Initial Android Support: alternate

[victorpaleologue]

Hello,
I have been using the branch by @o01eg to build Python for Android (from this PR: #262) and managed to make it work with some extra changes.
I hope this set of changes will be interesting as well.

To avoid requiring to connect to a target device while building (which is hard to achieve on simpler buildfarms), I had to provide certain definitions manually. I tested the build with the following definitions:

"-DBUILD_EXTENSIONS_AS_BUILTIN=ON", // Have the extensions built in the Python library.
"-DANDROID_ALLOW_UNDEFINED_SYMBOLS=ON", // Required because of how Python builds its extensions.

// Remove content or features we do not need.
"-DINSTALL_MANUAL=OFF",
"-DINSTALL_TEST=OFF",
"-DINSTALL_DEVELOPMENT=OFF",
"-DWITH_DOC_STRINGS=OFF",

// Disable some Python extensions that are not supported.
"-DENABLE_CTYPES=OFF",
"-DENABLE_DECIMAL=OFF",
"-DENABLE_GRP=OFF",

// KLUDGE: assuming some properties of the target platform to avoid running
// programs on a target device to deduce them.
"-DX87_DOUBLE_ROUNDING=OFF",
"-DTANH_PRESERVES_ZERO_SIGN=ON",
"-DLOG1P_DROPS_ZERO_SIGN=ON",
"-DPOSIX_SEMAPHORES_NOT_ENABLED=OFF",
"-DHAVE_BROKEN_SEM_GETVALUE=OFF",
"-DHAVE_BROKEN_NICE=OFF",
"-DHAVE_BROKEN_POLL=OFF",
"-DHAVE_WORKING_TZSET=ON",
"-DHAVE_ALIGNED_REQUIRED=ON",
"-DHAVE_BROKEN_MBSTOWCS=OFF",
"-DHAVE_COMPUTED_GOTOS=OFF",
"-DHAVE_GLIBC_MEMMOVE_BUG=OFF",
"-DHAVE_LONG_LONG_FORMAT=OFF",
"-DHAVE_SIZE_T_FORMAT=OFF",

[o01eg]

Nice, I'll try it later, but Fix floating point endianness checks helped to fix them on Github Actions Android emulator. Locally I got:

-- Checking for x64 gcc inline assembler
-- Checking for x64 gcc inline assembler - yes
-- Checking whether C doubles are little-endian IEEE 754 binary64
-- Checking whether C doubles are little-endian IEEE 754 binary64 - yes
-- Checking whether C doubles are big-endian IEEE 754 binary64
-- Checking whether C doubles are big-endian IEEE 754 binary64 - no
-- Checking doubles are ARM mixed-endian IEEE 754 binary64
-- Checking doubles are ARM mixed-endian IEEE 754 binary64 - no
-- Checking whether we can use gcc inline assembler to get and set x87 control word
-- Checking whether we can use gcc inline assembler to get and set x87 control word - yes

But in Github Actions I got:

-- Checking for x64 gcc inline assembler
-- Checking for x64 gcc inline assembler - yes
-- Checking whether C doubles are little-endian IEEE 754 binary64
-- Checking whether C doubles are little-endian IEEE 754 binary64 - yes
-- Checking whether C doubles are big-endian IEEE 754 binary64
-- Checking whether C doubles are big-endian IEEE 754 binary64 - yes
-- Checking doubles are ARM mixed-endian IEEE 754 binary64
-- Checking doubles are ARM mixed-endian IEEE 754 binary64 - yes
-- Checking whether we can use gcc inline assembler to get and set x87 control word
-- Checking whether we can use gcc inline assembler to get and set x87 control word - yes

[jcfr]

@victorpaleologue Thanks for working on the Android support 🙏 and thanks @o01eg for reviewing.

Working on the backlog of pull request, is there anything else from #262 that we should add here ?

[o01eg]

@jcfr I suppose it could be useful to add Github Actions CI build here at least.