Build this SDK bundle for Android API 21: dlopen failed

[purpln]

Got libApplication.so building my SwiftPM using --hash-style=both to run on my old android 5.0 device with ndk 21 and failed

dlopen failed: could not load library "libswiftCore.so" needed by "/data/app/<app-id>/lib/arm64/libApplication.so"; caused by empty/missing DT_HASH in "libswiftCore.so" (built with --hash-style=gnu?)

Anyway successfully launched SwiftPM executable using --static-swift-stdlib and linker setting --hash-style=both through adb shell.
(It was only missing stdin, stdout & stderr, that I easily replicated, and missing process_vm_readv & __register_atfork symbols that I defined as empty functions)

Why libraries for android versions 21, 22, 23 are included in your sdk and not supported?

Why do you use minimal version 24 if versions prior it only miss stdin, stdout & stderr?
(They were introduced in 23 and were back ported)
(Also stdout is even not working on android in application mode because logs could be made only through __android_log symbols, so stdin, stdout & stderr are useless)

Is it possible to ask you to use -Wl,--hash-style=both in runtime Swift shared libraries compilation for such crazy-heads like me wanted to use swift on ancient android?

[finagolfin]

Why libraries for android versions 21, 22, 23 are included in your sdk and not supported?

I simply copy over the C/C++ sysroot from the Android NDK, which includes those older C/C++ stub libraries also.

Why do you use minimal version 24 if versions prior it only miss stdin, stdout & stderr?

I wrote this up in my doc years ago:

"This prebuilt SDK was compiled against Android API 24, because the Swift Foundation libraries require some libraries like libcurl, that are pulled from the prebuilt library packages used by the Termux app, which are built against Android API 24. Specifically, it downloads the libandroid-execinfo, libandroid-spawn, libcurl, and libxml2 packages and their handful of dependencies from the Termux package repository."

Is it possible to ask you to use -Wl,--hash-style=both in runtime Swift shared libraries compilation for such crazy-heads like me wanted to use swift on ancient android?

There is work under way on snapshots of an official Android SDK bundle, built against Android API 28, swiftlang/swift#80788. Once that is released this summer, I intend to stop building the 6.2 and trunk 6.3 SDKs in this CI and simply switch over to testing those with some Swift packages.

So no, I'm going the other way and intend to stop distributing SDK bundles here once official release SDK bundles are available. 😄

However, if you want to build for older Android APIs, you can always work on that yourself if you want to. The releases here are completely generated by the CI script and OSS patches in this repo: simply fork this repo, change the Android API to build against to 21 and give it a shot.

Cross-compiling the stdlib will definitely work, as the community Android CI regularly builds the stdlib against API 21, but the corelibs may take some work.

[finagolfin]

Actually, I think I will take a look at this.