BUG,DEP: Fix writeable flag setting for arrays without base

This also deprecates setting a non-writeable array to writeable if
that array does not own its data (and has no base object to check if
the memory may be writeable). (Deprecation on Python side only)

Closes gh-481

1 files changed, 10 insertions, 0 deletions

diff --git a/doc/release/1.17.0-notes.rst b/doc/release/1.17.0-notes.rst
index 71ad17673..e05709fea 100644
--- a/doc/release/1.17.0-notes.rst
+++ b/doc/release/1.17.0-notes.rst
@@ -33,6 +33,16 @@ The internal use of these functions has been refactored and there are better
 alternatives. Relace ``exec_command`` with `subprocess.Popen` and
 ``temp_file_name`` with `tempfile.mkstemp`.
 
+Writeable flag of C-API wrapped arrays
+--------------------------------------
+When an array is created from the C-API to wrap a pointer to data, the only
+indication we have of the read-write nature of the data is the ``writeable``
+flag set during creation. It is dangerous to force the flag to writeable.
+In the future it will not be possible to switch the writeable flag to ``True``
+from python.
+This deprecation should not affect many users since arrays created in such
+a manner are very rare in practice and only available through the NumPy C-API.
+
 
 Future Changes
 ==============