正确关闭 libUV 处理

Question

我正在尝试找出如何修复使用 Valgrind 运行此程序时遇到的这些内存泄漏。泄漏发生在

nShell_client_main

中的两个分配中。但我不是确定如何正确释放它们。

我尝试在 nShell_Connect 处释放它们，但这会导致 libUV 中止程序。我尝试在

nShell_client_main

结束时释放它们，但是在关闭循环时出现读/写错误。有谁知道我应该如何关闭这些句柄？我读过this，这让我开始了。但是，它似乎已经过时了，因为

uv_ip4_addr

在最新版本中有不同的原型。

（

nShell_main

是“入口”点）

#include "nPort.h"
#include "nShell-main.h"

void nShell_Close(
    uv_handle_t * term_handle
){
}

void nShell_Connect(uv_connect_t * term_handle, int status){
    uv_close((uv_handle_t *) term_handle, 0);
}

nError * nShell_client_main(nShell * n_shell, uv_loop_t * n_shell_loop){

    int uv_error = 0;

    nError * n_error = 0;

    uv_tcp_t * n_shell_socket = 0;
    uv_connect_t * n_shell_connect = 0;

    struct sockaddr_in dest_addr;

    n_shell_socket = malloc(sizeof(uv_tcp_t));

    if (!n_shell_socket){
        // handle error
    }

    uv_error = uv_tcp_init(n_shell_loop, n_shell_socket);

    if (uv_error){
        // handle error
    }

    uv_error = uv_ip4_addr("127.0.0.1", NPORT, &dest_addr);

    if (uv_error){
        // handle error
    }

    n_shell_connect = malloc(sizeof(uv_connect_t));

    if (!n_shell_connect){
        // handle error
    }

    uv_error = uv_tcp_connect(n_shell_connect, n_shell_socket, (struct sockaddr *) &dest_addr, nShell_Connect);

    if (uv_error){
        // handle error
    }

    uv_error = uv_run(n_shell_loop, UV_RUN_DEFAULT);

    if (uv_error){
        // handle error
    }

    return 0;
}

nError * nShell_loop_main(nShell * n_shell){

    int uv_error = 0;

    nError * n_error = 0;

    uv_loop_t * n_shell_loop = 0;

    n_shell_loop = malloc(sizeof(uv_loop_t));

    if (!n_shell_loop){
        // handle error
    }

    uv_error = uv_loop_init(n_shell_loop);

    if (uv_error){
        // handle error
    }

    n_error = nShell_client_main(n_shell, n_shell_loop);

    if (n_error){
        // handle error
    }

    uv_loop_close(n_shell_loop);
    free(n_shell_loop);

    return 0;
}

断言发生在这段代码摘录中的 switch 语句末尾（取自 Github 上的 Joyent 的 libUV 页面）：

void uv_close(uv_handle_t* handle, uv_close_cb close_cb) {
  assert(!(handle->flags & (UV_CLOSING | UV_CLOSED)));

  handle->flags |= UV_CLOSING;
  handle->close_cb = close_cb;

  switch (handle->type) {
  case UV_NAMED_PIPE:
    uv__pipe_close((uv_pipe_t*)handle);
    break;

  case UV_TTY:
    uv__stream_close((uv_stream_t*)handle);
    break;

  case UV_TCP:
    uv__tcp_close((uv_tcp_t*)handle);
    break;

  case UV_UDP:
    uv__udp_close((uv_udp_t*)handle);
    break;

  case UV_PREPARE:
    uv__prepare_close((uv_prepare_t*)handle);
    break;

  case UV_CHECK:
    uv__check_close((uv_check_t*)handle);
    break;

  case UV_IDLE:
    uv__idle_close((uv_idle_t*)handle);
    break;

  case UV_ASYNC:
    uv__async_close((uv_async_t*)handle);
    break;

  case UV_TIMER:
    uv__timer_close((uv_timer_t*)handle);
    break;

  case UV_PROCESS:
    uv__process_close((uv_process_t*)handle);
    break;

  case UV_FS_EVENT:
    uv__fs_event_close((uv_fs_event_t*)handle);
    break;

  case UV_POLL:
    uv__poll_close((uv_poll_t*)handle);
    break;

  case UV_FS_POLL:
    uv__fs_poll_close((uv_fs_poll_t*)handle);
    break;

  case UV_SIGNAL:
    uv__signal_close((uv_signal_t*) handle);
    /* Signal handles may not be closed immediately. The signal code will */
    /* itself close uv__make_close_pending whenever appropriate. */
    return;

  default:
    assert(0); // assertion is happening here
  }

  uv__make_close_pending(handle);
}

我可以手动调用

uv__tcp_close

，但它不在公共标头中（而且可能不是正确的解决方案）。

Answer 1

libuv 在调用其关闭回调之前不会处理完句柄。这正是您可以释放手柄的时刻。

我看到你调用了

uv_loop_close

，但你没有检查返回值。如果仍有待处理的句柄，它将返回 UV_EBUSY，因此您应该检查这一点。

如果要关闭循环并关闭所有句柄，则需要执行以下操作：

使用
```
uv_stop
```
停止循环
使用
```
uv_walk
```
并在所有未关闭的句柄上调用
```
uv_close
```
使用
```
uv_run
```
再次运行循环，以便调用所有关闭回调，并且您可以释放回调中的内存
调用
```
uv_loop_close
```
，现在应该返回0

