_socket module cross-compilation error on android-24

[xdegaye]

BPO	28538
Nosy	@doko42, @xdegaye, @moreati
PRs	[Do Not Merge] Convert Misc/NEWS so that it is managed by towncrier #552 bpo-28538: Revert all the changes (now using Android Unified Headers) #4479
Files	if_nameindex.patch

^{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 = <Date 2017-11-23.10:15:27.188>
created_at = <Date 2016-10-26.09:38:53.823>
labels = ['build', '3.7']
title = '_socket module cross-compilation error on android-24'
updated_at = <Date 2017-11-23.10:15:27.187>
user = 'https://github.com/xdegaye'

bugs.python.org fields:

activity = <Date 2017-11-23.10:15:27.187>
actor = 'xdegaye'
assignee = 'none'
closed = True
closed_date = <Date 2017-11-23.10:15:27.188>
closer = 'xdegaye'
components = ['Cross-Build']
creation = <Date 2016-10-26.09:38:53.823>
creator = 'xdegaye'
dependencies = []
files = ['45394']
hgrepos = []
issue_num = 28538
keywords = ['patch']
message_count = 7.0
messages = ['279495', '280340', '283745', '283765', '283768', '306579', '306797']
nosy_count = 4.0
nosy_names = ['doko', 'xdegaye', 'python-dev', 'Alex.Willmer']
pr_nums = ['552', '4479']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue28538'
versions = ['Python 3.6', 'Python 3.7']

[xdegaye]

On the latest Android API level (android-24), the if_nameindex function is now found by configure in Android libc. But the if_nameindex function and structure are still not defined in the Android net/if.h header.

The compilation fails with:

clang --sysroot=/opt/android-ndk/platforms/android-24/arch-x86 -target i686-none-linux-androideabi -gcc-toolchain /opt/android-ndk/toolchains/x86-4.9/prebuilt/linux-x86_64 -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -Wno-unused-value -Wno-empty-body -Qunused-arguments -Wno-parentheses-equality -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -I. -IObjects -IInclude -IPython -I/home/xavier/src/android/pyona/build/python3.7-install-android-24-x86/org.bitbucket.pyona/include -I/opt/android-ndk/platforms/android-24/arch-x86/usr/include -I/path/to/android/cpython/Include -I/home/xavier/src/android/pyona/build/python3.7-android-24-x86 -c /path/to/android/cpython/Modules/socketmodule.c -o build/temp.linux-i686-3.7/path/to/android/cpython/Modules/socketmodule.o
/path/to/android/cpython/Modules/socketmodule.c:1034:29: warning: comparison of integers of different signs: 'socklen_t' (aka 'int') and 'size_t' (aka 'unsigned int') [-Wsign-compare]
        if (res->ai_addrlen < addr_ret_size)
            ~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~
/path/to/android/cpython/Modules/socketmodule.c:1125:25: warning: comparison of integers of different signs: 'socklen_t' (aka 'int') and 'size_t' (aka 'unsigned int') [-Wsign-compare]
    if (res->ai_addrlen < addr_ret_size)
        ~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~
/path/to/android/cpython/Modules/socketmodule.c:4925:15: warning: implicit declaration of function 'sethostname' is invalid in C99 [-Wimplicit-function-declaration]
        res = sethostname(buf.buf, buf.len);
              ^
/path/to/android/cpython/Modules/socketmodule.c:6242:10: warning: implicit declaration of function 'if_nameindex' is invalid in C99 [-Wimplicit-function-declaration]
    ni = if_nameindex();
         ^
/path/to/android/cpython/Modules/socketmodule.c:6242:8: warning: incompatible integer to pointer conversion assigning to 'struct if_nameindex *' from 'int' [-Wint-conversion]
    ni = if_nameindex();
       ^ ~~~~~~~~~~~~~~
/path/to/android/cpython/Modules/socketmodule.c:6250:9: warning: implicit declaration of function 'if_freenameindex' is invalid in C99 [-Wimplicit-function-declaration]
        if_freenameindex(ni);
        ^
/path/to/android/cpython/Modules/socketmodule.c:6254:19: error: subscript of pointer to incomplete type 'struct if_nameindex'
    for (i = 0; ni[i].if_index != 0 && i < INT_MAX; i++) {
                ~~^
/path/to/android/cpython/Modules/socketmodule.c:6240:12: note: forward declaration of 'struct if_nameindex'
    struct if_nameindex *ni;
           ^
/path/to/android/cpython/Modules/socketmodule.c:6256:19: error: subscript of pointer to incomplete type 'struct if_nameindex'
                ni[i].if_index, PyUnicode_DecodeFSDefault, ni[i].if_name);
                ~~^
/path/to/android/cpython/Modules/socketmodule.c:6240:12: note: forward declaration of 'struct if_nameindex'
    struct if_nameindex *ni;
           ^
/path/to/android/cpython/Modules/socketmodule.c:6256:62: error: subscript of pointer to incomplete type 'struct if_nameindex'
                ni[i].if_index, PyUnicode_DecodeFSDefault, ni[i].if_name);
                                                           ~~^
/path/to/android/cpython/Modules/socketmodule.c:6240:12: note: forward declaration of 'struct if_nameindex'
    struct if_nameindex *ni;
           ^
6 warnings and 3 errors generated.

[xdegaye]

Patch attached.

[python-dev]

New changeset e248bfb0f520 by Xavier de Gaye in branch '3.6':
Issue bpo-28538: Fix the compilation error that occurs because if_nameindex() is
https://hg.python.org/cpython/rev/e248bfb0f520

New changeset 55bf0b79ec55 by Xavier de Gaye in branch 'default':
Issue bpo-28538: Merge 3.6.
https://hg.python.org/cpython/rev/55bf0b79ec55

[xdegaye]

These changes break the darwin platform, socket.if_nameindex() is not defined anymore. On Darwin, 'net/if.h' requires that 'sys/socket.h' be included beforehand (see the autoconf documentation).

[python-dev]

New changeset f34dac552ad8 by Xavier de Gaye in branch '3.6':
Issue bpo-28538: On Darwin net/if.h requires that sys/socket.h be included beforehand.
https://hg.python.org/cpython/rev/f34dac552ad8

New changeset c568b6ac5e89 by Xavier de Gaye in branch 'default':
Issue bpo-28538: Merge 3.6.
https://hg.python.org/cpython/rev/c568b6ac5e89

[xdegaye]

These changes are not needed anymore now that Unified Headers are supported by android-ndk-r14 (see bpo-29040)

[xdegaye]

New changeset 5ad7ef8 by xdegaye in branch 'master':
bpo-28538: Revert all the changes (now using Android Unified Headers) (GH-4479)
5ad7ef8