[feature] Add wasm64 arch

[stevenwdv]

What is your suggestion?

Currently, 32-bit wasm (WebAssembly) is supported in settings.yml, but wasm64 is missing. I tried just compiling with -sMEMORY=64 in cflags/cxxflags/exelinkflags/sharedlinkflags, but then got the following error once linking to my own executable:

/home/swdv/emsdk/upstream/emscripten/em++ -sMEMORY64=1 [...] /home/swdv/.conan2/p/b/boosta13dc00a72eaf/p/lib/libboost_iostreams.a [...] :
wasm-ld: error: /home/swdv/.conan2/p/b/boosta13dc00a72eaf/p/lib/libboost_iostreams.a(file_descriptor.o):
    wasm32 object file can't be linked in wasm64 mode

This seems to be caused by the boost recipe, that I use, passing the wrong address-model to b2, apparently causing modules to still be compiled as 32-bit:

Requirements
    boost/1.86.0#ce76e7477e466d7d8cbcf738c5d64175
[...]
boost/1.86.0: WARN: Patching user-config.jam
boost/1.86.0: WARN: 
using "emscripten" :  :  "em++" : 
<cxxflags>"-sMEMORY64=1" <cflags>"-sMEMORY64=1" <linkflags>"-sMEMORY64=1"  ;
boost/1.86.0: Cross building, detecting compiler...
boost/1.86.0: Cross building flags: []
boost/1.86.0: WARN: b2 -q address-model=32 --layout=system --user-config=/home/swdv/.conan2/p/boostcfb011e43f97d/s/src/tools/build/user-config.jam -sNO_ZLIB=1 -sNO_BZIP2=1 -sNO_LZMA=1 -sNO_ZSTD=1 boost.locale.icu=off --disable-icu boost.locale.iconv=off --disable-iconv threading=multi visibility=hidden link=static variant=debug --with-atomic --with-chrono --with-container --with-date_time --with-exception --with-filesystem --with-iostreams --with-log --with-random --with-regex --with-system --with-thread toolset=emscripten cxxstd=2a define=BOOST_DLL_USE_STD_FS=1 pch=on linkflags="" cxxflags="-fPIC" install --prefix=/home/swdv/.conan2/p/b/boost44d6ff027eed3/p -j12 --abbreviate-paths -d0 --debug-configuration --build-dir="/home/swdv/.conan2/p/b/boost44d6ff027eed3/b/build-debug"
boost/1.86.0: RUN: b2 [see above...]
notice: found boost-build.jam at /home/swdv/.conan2/p/boostcfb011e43f97d/s/src/boost-build.jam
notice: loading B2 from /home/swdv/.conan2/p/b20717b8c0763fa/p/bin/.b2/build-system.jam
notice: Searching '/etc' '/home/swdv' '/home/swdv/.conan2/p/b20717b8c0763fa/p/bin/.b2/util' '/home/swdv/.conan2/p/b20717b8c0763fa/p/bin/.b2/tools' '/home/swdv/.conan2/p/b20717b8c0763fa/p/bin/.b2/options' '/home/swdv/.conan2/p/b20717b8c0763fa/p/bin/.b2/contrib' '/home/swdv/.conan2/p/b20717b8c0763fa/p/bin/.b2/build' '/home/swdv/.conan2/p/b20717b8c0763fa/p/bin/.b2' for site-config configuration file 'site-config.jam'.
notice: Configuration file 'site-config.jam' not found in '/etc' '/home/swdv' '/home/swdv/.conan2/p/b20717b8c0763fa/p/bin/.b2/util' '/home/swdv/.conan2/p/b20717b8c0763fa/p/bin/.b2/tools' '/home/swdv/.conan2/p/b20717b8c0763fa/p/bin/.b2/options' '/home/swdv/.conan2/p/b20717b8c0763fa/p/bin/.b2/contrib' '/home/swdv/.conan2/p/b20717b8c0763fa/p/bin/.b2/build' '/home/swdv/.conan2/p/b20717b8c0763fa/p/bin/.b2'.
notice: Loading explicitly specified user configuration file:
    /home/swdv/.conan2/p/boostcfb011e43f97d/s/src/tools/build/user-config.jam
notice: Searching '/home/swdv/.conan2/p/boostcfb011e43f97d/s/src/tools/build' for user-config configuration file 'user-config.jam'.
notice: Loading user-config configuration file 'user-config.jam' from '/home/swdv/.conan2/p/boostcfb011e43f97d/s/src/tools/build'.
notice: will use 'em++' for emscripten, condition <toolset>emscripten-4.0.1
notice: [emscripten-cfg] <toolset>emscripten-4.0.1 :: emcc :: em++
notice: [emscripten-cfg] <toolset>emscripten-4.0.1 :: archiver :: emar
notice: [emscripten-cfg] <toolset>emscripten-4.0.1 :: nodejs version is 22
node: bad option: --experimental-wasm-threads
notice: [emscripten-cfg] <toolset>emscripten-4.0.1 :: nodejs :: node
notice: [openssl] Using pre-installed library
notice: [openssl] Condition
notice: using boost library auto_config <layout>system
notice: iostreams: not using zlib compression 
notice: iostreams: not using bzip compression 
notice: iostreams: not using lzma compression 
notice: iostreams: not using zstd compression 
notice: [python-cfg] Configuring python...
notice: [python-cfg] Checking interpreter command "python"...
notice: [python-cfg] running command 'python -c "from sys import *; print('version=%d.%d\nplatform=%s\nprefix=%s\nexec_prefix=%s\nexecutable=%s' % (version_info[0],version_info[1],platform,prefix,exec_prefix,executable))" 2>&1'
notice: [python-cfg] ...does not invoke a working interpreter
notice: [python-cfg] Python headers and libraries not found.
Performing configuration checks

    - default address-model    : 64-bit [1]
    - default architecture     : none [1]
    - default address-model    : 64-bit [2]
[...]

