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Android 16 / API 36 Adaptation Review

This review is scoped to this repository:

  • tools/ must keep collecting and interpreting memory data on Android 16 devices, including permission-denied fallbacks.
  • demo/memory-lab is a native-code demo APK. This document records the API 36 baseline; current master now targets API 37, so use android_17_adaptation_review.md for current SDK validation.
  • docs/ must explain which conclusions are supported by meminfo, smaps, showmap, hprof, dmabuf, and zram, and which are only hypotheses.

Current Status

Area Status Evidence
Android 16 SDK API 36 baseline retained; current demo SDK is superseded by Android 17 / API 37 demo/memory-lab/app/build.gradle.kts, android_17_adaptation_review.md
AGP/Gradle AGP 9.2.0, Gradle 9.4.1 demo/memory-lab/build.gradle.kts, gradle-wrapper.properties
Edge-to-edge Explicitly enabled with system bar and cutout insets MainActivity.setupSystemBarInsets()
Predictive back No custom back interception, no temporary opt-out required MainActivity
16 KB page size Non-legacy JNI packaging plus 16 KB ELF linker flags app/build.gradle.kts, CMakeLists.txt
Collection fallback proc_meminfo, zram_swap, and dmabuf_debug are included; non-root capture continues tools/live_dumper.py, scripts/capture_memory_lab.sh

Device-side validation is still required on an Android 16 or 16 KB page-size environment.

Build Adaptation

Android 16 maps to API 36. This is the API 36 baseline; current master uses API 37. If validating an API 36 branch, compileSdk and targetSdk must be reviewed separately:

android {
    compileSdk = 36

    defaultConfig {
        targetSdk = 36
    }
}

compileSdk only allows access to API 36. targetSdk opts the app into Android 16 target-only behavior changes.

Before building, verify the local environment:

java -version
ls "$ANDROID_HOME/platforms/android-36"
ls "$ANDROID_HOME/build-tools/36.0.0"

16 KB Page Size

16 KB page size affects both installation/runtime compatibility and memory interpretation:

  • smaps still reports kB values; parsers must not assume 4 KB pages.
  • mmap, ashmem, DirectByteBuffer, and thread stack mappings can show larger page-rounding overhead.
  • Native .so files need 16 KB-compatible ZIP and ELF alignment.
  • Prebuilt SDK .so files must be checked as well.

The demo now uses non-legacy JNI packaging:

packaging {
    jniLibs {
        useLegacyPackaging = false
    }
}

The CMake target also has explicit 16 KB ELF alignment flags:

target_link_options(
        memorylab
        PRIVATE
        "-Wl,-z,max-page-size=16384"
        "-Wl,-z,common-page-size=16384")

Required validation:

cd demo/memory-lab
./gradlew :app:assembleDebug

APK=app/build/outputs/apk/debug/app-debug.apk
"$ANDROID_HOME/build-tools/36.0.0/zipalign" -c -P 16 -v 4 "$APK"

adb install -r "$APK"
adb shell getconf PAGE_SIZE

Pass criteria:

  • zipalign reports verification success.
  • 16 KB test environment returns 16384 from getconf PAGE_SIZE.
  • The native malloc/mmap scenario starts and clears without linker or mmap errors.

Runtime Behavior

For apps targeting API 36, Android 16 disables the edge-to-edge opt-out. The demo now explicitly enters edge-to-edge and applies systemBars | displayCutout insets to its content root.

Predictive back is enabled by default for target 36 apps on Android 16. The demo does not intercept back, so no manifest opt-out is needed. If custom exit/cancel behavior is added later, use supported AndroidX or platform back APIs rather than old key dispatch.

JobScheduler quota changes do not directly affect this Python+ADB collection flow. They can affect the app being analyzed, so Android 16 memory investigations should record foreground/background state, foreground-service state, and standby bucket when background work is part of the scenario.

Collection Matrix

Source Android 16 risk Current strategy
dumpsys meminfo -d ROM output sections can vary Main direction signal, cross-check with HPROF/smaps
gfxinfo Graphics fields vary by ROM/WebView Auxiliary Graphics/GPU signal
smaps User builds often deny access Direct cat -> su -c -> su 0, then degrade
showmap May be permission-limited Best effort
/proc/meminfo Usually readable Always collect system pressure context
zram/swap Kernel fields vary Collect both new and old zRAM fields
dmabuf_debug debugfs usually requires root Best effort, do not treat missing data as zero
HPROF Requires debuggable/internal build or root Demo debug build supports it

Review Checklist

  • API 36 branch or baseline has compileSdk = 36
  • API 36 branch or baseline has targetSdk = 36
  • AGP supports API 36 without suppressing warnings
  • JDK 17 and Build Tools 36 are available
  • APK passes zipalign -c -P 16
  • 16 KB environment reports PAGE_SIZE=16384
  • Edge-to-edge content does not overlap status/nav/cutout areas
  • No legacy back-key dependency
  • Capture includes build fingerprint, Android release/sdk, and page size
  • Non-root capture still produces a useful meminfo/gfxinfo/proc_meminfo/zram report

References