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BUG: Conversion from ndpointer to array is broken in 1.15 #12421

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eric-wieser opened this issue Nov 19, 2018 · 3 comments
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BUG: Conversion from ndpointer to array is broken in 1.15 #12421

eric-wieser opened this issue Nov 19, 2018 · 3 comments
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00 - Bug 06 - Regression 57 - Close? Issues which may be closable unless discussion continued

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@eric-wieser
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eric-wieser commented Nov 19, 2018 •
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This code:

import ctypes
import numpy as np

arr = (ctypes.c_double * 6)()
nd_ptr_t = np.ctypeslib.ndpointer(dtype=float, shape=(1, 2, 3))
nd_ptr = ctypes.cast(ctypes.pointer(arr), nd_ptr_t)

np.array(nd_ptr)

Gives

#numpy 1.12
array([[[ 0.,  0.,  0.],
        [ 0.,  0.,  0.]]])

# numpy 1.15
ValueError: '<P' is not a valid PEP 3118 buffer format string

#numpy 1.16-dev
ValueError: Unknown PEP 3118 data type specifier 'P'

The above exception was the direct cause of the following exception:

ValueError: '<P' is not a valid PEP 3118 buffer format string

This is problematic, because it breaks ndpointer._check_retval_, which is needed by toinsson/pyrealsense#82. fixed in #12431

This is an example of the problems predicted in #11150

The new spelling is nd_ptr.contents, which is consistent with how ctypes handles other pointer types.
@eric-wieser eric-wieser changed the title BUG: Conversion from ndpointer to array is broken in 1.16 BUG: Conversion from ndpointer to array is broken in 1.15 Nov 19, 2018
@charris charris added this to the 1.16.0 release milestone Nov 20, 2018
@eric-wieser eric-wieser mentioned this issue Nov 21, 2018
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eric-wieser added a commit to eric-wieser/numpy that referenced this issue Nov 21, 2018
@eric-wieser
BUG/ENH: Fix use of ndpointer in return values
73322a0 
This:
* fixes a regression in 1.15, where it became impossible to set the return value of a cdll function to an ndpointer.
* removes ndpointer.__array_interface__, which was being ignored anyway in favor of the PEP3118 buffer protocol
* adds `ndpointer.contents` to recover the lost functionality, while staying in line with the ctypes behavior
* removes another instance of `descr`, which enables overlapping fields to be returned from C functions (such as unions).
* Fixes a long-term bug where using ndpointer as a return type without specifying both type and dtype would produce an object array containing a single `ndpointer`. Now the ndpointer is returned directly.

This relates to numpygh-12421, and likely fixes toinsson/pyrealsense#82
@charris
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charris commented Nov 22, 2018

Should be closed as won't fix? Going to remove the 1.16 milestone.

@charris charris modified the milestones: 1.16.0 release, 1.17.0 release Nov 22, 2018
@eric-wieser
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Probably needs no milestone - can just leave it open in case anyone has the problem and wants to argue here why we ought to fix it

@charris charris removed this from the 1.17.0 release milestone Nov 23, 2018
@mattip mattip mentioned this issue Nov 26, 2018
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@fggp fggp mentioned this issue Feb 17, 2019
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@bsipocz
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bsipocz commented Jun 12, 2022

This was said to be a won't fix 3.5 years ago. How about closing it? (Maybe also adding a won't fix label?)

@bsipocz bsipocz added the 57 - Close? Issues which may be closable unless discussion continued label Jun 12, 2022
@mattip mattip closed this as completed Jun 13, 2022
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