This is caused by _b2_address_model returning 32 in the boost recipe:

https://github.com/conan-io/conan-center-index/blob/a9b270f9d2052e193ce3c0a6c4e2fda0b0ac5ade/recipes/boost/all/conanfile.py#L1185-L1189

I tried adding boost/*:extra_b2_flags='address-model=64' but it doesn't seem to properly override address-model=32.

Adding wasm64 and updating the boost recipe could solve this. If I can make a suggestion, I also think there should be a centralized function returning the address model, to avoid having to update similar logic in multiple recipes.

I don't know if Conan should also automatically pass -sMEMORY=64 or something.

Setup

Version info

$ conan version
version: 2.11.0
conan_path: /home/swdv/.local/bin/conan
python
  version: 3.10.13
  sys_version: 3.10.13 (main, Sep  5 2023, 06:03:44) [GCC 11.4.0]
  sys_executable: /home/swdv/.local/pipx/venvs/conan/bin/python
  is_frozen: False
  architecture: x86_64
system
  version: #202405300957~1736980680~22.04~44ea8a9 SMP PREEMPT_DYNAMIC Thu J
  platform: Linux-6.9.3-76060903-generic-x86_64-with-glibc2.35
  system: Linux
  release: 6.9.3-76060903-generic
  cpu: x86_64

$ ~/emsdk/emsdk list --uses
The *recommended* precompiled SDK download is 4.0.1 (5ff495a591978fdf8a16f2d172be3616f3150d1e).
[...]

All recent (non-legacy) installable versions are:
         4.0.1    INSTALLED
[...]

The additional following precompiled SDKs are also available for download:
    *    sdk-releases-5ff495a591978fdf8a16f2d172be3616f3150d1e-64bit    INSTALLED
          - node-20.18.0-64bit       
          - releases-5ff495a591978fdf8a16f2d172be3616f3150d1e-64bit
[...]

$ em++ --version
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 4.0.1 (89ce854a99238d04116a3d9b5afe241eec90c6c3)
Copyright (C) 2014 the Emscripten authors (see AUTHORS.txt)
This is free and open source software under the MIT license.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ ~/emsdk/upstream/bin/clang --version
clang version 20.0.0git (https:/github.com/llvm/llvm-project a32e36faf84bd7da3df0c7d50bb9020568128417)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/swdv/emsdk/upstream/bin

Profile

[settings]
arch=wasm
build_type=Debug
compiler=clang
compiler.cppstd=20
compiler.version=19
os=Emscripten

[conf]
tools.build:compiler_executables={'c':'emcc', 'cpp':'em++'}
tools.cmake.cmaketoolchain:user_toolchain=['/home/swdv/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake']
tools.build:cflags=['-sMEMORY64=1']
tools.build:cxxflags=['-sMEMORY64=1']
tools.build:exelinkflags=['-sMEMORY64=1']
tools.build:sharedlinkflags=['-sMEMORY64=1']

[buildenv]
_EMCC_CCACHE=1

Have you read the CONTRIBUTING guide?

• I've read the CONTRIBUTING guide

[memsharded]

Hi @stevenwdv

Thanks for your suggestion.

Improving support for wasm is something that I would like.

Adding wasm64 arch to the default settings could be done very easily, but the value is little, now with settings_user.yml is easy to add new values. The important part is how the different build system integrations and package recipes use that information, and that requires a larger effort and expertise. This is why improvements in wasm haven't been prioritized so far.

If someone wants to help with those, I think the path forward would be something like:

• Start with minimal use cases with mainstream tooling, like a simple CMake library build with wasm, and using the standard integrations such as CMakeToolchain
• Identify there the issues, bottlenecks, etc.
• Fix them with some minimal testing in the codebase
• Move gradually to less mainstream tooling and integration. Likely AutotoolsToolchain, MesonToolchain...
• Then recipes in Conan Center that require custom fixes

[p-groarke]

+1 :)

[stevenwdv]

Btw, for the Boost case, you could look into building Boost with CMake instead of Boost.Build (b2), as vcpkg now does (microsoft/vcpkg#32309).

[perseoGI]

Greetings,

I am pleased to announce that we have introduced native support for wasm64 along with the emcc compiler. These changes are already available in the develop2 branch and are expected to be released in version 2.18 later this week. If you would like to try it out, you can easily do so by cloning the Conan repository and using the development environment.

For more details, please refer to the pull request: #18432.

Additionally, we will soon launch a new repository called conan-toolchains (https://github.com/conan-io/conan-toolchains), where we will be adding and transitioning existing toolchains from CCI. One of these toolchains is emsdk (see conan-io/conan-toolchains#4), which is a refactor of the existing CCI recipe that we plan to deprecate.

We have also implemented proper support for the older asmjs architecture and tested all wasm architectures across different Conan generators, fixing some old bugs.

Please note that in the new conan-toolchains repository, we have added a conan_config folder that can be easily installed using the conan config install command. In this folder, we provide pre-built profiles for the respective toolchains.

Currently, we have the following profiles available:

• emsdk/asmjs
• emsdk/wasm32
• emsdk/wasm64

These profiles can be used alongside emsdk/native, which allows users to utilize their native emsdk installation instead of the Conan-packaged version.

I hope this meets your needs.
Thank you!

[perseoGI]

I'm closing this issue and I appreciate your feedback! If you encounter any issues, please do not hesitate to open a new PR. Happy coding! 🐸