为什么我不能在kitkat的android开源项目中找到_Unwind_Backtrace的实现？

Question

我正在阅读关于在an​​droid的本机代码中执行打印堆栈跟踪的代码，我发现了以下代码：

ssize_t unwind_backtrace(backtrace_frame_t* backtrace, size_t ignore_depth, size_t max_depth) {
    ALOGV("Unwinding current thread %d.", gettid());

    map_info_t* milist = acquire_my_map_info_list();

    backtrace_state_t state;
    state.backtrace = backtrace;
    state.ignore_depth = ignore_depth;
    state.max_depth = max_depth;
    state.ignored_frames = 0;
    state.returned_frames = 0;
    init_memory(&state.memory, milist);

    _Unwind_Reason_Code rc = _Unwind_Backtrace(unwind_backtrace_callback, &state);

    release_my_map_info_list(milist);

    if (state.returned_frames) {
        return state.returned_frames;
    }
    return rc == _URC_END_OF_STACK ? 0 : -1;
}

但是我找不到_Unwind_Backtrace中http://androidxref.com/4.4.2_r2/的实现，有什么机构知道吗？ _Unwind_Backtrace的实施在哪里？

Answer 1

对于android 4.4，unwind_backtrace在/system/core/libcorkscrew/backtrace.c