Issue in nc_def_var_extra with shuffle

[gsjaardema]

This may be related to #1713.

I think there are a few errors in nc_def_var_extra with parallel builds.
I am trying to enable the parallel compression feature, and it is always returning an NC_EINVAL from line 673. This happens whether I have shuffle enabled or not.

#ifndef HDF5_SUPPORTS_PAR_FILTERS
    if (h5->parallel == NC_TRUE)
        if (nclistlength(var->filters) > 0  || fletcher32 || shuffle)
            return NC_EINVAL;
#endif

I think the code is checking shuffle and it should be checking *shuffle (Or, check that shuffle is non-NULL and then check the value and return if the value is non-zero)

Note that the call to this routine from NC4_def_var_deflate is:

    if((stat = nc_def_var_extra(ncid, varid, &shuffle, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL))) goto done;

And shuffle is an integer parameter to NC4_def_var_deflate, so &shuffle will always be a non-NULL address, so the test in nc_def_var_extra

The overall behavior is probably the same since this is inside a block only active if the underlying HDF5 doesn't support parallel compression, so eventually the code will return with NC_EINVAL, but it shouldn't be returning that at this point.

[DennisHeimbigner]

Looks like a correct diagnosis.