ffi+drain: route OCaml diagnostics to logcat and trace apply call sites - #20
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I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".
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fprintf(stderr) never reaches logcat on Android (zygote redirects stdio), so the previous exception logging was invisible there — switch to __android_log_print under __ANDROID__. The drain's empty-patch trace showed the create-graph resolution never produced an empty patch and Dart went silent after 'finish id=2' — so applySnapshot either blocked inside the FFI call or hung in the backend apply. Add entry/exit debugPrints around the three drain producers' FFI calls and before/after drain applyPatch, so the next run names the hang.
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Summary
Follow-up to the exception-logging fix — the first diagnostic run showed it can't be observed on Android:
fprintf(stderr)in the FFI writes to/dev/nullon Android (zygote redirects app stdio). Switch to__android_log_printunder__ANDROID__(liblog is already linked bybuild-android-native.sh); stderr fallback stays for iOS/desktop.empty patch from dispatch kind=create-graph(benign) thenfinish id=2 ... coreResponse messageChars=2025— and then silence. Noempty patch from applySnapshot, noresolveEffecttrace, and the create-graph sheet stayed open for the whole timeout.ResolveEffectforCreateGraphEffectis what clearscreate_graph_open, and it runs afterapplySnapshot— soapplySnapshoteither blocked inside the FFI call or the backendapplyPatchhung. AdddebugPrintentry/exit aroundapplySnapshot/resolveEffect/applyHostUpdate(including the busy-queue path) andapplying/appliedtraces aroundapplyPatch— the next logcat will show exactly which call stops returning.Failure evidence (main run 36073266693, maestro
device-logcat.txt): Dart isolate produces zero log lines afterfinish id=2; hierarchy still showslayout.graph-create.sheetopen.Note:
tail -400in the failure logcat dump can miss app lines under Maestro's chatter; thedevice-logcat.txtartifact insideandroid-maestro-debughas the complete buffer.Link to Devin session: https://app.devin.ai/sessions/9a91e201984a4d4f96ce3e0f86ac6668
Open in Devin Desktop: https://app.devin.ai/desktop/session/9a91e201984a4d4f96ce3e0f86ac6668?variant=devin
Requested by: @tiensonqin