add emscripten-activation

[h-vetinari]

We'll need this to be able to use compiler-jinjas (part of the effort for conda-forge/conda-forge.github.io#2244), and more concretely, I'm running into the lack of compiler activation in conda-forge/zlib-feedstock#84.

The (de)activation scripts are taken almost verbatim from https://github.com/emscripten-forge/recipes/blob/main/recipes/recipes/emscripten_emscripten-wasm32/activate.sh (only removed some BUILD_PREFIX usage).

CC @DerThorsten @wolfv, I added you as maintainers (as in the emscripten-forge recipe already), please let me know if you're (not) OK with that.

[conda-forge-webservices]

Hi! This is the friendly automated conda-forge-linting service.

I wanted to let you know that I linted all conda-recipes in your PR (recipes/emscripten-activation/meta.yaml) and found some lint.

Here's what I've got...

For recipes/emscripten-activation/meta.yaml:

• The following maintainers have not yet confirmed that they are willing to be listed here: wolfv, conda-forge/emscripten, DerThorsten. Please ask them to comment on this PR if they are.

[DerThorsten]

@h-vetinari thanks for pushing this forward. I am fine with being a maintainer

[conda-forge-webservices]

Hi! This is the friendly automated conda-forge-linting service.

I wanted to let you know that I linted all conda-recipes in your PR (recipes/emscripten-activation/meta.yaml) and found some lint.

Here's what I've got...

For recipes/emscripten-activation/meta.yaml:

• The following maintainers have not yet confirmed that they are willing to be listed here: wolfv, conda-forge/emscripten. Please ask them to comment on this PR if they are.

[h-vetinari]

CC @isuruf, I assume you'd like to double-check this. Would appreciate your thoughts.

[wolfv]

Thanks! Happy to be a maintainer :)

[isuruf]

What is the use of this variable?

[h-vetinari]

@DerThorsten, could you comment?

[DerThorsten]

this is very likely some leftover from some debugging in the past, should be removable

[isuruf]

Can you add an example for a shared library building and use?

[h-vetinari]

Fair enough. @DerThorsten, do you have a handy example we could use?

[DerThorsten]

to compile a shared library one needs the -s SIDE_MODULE=1 flag.
For cmake, one needs and additonal

set_property(GLOBAL PROPERTY TARGET_SUPPORTS_SHARED_LIBS TRUE)

without that line above cmake will compile static libraries even when a shared library is demanded.

The -s SIDE_MODULE=1 can be passed like:

set(CMAKE_SHARED_LIBRARY_CREATE_C_FLAGS "-s SIDE_MODULE=1")
set(CMAKE_SHARED_LIBRARY_CREATE_CXX_FLAGS "-s SIDE_MODULE=1")

[h-vetinari]

I think the question was about actually building some concrete example of a shared library as part of the testing for the activation feedstock, rather than just testfile.c.

[DerThorsten]

clapack and geos are build as shared libraries:
https://github.com/emscripten-forge/recipes/tree/main/recipes/recipes_emscripten/clapack
https://github.com/emscripten-forge/recipes/tree/main/recipes/recipes_emscripten/geos

[h-vetinari]

Thanks a lot for the quick review! 🙏

Will clean up the remnants of emscripten-forge, and I think together with @DerThorsten we'll figure out the other points as well.

[conda-forge-webservices]

Hi! This is the friendly automated conda-forge-linting service.

I wanted to let you know that I linted all conda-recipes in your PR (recipes/emscripten-activation/meta.yaml) and found some lint.

Here's what I've got...

For recipes/emscripten-activation/meta.yaml:

• The following maintainers have not yet confirmed that they are willing to be listed here: conda-forge/emscripten. Please ask them to comment on this PR if they are.