      %MYSRC%
19. echo BOOTSTRAP:   %MYBOOT%
20. echo INSTALL_DIR: %MYDEST%
21. echo.
22.  
23. if not exist "%MYSRC%\Makefile" (
24.   echo ERROR: Makefile not found in %MYSRC%
25.   exit /b 1
26. )
27. if not exist "%MYBOOT%\make.exe" (
28.   echo ERROR: make.exe not found in %MYBOOT%
29.   exit /b 1
30. )
31. if not exist "%MYBOOT%\ppcx64.exe" (
32.   echo ERROR: ppcx64.exe not found in %MYBOOT%
33.   exit /b 1
34. )
35.  
36. set "PATH=%MYBOOT%;%PATH%"
37.  
38. pushd "%MYSRC%" || exit /b 1
39.  
40. echo [1/3] make clean
41. call make clean CPU_TARGET=wasm32 OS_TARGET=wasip1 || goto :fail
42.  
43. echo [2/3] make all
44. call make all CPU_TARGET=wasm32 OS_TARGET=wasip1 || goto :fail
45.  
46. echo [3/3] make crossinstall
47. call make crossinstall CPU_TARGET=wasm32 OS_TARGET=wasip1 INSTALL_PREFIX=%MYDEST% || goto :fail
48.  
49. popd
50. echo.
51. echo DONE.
52. echo   ppcrosswasm32.exe: %MYDEST%\bin\x86_64-win64
53. echo   units:             %MYDEST%\units\wasm32-wasip1
54. exit /b 0
55.  
56. :fail
57. echo.
58. echo BUILD FAILED at step above.
59. popd
60. exit /b 1

I explicitly used wasm+wasip1 before creating this topic.

[Fibonacci]

Well - your code works here, zero modifications: hello is exported and both lines show up in the console. That's why I figured something was off with your wasip1 build.

[lebao3105]

Well - your code works here, zero modifications: hello is exported and both lines show up in the console. That's why I figured something was off with your wasip1 build.

It somehow reappear now? I honestly don't know why, but as all things are resolved by now, I may mark this topic as resolved.

Thank you, once again!