After fixing the libraries sonames on Android in #1907 (to fix koreader/koreader#12348), the dynamic linker on API level 18 (and 19 too I assume) craps out during symbol resolution (cf. comment).

The only way I could get around those type of issues on my meson branch was to bundle (almost) everything into one big library, and this PR does just that.

At first I tried a partial solution, not bundling in native Lua modules, but of course this just resulted in the dynamic loader having another symbol resolution fit when attempting to load common/ssl.so… So you get the full monty, native Lua modules included, no shared objects in assets.7z. The final list of native libraries is:

    71864  1981-01-01 01:01   lib/arm64-v8a/lib7z.so
  1014704  1981-01-01 01:01   lib/arm64-v8a/libc++_shared.so
     4728  1981-01-01 01:01   lib/arm64-v8a/libioctl.so
 18639648  1981-01-01 01:01   lib/arm64-v8a/libkoreader-monolibtic.so
    19584  1981-01-01 01:01   lib/arm64-v8a/libluajit-launcher.so
   689520  1981-01-01 01:01   lib/arm64-v8a/libluajit.so
  1908280  1981-01-01 01:01   lib/arm64-v8a/libsdcv.so

For now, monolibtic mode is only enabled for Android (but I tested the emulator and kindlepw2 builds too).

On Android, there's no need for the sdcv and libs symlinks in the application files directory anymore: both executable and libraries are directly loaded from the application native libraries directory (fixing this corner case).

Implementation

• build a bunch of static libraries
• link everything, taking advantage of utils/gen_linker_exports.sh and our FFI cdecls to only keep what we need
• use ffi.loadlib(…) instead of ffi.load to load our libraries (and a custom package loader to handle bundled native Lua modules)
• required changes in main project: koreader/koreader@master...benoit-pierre:koreader:4921e1f
• required changes in android-luajit-launcher: koreader/android-luajit-launcher@master...benoit-pierre:android-luajit-launcher:monolibtic

ffi.loadlib module

Apart from a host of commits to facilitate bundling everything, another big change is the ffi.loadlib helper, replacing ffi.load and util.ffiLoadCandidates for loading our libraries.

Example use:

function util.loadSDL2()
    if libSDL2 == nil then
        local ok
        ok, libSDL2 = pcall(ffi.loadlib,
            "SDL2-2.0", 0,
            "SDL2-2.0", nil,
            "SDL2", nil
        )
        if not ok then
            print("SDL2 not loaded:", libSDL2)
            libSDL2 = false
        end
    end
    return libSDL2 or nil
end

On Linux, the code will attempt to load libSDL2-2.0.so.0 in libs/ and then from the system, then libSDL2-2.0.so if that failed, and fallback to trying libSDL2.so.

In monolibtic mode, loading a bundled library will ffi.load the monolibtic library. A custom package loader handle the require("libs/libkoreader-lfs") case.

Code size

Impact on code size (bss+data+text, ignoring executables and the cURL library):

Impact on memory use: a slight increase at startup (starting with the FM, +0-2 MB), but a reduction after opening a few documents of different types (-2-8 MB).

TODO

If the solution is accepted, split the change into smaller PRs for merging: preliminary cleanups, ffi.loadlib module / helper, FFI cdecls cleanups, cURL static build, other static libraries support, final monolitic commit.

This change is