[Feature Request] Support 16 KB page sizes

[gustavoabel]

Android 15 introduces support for devices that use a 16 KB page size, and applications that include native libraries must ensure that all ELF segments are aligned to 16 KB boundaries.

The current prebuilt dlib .so files (and even custom builds using the default CMake setup) are still linked with 4 KB alignment.

Sources:

• https://developer.android.com/guide/practices/page-sizes
• https://android.googlesource.com/platform/ndk/+/master/docs/BuildSystemMaintainers.md#Page-sizes
• http://android-developers.googleblog.com/2024/08/adding-16-kb-page-size-to-android.html

[Efe-Sen]

I’m aware that Android 15 requires native libraries to be aligned to 16 KB page boundaries.
I tried adding the following to the CMake configuration:
if(ANDROID)
set_target_properties(dlib PROPERTIES LINK_FLAGS "-Wl,-z,max-page-size=0x4000")
endif()

But even after rebuilding, readelf -l still shows p_align 0x1000 (4 KB).
It looks like the alignment flag isn’t being applied correctly in the current build setup.
Hopefully this will be resolved soon, since Android 15 strictly enforces 16 KB alignment for all native libraries.

[mhsmith]

The current prebuilt dlib .so files (and even custom builds using the default CMake setup) are still linked with 4 KB alignment.

Which prebuilt .so files do you mean?

set_target_properties(dlib PROPERTIES LINK_FLAGS "-Wl,-z,max-page-size=0x4000")

I'm not sure whether the linker accepts hex notation; all the Android links above recommend -Wl,-z,max-page-size=16384.

Also, CMake configuration can be confusing, so I recommend you check the command lines in the build log, and verify that your flags are actually being passed to the linker.

[gustavoabel]

The current prebuilt dlib .so files (and even custom builds using the default CMake setup) are still linked with 4 KB alignment.

Which prebuilt .so files do you mean?

set_target_properties(dlib PROPERTIES LINK_FLAGS "-Wl,-z,max-page-size=0x4000")

I'm not sure whether the linker accepts hex notation; all the Android links above recommend -Wl,-z,max-page-size=16384.

Also, CMake configuration can be confusing, so I recommend you check the command lines in the build log, and verify that your flags are actually being passed to the linker.

@mhsmith There are some, like libdlib.so, libai_core.so, I don't remember them all... do you know if there is a solution?

[mhsmith]

I mean, where did you get this Android build of dlib from? If it's the Chaquopy build from here, that's not an official release of the dlib project.

However, as I mentioned at chaquo/chaquopy#1171 (comment), it may now be possible for them to produce official Android Python wheels using the cibuildwheel tool.

[gustavoabel]

@mhsmith Hey, as I said, I have a mobile app in React Native. We use DLib, it's a facial recognition app, but as I explained, I couldn't find anything in the official DLib repository regarding 16 KB page sizes, so I asked you if you had any solutions.

[mhsmith]

I don't know anything about using dlib in languages other than Python, but the solution will be to recompile dlib with the max-page-size option, as mentioned above.

[davisking]

Yeah there are no official dlib .so files. Users should build dlib themselves with build settings appropriate to their platform. If there is some change to dlib's cmake files that makes things more convenient for some platforms then please put up a PR. But generally speaking, you can do anything you want to build dlib however you want and that's up to users. dlib itself does not dictate how it is built.

[gustavoabel]

Yeah there are no official dlib .so files. Users should build dlib themselves with build settings appropriate to their platform. If there is some change to dlib's cmake files that makes things more convenient for some platforms then please put up a PR. But generally speaking, you can do anything you want to build dlib however you want and that's up to users. dlib itself does not dictate how it is built.

@davisking I use CMake GUI to compile, can you tell me specifically how I compile with support for 16 KB page sizes in it?

[davisking]

Sorry, but I don't know what the right build settings are for your platform. That is, this isn't the right place to ask for how to build C++ code on some platform. Note that dlib is just some C++ code, there isn't anything hardware specific in it. So this is just some build settings that aren't related to dlib.