Compiling for WebAssembly uses host file extensions

[skoppe]

System information

• dub version: (e.g. dub 1.15.0)
• OS Platform and distribution: cross-platform
• compiler version (e.g. ldc2-1.16.0 2.086.1)

Bug Description

Dub isn't aware of the webassembly target and uses host file extensions for static libraries and the final binary. On windows this means the static libraries are named .lib, while ldc expect wasm libraries to have the .a extensions, and the final binary is named .exe. On Linux the final binary has no .wasm extension.

How to reproduce?

• install ldc2 >= 1.15.0
• ensure ldc2 --version shows wasm32 target (I use dlang2/ldc-ubuntu:1.16.0 docker image)
• start empty dub project
• replace app.d with this:

extern(C) void _start() {}

• and dub.sdl with this:

name "wasm-file-extension"
description "A minimal D application."
authors "Sebastiaan Koppe"
copyright "Copyright © 2019, Sebastiaan Koppe"
license "proprietary"
buildRequirements "allowWarnings"
dflags "-mtriple=wasm32-unknown-unknown-wasm" "-betterC" "-fvisibility=hidden"
configuration "library" {
targetType "library"
}
configuration "executable" {
targetType "executable"
}

• and compile with:

dub build --build=release --config=executable
dub build --build=release --config=library

Expected Behavior

On windows the library config should result in an wasm-file-extension.a file. And the executable config should result in a wasm-file-extension.wasm file.

On linux the executable config should result in a wasm-file-extension.wasm file.

[andre2007]

I think there are different ways to solve this. Either by a new build options "wasm" which would be a rather small fix, or by having a complete solution as described here
#228

@wilzbach
Maybe this could be tackled by AOC as part of the multi language support
(https://forum.dlang.org/thread/fhtfxkidkeaetdkquatn@forum.dlang.org).

[skoppe]

I don't know about a new build option, I feel it doesn't fit the bill. I have to look at the code to really propose something, but a new entry for $ARCH seems to be in the right direction. But I don't yet see how dub can infer we are targeting wasm.

[andre2007]

@skoppe please see this pull request regarding the triple for wasm
#1541

[skoppe]

Yeah, I think using triples works great. Do you know if anybody is moving forward on that? I see several issues going back to 2014 about extending arch or using triples.

[andre2007]

There might be a chance that this year someone will work on AOC on "multi language support for Dub" (https://forum.dlang.org/thread/fhtfxkidkeaetdkquatn@forum.dlang.org).
The triple support in general could be a part of that.

But beside of this I am not aware that someone at the moment is active at all on enhancing dub. If there would be a pull by someone ;) the chances are very very high that it is accepted.