ncurses extension uses wrong include path

[chargr]

BPO	36979
Nosy	@yan12125, @websurfer5, @chargr

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-05-20.21:48:43.129>
labels = ['3.7', 'build', 'library']
title = 'ncurses extension uses wrong include path'
updated_at = <Date 2019-05-25.18:55:15.962>
user = 'https://github.com/chargr'

bugs.python.org fields:

activity = <Date 2019-05-25.18:55:15.962>
actor = 'Jeffrey.Kintscher'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Build', 'Library (Lib)']
creation = <Date 2019-05-20.21:48:43.129>
creator = 'chargr'
dependencies = []
files = []
hgrepos = []
issue_num = 36979
keywords = []
message_count = 2.0
messages = ['342957', '343502']
nosy_count = 3.0
nosy_names = ['yan12125', 'Jeffrey.Kintscher', 'chargr']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue36979'
versions = ['Python 3.6', 'Python 3.7']

[chargr]

This is similar to: https://bugs.python.org/issue28190

Not cross-compiling, but using a different ncurses version than is provided under /usr/include/ncursesw

Specifying CPPFLAGS to have "-I/path/to/ncurses/include" does not override the "/usr/include/ncursesw" in setup.py

        if curses_library == 'ncursesw':
            curses_defines.append(('HAVE_NCURSESW', '1'))
            if not cross_compiling:
                curses_includes.append('/usr/include/ncursesw')

Python 2.7.x does not have this issue, but 3.6.x and 3.7.x do. 2 and 3 have different ways of setting up the include path for curses when building the extension.

In my case, removing the curses_include.append from setup.py results in a working extension.

It probably makes sense that Extension(include_dirs=) take priority over Python build CPPFLAGS, setup.py may need to be more cautious about adding the ncurses include path.

Only tested in 2.7, 3.6, 3.7.

[websurfer5]

This explains some of the build/linkage problems encountered in issue bpo-36630, and that I encountered while working on issue bpo-36982.