[Distutils] Why doesn't distutils respect the INCLUDE/LIB environment variable (MSVC)?

[M.-A. Lemburg]

Paul Moore wrote:
> 
> I'm trying to build an extension (Imaging) which depends on a number of external
> libraries (JPEG, Zlib, Tk). Rather than hard code the locations of the libraries
> in the setup.py, I set my INCLUDE and LIB environment variables so that MSVC
> picks up the libraries automatically. Unfortunately, this doesn't seem to work
> properly, as distutils ignores these variables! Checking in the source, I see
> that this is deliberate (see get_msvc_paths and set_path_env_var in
> msvccompiler.py).

I don't see any mention of the reasoning behind not looking
at the OS env vars in sources.
 
> I don't believe that this decision is correct - it leaves the user no way, short
> of modifying the registry manually, to add include/library directories to the
> standard paths. So manually hacking setup.py becomes a necessity.
> 
> Can I suggest that msvccompiler.py *adds* the current entries to INCLUDE and
> LIB, rather than replacing those variables completely. Or at least, that another
> way of including include/library directories external to setup.py be
> available...

Sounds reasonable. 

I don't know about the convention for looking up parameters
on Windows: do env vars override settings in the registry
or the other way around ?

Depending on what the standard procedure is on Windows, I'd
suggest to either prepend or append the env var settings to the 
LIB/INCLUDE values found through the registry.

-- 
Marc-Andre Lemburg
CEO eGenix.com Software GmbH
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