BLOSC_DIR environment variable seems defunct as of v1.8.3

[mbargull]

The BLOSC_DIR build environment variable does not seem to be used anywhere.
A search on the repository only shows https://github.com/Blosc/python-blosc/search?q=BLOSC_DIR&unscoped_q=BLOSC_DIR :

• https://github.com/Blosc/python-blosc/blob/v1.8.3/doc/install.rst#compiling-with-an-installed-blosc-library
• https://github.com/Blosc/python-blosc/blob/v1.8.3/README.rst#compiling-with-an-installed-blosc-library
• https://github.com/Blosc/python-blosc/blob/v1.8.3/setup.py#L97

The install.rst and README.rst also have to be amended to remove the --blosc=/usr/local option.

[aginiewicz]

Is there some other way to build using system-wide blosc library?

[FrancescAlted]

@aginiewicz that's a good question. I think the BLOSC_DIR support was invalidated after the support for scikit-build compilation method. There was an attempt to support it again, but this was not the correct way for fixing the problem. Maybe @thewtex can suggest a way for fixing this one?

At any rate, this should be either fixed or remove the documentation about it, as @mbargull suggested.

[thewtex]

To best support using a different version of c-blosc in python-blosc and to support using c-blosc in other C/C++ project, a cmake package configuration file should be created by c-blosc, then the path to the directory with this file can be passed with a Blosc_DIR can argument to scikit-build via

python setup.py build -- -DBlosc_DIR=/path/to/c-blosc-build

This enables c-blosc to provide its build configuration and client projects to use it. It is easier to use (everything is provided by the single Blosc_DIR), and it is much more reliable and strongly encouraged over requiring cmake to guess locations and built settings, which is brittle.