Log the native backtrace when exception throws

realm/realm-library/src/main/cpp/CMakeLists.txt

@@ -130,7 +130,7 @@ set(CMAKE_CXX_FLAGS_DEBUG "-ggdb -Og -DNDEBUG")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${REALM_COMMON_CXX_FLAGS} ${WARNING_CXX_FLAGS} ${ABI_CXX_FLAGS}")
 
 # Set link flags
-set(REALM_LINKER_FLAGS "")
+set(REALM_LINKER_FLAGS "-Wl,--wrap=__cxa_throw")
 if (build_SYNC)
     set(REALM_LINKER_FLAGS "${REALM_LINKER_FLAGS} -lz")
 endif()

realm/realm-library/src/main/cpp/jni_util/exception_utils.cpp

@@ -0,0 +1,65 @@
+#include <unwind.h>
+#include <dlfcn.h>
+#include <iomanip>
+#include <android/log.h>
+
+struct BacktraceState
+{
+    void** current;
+    void** end;
+};
+
+static _Unwind_Reason_Code unwindCallback(struct _Unwind_Context* context, void* arg)
+{
+    BacktraceState* state = static_cast<BacktraceState*>(arg);
+    uintptr_t pc = _Unwind_GetIP(context);
+    if (pc) {
+        if (state->current == state->end) {
+            return _URC_END_OF_STACK;
+        } else {
+            *state->current++ = reinterpret_cast<void*>(pc);
+        }
+    }
+    return _URC_NO_REASON;
+}
+
+size_t captureBacktrace(void** buffer, size_t max)
+{
+    BacktraceState state = {buffer, buffer + max};
+    _Unwind_Backtrace(unwindCallback, &state);
+
+    return state.current - buffer;
+}
+
+void dumpBacktrace(std::ostream& os, void** buffer, size_t count)
+{
+    for (size_t idx = 0; idx < count; ++idx) {
+        uintptr_t addr = reinterpret_cast<uintptr_t>(buffer[idx]);
+        uintptr_t base_addr = 0;
+
+        Dl_info info;
+        if (dladdr(reinterpret_cast<void*>(addr), &info)) {
+            base_addr = reinterpret_cast<uintptr_t>(info.dli_fbase);
+        }
+
+        void* real_addr = (void *) (addr - base_addr);
+
+        os << " " << real_addr ;
+    }
+}
+
+extern "C" {
+void __real___cxa_throw(void *ex, void *info, void (*dest)(void *));
+
+void __wrap___cxa_throw(void *ex, void *info, void (*dest)(void *))
+{
+    const size_t max = 30;
+    void* buffer[max];
+    std::ostringstream oss;
+
+    dumpBacktrace(oss, buffer, captureBacktrace(buffer, max));
+
+    __android_log_print(ANDROID_LOG_ERROR, "Backtrace for Native exception: ", "%s", oss.str().c_str());
+    __real___cxa_throw(ex,info,dest);
+}
+}