Re: [PATCH 05/10] meson: Add wasm build in build scripts

[Kohei Tokunaga <ktokunaga.mail@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 3666 bytes --]

Hi Paolo, thank you for the comments.

> >> has_int128_type is set to false on emscripten as of now to avoid
errors by
> >> libffi.
>
> What is the error here?  How hard would it be to test for it?

When has_int128_type=true, I encountered a runtime error from libffi. To
reproduce this, we need to actually execute a libffi call with 128-bit
arguments.

> Uncaught TypeError: Cannot convert 1079505232 to a BigInt
>     at ffi_call_js (out.js:702:37)
>     at qemu-system-x86_64.wasm.ffi_call (qemu-system-x86_64.wasm:0xa37712)
>     at qemu-system-x86_64.wasm.tcg_qemu_tb_exec_tci
(qemu-system-x86_64.wasm:0x65f440)
>     at qemu-system-x86_64.wasm.tcg_qemu_tb_exec
(qemu-system-x86_64.wasm:0x65edff)
>     at qemu-system-x86_64.wasm.cpu_tb_exec
(qemu-system-x86_64.wasm:0x6762c0)
>     at qemu-system-x86_64.wasm.cpu_exec_loop
(qemu-system-x86_64.wasm:0x677c84)
>     at qemu-system-x86_64.wasm.dynCall_iii
(qemu-system-x86_64.wasm:0xab9014)
>     at ret.<computed> (out.js:6016:24)
>     at invoke_iii (out.js:7574:10)
>     at qemu-system-x86_64.wasm.cpu_exec_setjmp
(qemu-system-x86_64.wasm:0x676db8)

> >> And tests aren't integrated with Wasm execution environment as of
> >> now so this commit disables tests.
>
> Perhaps it would be enough to add
>
> [binaries]
> exe_wrapper = 'node'
>
> to the emscripten.txt file?

Thank you for the suggestion. I'll explore this approach.

> >> +[built-in options]
> >> +c_args = ['-Wno-unused-command-line-argument','-g','-O3','-pthread']
> >> +cpp_args = ['-Wno-unused-command-line-argument','-g','-O3','-pthread']
> >> +objc_args =
['-Wno-unused-command-line-argument','-g','-O3','-pthread']
> >> +c_link_args = ['-Wno-unused-command-line-argument','-g','-O3','-
> >> pthread','-sASYNCIFY=1','-sPROXY_TO_PTHREAD=1','-sFORCE_FILESYSTEM','-
> >> sALLOW_TABLE_GROWTH','-sTOTAL_MEMORY=2GB','-sWASM_BIGINT','-
> >> sEXPORT_ES6=1','-sASYNCIFY_IMPORTS=ffi_call_js','-
> >> sEXPORTED_RUNTIME_METHODS=addFunction,removeFunction,TTY,FS']
> >> +cpp_link_args = ['-Wno-unused-command-line-argument','-g','-O3','-
> >> pthread','-sASYNCIFY=1','-sPROXY_TO_PTHREAD=1','-sFORCE_FILESYSTEM','-
> >> sALLOW_TABLE_GROWTH','-sTOTAL_MEMORY=2GB','-sWASM_BIGINT','-
> >> sEXPORT_ES6=1','-sASYNCIFY_IMPORTS=ffi_call_js','-
> >> sEXPORTED_RUNTIME_METHODS=addFunction,removeFunction,TTY,FS']
>
> At least -g -O3 -pthread should not be necessary.

Thank you for the suggestion. -sPROXY_TO_PTHREAD flag used in c_link_args
always requires -pthread, even during configuration. Otherwise, emcc returns
an error like:

> emcc: error: -sPROXY_TO_PTHREAD requires -pthread to work!

So I think -pthread needs to be included in c_link_args at minimum. I'll try
to remove other flags in the next version of the series.

> For -Wno-unused-command-line-argument what are the warnings/errors that
> you are getting?

I encountered the following error when compiling QEMU:

> clang: error: argument unused during compilation: '-no-pie'
[-Werror,-Wunused-command-line-argument]

It seems Emscripten doesn't support the -no-pie flag, and this wasn't caught
during the configure phase. It seems that removing
-Wno-unused-command-line-argument would require the following change in
meson.build, but I'm open to better approaches.

> -if not get_option('b_pie')
> +if not get_option('b_pie') and host_os != 'emscripten'
>    qemu_common_flags += cc.get_supported_arguments('-fno-pie', '-no-pie')
>  endif

> >> +elif host_os == 'emscripten'
> >> +  supported_backends += ['fiber']
>
> Can you rename the backend to 'wasm' since the 'windows' backend also
> uses an API called Fibers?

Sure, I'll rename the coroutine backend in the next version of the series.

[-- Attachment #2: Type: text/html, Size: 4732 bytes --]