1

我正在用 libuv 为 C++ 中的流编写一个包装器,但它有段错误,我不知道为什么。流类:

class Stream{
  public:
  Stream(int fd);

  void Write(const std::string& data, const std::function<void(void)>& callback);


  const static int STDIN = 0;
  const static int STDOUT = 1;
  private:
  static void OnWrite(uv_write_t *req, int status);
  uv_pipe_t pipe;
};

以及实施

Stream::Stream(int fd){
  uv_pipe_init(uv_default_loop(), &pipe, 0);
  uv_pipe_open(&pipe, fd);
}

void Stream::Write(const std::string& data, const std::function<void(void)>& callback){
  uv_write_t request;
  uv_buf_t buffer = uv_buf_init((char*)malloc(data.length()*sizeof(char)), data.length());
  strcpy(buffer.base, data.c_str());
  buffer.len = data.length();
  uv_write(&request, (uv_stream_t*)&pipe, &buffer, 1, OnWrite);
}

void Stream::OnWrite(uv_write_t *req, int status){

}

在主文件中,我这样做:

Stream* out = new Stream(Stream::STDOUT);
  out->Write("Hello, World!", []() {
});

uv_run(uv_default_loop(), RUN_DEFAULT);

但是,一旦我运行它,它就会在uv_run语句中出现段错误。回溯:

#0  0x00007ffff7bcac94 in uv__write_callbacks (stream=stream@entry=0x603010) at src/unix/stream.c:907
#1  0x00007ffff7bcb0a1 in uv__stream_io (loop=<optimized out>, w=0x603098, events=<optimized out>) at src/unix/stream.c:1243
#2  0x00007ffff7bc31eb in uv__run_pending (loop=0x7ffff7dd98c0 <default_loop_struct>) at src/unix/core.c:710
#3  uv_run (loop=0x7ffff7dd98c0 <default_loop_struct>, mode=UV_RUN_DEFAULT) at src/unix/core.c:316
#4  0x0000000000400fcd in main ()

但是,如果我将 uv_run 放入Stream::Write方法中,它就可以正常工作。我怎样才能解决这个问题?


编辑

我现在在堆上而不是在堆栈上分配管道,但它仍然给我一个段错误。我uv_pipe_t将标题更改为uv_pipe_t*,现在实现更改为:

Stream::Stream(int fd){
  pipe = new uv_pipe_t;
  uv_pipe_init(uv_default_loop(), pipe, 0);
  uv_pipe_open(pipe, fd);
}

void Stream::Write(const std::string& data, const std::function<void(void)>& callback){
  uv_write_t request;
  uv_buf_t buffer = uv_buf_init((char*)data.c_str(), data.length());
  uv_write(&request, (uv_stream_t*)pipe, &buffer, 1, OnWrite);
}

void Stream::OnWrite(uv_write_t *req, int status){
  delete req;
}

来自 GDB 的回溯:

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7bcac94 in uv__write_callbacks (stream=stream@entry=0x603030) at src/unix/stream.c:907
907         uv__req_unregister(stream->loop, req);
(gdb) backtrace
#0  0x00007ffff7bcac94 in uv__write_callbacks (stream=stream@entry=0x603030) at src/unix/stream.c:907
#1  0x00007ffff7bcb0a1 in uv__stream_io (loop=<optimized out>, w=0x6030b8, events=<optimized out>) at src/unix/stream.c:1243
#2  0x00007ffff7bc31eb in uv__run_pending (loop=0x7ffff7dd98c0 <default_loop_struct>) at src/unix/core.c:710
#3  uv_run (loop=0x7ffff7dd98c0 <default_loop_struct>, mode=UV_RUN_DEFAULT) at src/unix/core.c:316
#4  0x0000000000400f4d in main ()
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1 回答 1

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您的“写请求”(uv_write_t)在堆栈上分配,当 libuv 尝试将其指针传递给写回调函数时(或者,实际上当 libuv 本身尝试使用它时)将不存在。请记住,一切都是异步的库;这可能就是你使用它的原因!

您应该uv_write_t在堆上分配您的(或作为全局/类变量或从池或其他)并记住在写回调中释放它。

您的程序中还有另一个内存/生命周期错误,但这不是崩溃错误,而是产生垃圾的错误。malloc您放入的缓冲区uv_buffer_t不是必需的,可以在调用后立即释放(这是同步的!)实际上,您甚至不需要分配单独的缓冲区;你可以data.c_str()作为第一个参数传递给uv_buf_init().

于 2015-03-28T16:45:52.530 回答