How to use zlib-ng in place of zlib

[Gregory Sjaardema]

The zlib-ng package provides a "next generation" optimized implementation of zlib functionality.  If built with the `+compat` option, then it provides a drop-in replacement for zlib including a `libz.a` and `libz.so` and `zlib.h` with the correct defines/symbols.

I would like to use zlib-ng instead of zlib in a spack build, but am unsure as to how to do this in the best way.

Is there a way to tell spack that whereever `zlib` is needed to instead replace it with `zlib-ng+compat` ?

I don't want to have to go to all packages that have a zlib dependency and add a `zlib-ng` variant, instead it seems like there should be a place where I can specify that zlib-ng provides `libz.so` and then everything proceeds automatically.

Thanks,

..Greg

[Rob Groner]

What you're looking for is in the packages.yaml file.  In there, you can indicate that a certain package provides another package or capability.

packages:

  all:

    providers:

      zlib: [zlib-ng]

Take a look in the docs, I think this is covered there.  It's the way you indicate what packages are providing mpi or blas, etc.