Make array_view::operator= non-const

[mdboom]

Here's another C++ pedantry issue.

The operator= in array_view returned a const reference. I think this means that when the compiler needs a non-const reference it is free to use an auto-generated operator=, which of course would be wrong because it doesn't do the reference counting.

This is purely theoretical, of course, since I haven't seen a problem related to this, but I think this change makes things more correct.

[WeatherGod]

Would be funny if this is the underlying reason that agg changed all of
their functions.

That being said, back in my C++ days, I was a heavy user of const&. gcc
would always catch me when I would show even the slightest sign of calling
a non-const method of a const& object. I am doubtful that gcc would
autogenerate a non-const version of the copy constructor, but "explicit is
better than implicit", right?

On Tue, Nov 18, 2014 at 2:41 PM, Michael Droettboom <
notifications@github.com> wrote:

Here's another C++ pedantry issue.

The operator= in array_view returned a const reference. I think this
means that when the compiler needs a non-const reference it is free to use
an auto-generated operator=, which of course would be wrong because it
doesn't do the reference counting.

This is purely theoretical, of course, since I haven't seen a problem

related to this, but I think this change makes things more correct.

You can merge this Pull Request by running

git pull https://github.com/mdboom/matplotlib non-const-operator=

Or view, comment on, or merge it at:

#3813
Commit Summary

• Make array_view::operator= non-const

File Changes

• M src/numpy_cpp.h
  https://github.com/matplotlib/matplotlib/pull/3813/files#diff-0 (2)

Patch Links:

• https://github.com/matplotlib/matplotlib/pull/3813.patch
• https://github.com/matplotlib/matplotlib/pull/3813.diff

—
Reply to this email directly or view it on GitHub
#3813.

[jenshnielsen]

Which compilers do we support? With C++11 you can explicitly delete default constructors https://en.wikipedia.org/wiki/C%2B%2B11#Explicitly_defaulted_and_deleted_special_member_functions
which could be useful in cases like this.

[jenshnielsen]

If nothing else it could be used to debug if the default constructor is initialised.

[ianthomas23]

A C++ compiler will only autogenerate a default assignment operator if one has not been explicitly declared. Hence the existing code is fine. If the assignment operator returns a const reference and a non-const reference is required, the code will not compile.

Having said that, I have no objections to the change.