BUG: fix packbits and unpackbits to correctly handle empty arrays #8336
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charris
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08 - Backport
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This small PR addresses several problems of numpy.packbits pointed out in Issue #8324.
As discussed in Issue #8324, numpy.packbits have problems with regard to empty input arrays. Specifically:
The fundamental reason for these problems is common: function pack_bits in compiled_base.c handles empty arrays separately, in a rough manner. I could not figure out a good reason why we should handle empty arrays separately. Rather, I found that this part is indeed unnecessary, i.e., without this, pack_bits can handle empty arrays correctly, as confirmed in my new tests. So, I propose to remove that part to fix these problems.