Fix Android API gating: use weak symbols instead of __ANDROID_API__#229
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The previous API-28 fix (c6bb70d) was a no-op on the current dockcross-android-arm64 image and the Android build still failed compiling mtmd-helper.cpp (vendor/sheredom/subprocess.h -> posix_spawn*). Root cause: that image is NOT the Google NDK CMake toolchain but a Debian-style cross-clang (/usr/aarch64-linux-android/bin/clang). It never sets ANDROID/ANDROID_ABI, so the if(ANDROID_ABI)-guarded add_compile_definitions(__ANDROID_API__=28) never ran; and it ignores -DANDROID_PLATFORM=android-28 (CMake flags it as an unused variable). bionic gates posix_spawn behind __BIONIC_AVAILABILITY_GUARD(28), which tests __ANDROID_MIN_SDK_VERSION__ (predefined by clang from the target triple) — not __ANDROID_API__ — so even applying that define would not have helped. Fix: define __ANDROID_UNAVAILABLE_SYMBOLS_ARE_WEAK__ for the Android build. That forces __BIONIC_AVAILABILITY_GUARD(api) to 1 for every level (declarations always visible) and weak-links symbols newer than the baked-in min-SDK, which resolve at load time on the API-28+ devices the artifact targets. It is never compiler-predefined, so defining it is clean (no -Wmacro-redefined). It also subsumes the getifaddrs (API 24) case. Detection no longer relies on ANDROID_ABI: it uses OS_NAME MATCHES "Android" (CI passes -DOS_NAME=Linux-Android) and the compiler path, plus ANDROID/ANDROID_ABI for a future NDK switch. Also drop the inert -DANDROID_PLATFORM=android-28 from both Android jobs (it only produced an unused-variable warning) and rewrite the CLAUDE.md Android section to document the real mechanism. https://claude.ai/code/session_013jKzHGzz97hiY6t7mp3MGr
bernardladenthin
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Summary
__ANDROID_API__=28approach with__ANDROID_UNAVAILABLE_SYMBOLS_ARE_WEAK__to properly gate Android bionic declarations on the dockcross cross-compiler toolchain-DANDROID_PLATFORM=android-28from CI build commands, as it is ignored by the Debian-style cross-clang used by dockcrossMotivation
The dockcross-android-arm64 image used by CI is not the Google NDK CMake toolchain—it's a Debian-style cross-clang (
/usr/aarch64-linux-android/bin/clang) that:ANDROID/ANDROID_ABICMake variables-DANDROID_PLATFORM(CMake reports it as unused)__ANDROID_API__from its baked-in target tripleThe old approach of bumping
__ANDROID_API__=28doesn't work on this toolchain because it clashes with the compiler's builtin definition and doesn't move__ANDROID_MIN_SDK_VERSION__, which is what bionic's__BIONIC_AVAILABILITY_GUARD(api)actually tests.The working fix is
__ANDROID_UNAVAILABLE_SYMBOLS_ARE_WEAK__, which forces all guarded declarations to be visible and makes newer-API symbols weak references resolved at load time—present on every API-28+ device we target.Changes
CMakeLists.txt:
if(ANDROID_ABI)+add_compile_definitions(__ANDROID_API__=28)with a more robust detection that checksANDROID,ANDROID_ABI,OS_NAME MATCHES "Android", or compiler path__ANDROID_UNAVAILABLE_SYMBOLS_ARE_WEAK__instead of__ANDROID_API__.github/workflows/publish.yml:
-DANDROID_PLATFORM=android-28from bothcrosscompile-android-aarch64andcrosscompile-android-aarch64-opencljob stepsCLAUDE.md:
-DANDROID_PLATFORMin CI-DANDROID_PLATFORM=android-28Test plan
Checklist
CONTRIBUTING.mdandCODE_OF_CONDUCT.mdhttps://claude.ai/code/session_013jKzHGzz97hiY6t7mp3MGr