SIGTRAP crash in FPDF_InitLibraryWithConfig on Android during pdfrxFlutterInitialize

[benjaminledet]

Description

Calling pdfrxFlutterInitialize() at app startup causes a fatal SIGTRAP (native signal) on some Android devices. The crash occurs inside FPDF_InitLibraryWithConfig — the PDFium native initialization — before any PDF document is opened.

Since SIGTRAP is a native signal, it kills the entire process and cannot be caught from Dart.

Environment

• pdfrx: 2.2.24
• pdfrx_engine: 0.3.9
• Flutter: 3.41.0 (Dart 3.10.1)
• Platform: Android only (13, 14, 15, 16)

Affected devices (21 occurrences, 19 users)

Device	Chipset	Count
Samsung Galaxy A34 (SM-A346E)	Mediatek MT6877	3
Samsung Galaxy M12 (SM-M127F)	Exynos 850	3
Motorola moto g14	Mediatek	2
Motorola moto g24	Mediatek MT6769	1
Samsung Galaxy A26 (SM-A266B)	—	1
Samsung Galaxy A52s (SM-A528B)	—	1
Realme RMX3933	—	1
Xiaomi Redmi (22101316UG)	—	1
+ others	—	8

Mostly low/mid-range devices with Mediatek or Exynos chipsets. Spans Android 13 through 16, so not version-specific.

Stacktrace

SIGTRAP: Trap
    at __start_thread (<unknown>)
    at __pthread_start (<unknown>)
    at dart::ThreadStart (os_thread_android.cc:98)
    at dart::ThreadPool::Worker::Main (thread_pool.cc:367)
    at dart::ThreadPool::WorkerLoop (thread_pool.cc:207)
    at dart::MessageHandlerTask::Run (message_handler.cc:31)
    at dart::MessageHandler::TaskCallback (message_handler.cc:443)
    at dart::MessageHandler::HandleMessages (message_handler.cc:229)
    at dart::IsolateMessageHandler::HandleMessage (isolate.cc:1561)
    at dart::DartLibraryCalls::HandleMessage (dart_entry.cc:781)
    at dart::DartEntry::InvokeFunction (dart_entry.cc:41)
    at dart::DartEntry::InvokeFunction (dart_entry.cc:171)
    at dart::InvokeDartCode (dart_entry.cc:126)
    at _kDartVmSnapshotInstructions (<unknown>)
    [... unsymbolicated Dart frames ...]
    at _kDartVmSnapshotInstructions (<unknown>)
    at FPDF_InitLibraryWithConfig (<unknown>)
    at <unknown> (<unknown>)

Reproduction

Cannot reliably reproduce — happens on specific device/chipset combinations. Our app calls pdfrxFlutterInitialize() once at startup inside a Sentry wrapper.

[benjaminledet]

Also affects iOS

Same crash on iOS, reported as EXC_BREAKPOINT (the iOS equivalent of SIGTRAP). The stacktrace goes deeper and reveals the crash is inside CPDF_StreamContentParser::InitializeGlobals during FPDF_InitLibraryWithConfig.

10 occurrences, 10 users on iOS.

Stacktrace (iOS)

EXC_BREAKPOINT: Exception 6, Code 1, Subcode 4397573616
    at _pthread_start (<unknown>)
    at InternalFlutterGpu_Texture_AsImage (<unknown>)
    [... Flutter engine frames ...]
    at kDartVmSnapshotInstructions (<unknown>)
    at kDartIsolateSnapshotInstructions (<unknown>)
    [... unsymbolicated Dart frames ...]
    at kDartVmSnapshotInstructions (<unknown>)
    at FPDF_InitLibraryWithConfig (<unknown>)
    at FPDF_InitLibraryWithConfig (<unknown>)
    at CPDF_StreamContentParser::InitializeGlobals (<unknown>)

Affected iOS devices

Device	Count
iPhone 15 (iPhone15,4)	3
iPhone 15 Pro Max (iPhone16,2)	1
iPhone 14 Plus (iPhone14,8)	1
iPhone 16 Pro Max (iPhone17,2)	1
iPhone 14 Pro (iPhone15,2)	1
iPhone 12 Pro (iPhone13,3)	1
+ 2 unknown	2

iOS versions

iOS 18.5, 18.6.2, 26.2.1, 26.3 — spans old and new versions, including high-end devices. Not limited to low-end hardware like the Android side.

[espresso3389]

Do you any other plugin that also uses PDFium? If so, multiple calls to FPDF_InitLibraryWithConfig may get into race condition and results in SIGTRAP.

[espresso3389]

Or, are you using pdfrx on multiple isolates? Because pdfium is single threaded and calling pdfrx on multiple isolates does not improve any performance and sometimes results in such instability.