[Numpy-discussion] Using library-specific headers

[Julian Taylor]

On 09/27/2016 11:09 PM, Pavlyk, Oleksandr wrote:
> Suppose I would like to take advantage of some functions from MKL in
> numpy C source code, which would require to use
>
>
>
> #include “mkl.h”
>
>
>
> Ideally this include line must not break the build of numpy when MKL is
> not present, so my initial approach was to use
>
>
>
> #if defined(SCIPY_MKL_H)
>
> #include “mkl.h”
>
> #endif
>
>
>
> Unfortunately, this did not work when building with gcc on a machine
> where MKL is present on default LD_LIBRARY_PATH, because then the
> distutils code was setting SCIPY_MKL_H preprocessor variable, even
> though mkl headers are not on the C_INCLUDE_PATH.
>
>
>
> What is the preferred solution to include an external library header to
> ensure that code-base continues to build in most common cases?
>
>
>
> One approach I can think of is to set a preprocessor variable, say
> HAVE_MKL_HEADERS in numpy/core/includes/numpy/config.h depending on an
> outcome of building of a simple _configtest.c using
> config.try_compile(), like it is done in numpy/core/setup.py //
>
> / /
>
> Is there a simpler, or a better way?
>

hi,
you could put the header into OPTIONAL_HEADERS in 
numpy/core/setup_common.py. This will define HAVE_HEADERFILENAME_H for 
you but this will not check that the corresponding the library actually 
exists and can be linked.
For that SCIPY_MKL_H is probably the right macro, though its name is 
confusing as it does not check for the header presence ...

Can you tell us more about what from mkl you are attempting to add and 
for what purpos, e.g. is it something that should go into numpy proper 
or just for personal/internal use?

cheers,
Julian