Answer 2

我终于弄清楚如何停止循环并清理所有句柄。我创建了一堆句柄和 SIGINT 信号句柄：

uv_signal_t *sigint = new uv_signal_t;
uv_signal_init(uv_default_loop(), sigint);
uv_signal_start(sigint, on_sigint_received, SIGINT);

当收到 SIGINT 时（在控制台中按下 Ctrl+C），将调用

on_sigint_received

回调。

on_sigint_received

看起来像：

void on_sigint_received(uv_signal_t *handle, int signum)
{
    int result = uv_loop_close(handle->loop);
    if (result == UV_EBUSY)
    {
        uv_walk(handle->loop, on_uv_walk, NULL);
    }
}

触发回调函数

on_uv_walk

:

void on_uv_walk(uv_handle_t* handle, void* arg)
{
    uv_close(handle, on_uv_close);
}

它尝试关闭每个打开的 libuv 句柄。 注意：我不会在

uv_stop

之前调用

uv_walk

，正如提到的saghul。调用

on_sigint_received

函数后，libuv 循环继续执行，并在下一次迭代中为每个打开的句柄调用

on_uv_close

。如果调用

uv_stop

函数，则不会调用

on_uv_close

回调。

void on_uv_close(uv_handle_t* handle)
{
    if (handle != NULL)
    {
        delete handle;
    }
}

之后 libuv 没有打开的句柄并完成循环（从

uv_run

退出）：

uv_run(uv_default_loop(), UV_RUN_DEFAULT);
int result = uv_loop_close(uv_default_loop());
if (result)
{
    cerr << "failed to close libuv loop: " << uv_err_name(result) << endl;
}
else
{
    cout << "libuv loop is closed successfully!\n";
}

Answer 3

我喜欢Konstantin Gindemit

给出的解决方案

但是我确实遇到了一些问题。他的 on_uv_close() 函数以核心转储结束。此外 uv_signal_t 变量导致 valgrind 报告“肯定丢失”内存泄漏。

我正在使用他的代码来修复这两种情况。

void on_uv_walk(uv_handle_t* handle, void* arg) {
    uv_close(handle, NULL);
}

void on_sigint_received(uv_signal_t *handle, int signum) {
    int result = uv_loop_close(handle->loop);
    if(result == UV_EBUSY) {
        uv_walk(handle->loop, on_uv_walk, NULL);
    }
}

int main(int argc, char *argv[]) {
    uv_signal_t *sigint = new uv_signal_t;
    uv_signal_init(uv_default_loop(), sigint);
    uv_signal_start(sigint, on_sigint_received, SIGINT);
    uv_loop_t* main_loop = uv_default_loop();
...
    uv_run(main_loop, UV_RUN_DEFAULT));
    uv_loop_close(uv_default_loop());
    delete sigint;
    return 0;
}

Answer 4

我认为这与Jeff Greer的答案基本相同，但有更多背景。

与让 valgrind 使用最新版本的 libuv 相关，我发现某些行受到

libuv/test/task.h

的祝福，使得 2 个误报释放消失了。

// You have to define this. DON'T define this to assert as it will skip the call when NDEBUG is defined
#define ASSERT(expr) expr

// Secret knowledge hidden within libuv's test folder
static void close_walk_cb(uv_handle_t* handle, void* arg) {
  if (!uv_is_closing(handle))
    uv_close(handle, NULL);
}

static void close_loop(uv_loop_t* loop) {
  uv_walk(loop, close_walk_cb, NULL);
  uv_run(loop, UV_RUN_DEFAULT);
}

/* This macro cleans up the event loop. This is used to avoid valgrind
 * warnings about memory being "leaked" by the event loop.
 */
#define MAKE_VALGRIND_HAPPY(loop)                   \
  do {                                              \
    close_loop(loop);                               \
    ASSERT(0 == uv_loop_close(loop));               \
    uv_library_shutdown();                          \
  } while (0)

你就这样用吧

// Signal handling stuff for ctrl+C 
// This one is needed if you something set on server->data needs to be freed
void on_close(uv_handle_t* handle) {
    // free(handle->data); <- Uncomment if you know you need to free this
}

// Actual signal handler
void on_signal(uv_signal_t *handle, int signum) {
    uv_tcp_t *server = handle->data;
    uv_close((uv_handle_t*) server, on_close);
    uv_stop(handle->loop);
}

int main() {
    uv_tcp_t server;
    uv_tcp_init(uv_default_loop(), &server);

    struct sockaddr_in addr;
    uv_ip4_addr("0.0.0.0", DEFAULT_PORT, &addr);

    uv_tcp_bind(&server, (const struct sockaddr*)&addr, 0);
    int r = uv_listen((uv_stream_t*) &server, DEFAULT_BACKLOG, on_new_connection);

    // Don't forget this step if you're closing the program with ctrl+C
    uv_signal_t sig;
    uv_signal_init(loop, &sig);
    sig.data = &server;
    uv_signal_start(&sig, on_signal, SIGINT);

    uv_run(loop, UV_RUN_DEFAULT);

    uv_loop_close(loop);

    MAKE_VALGRIND_HAPPY(uv_default_loop());
}

在没有请求的情况下使用 ctrl-c 启动和关闭服务器时 valgrind 的输出

MAKE_VALGRIND_HAPPY

被注释掉了

make; valgrind --leak-check=full --show-leak-kinds=all --errors-for-leak-kinds=all --error-exitcode=1 --exit-on-first-error=yes ./server
make: `server' is up to date.
==9426== Memcheck, a memory error detector
==9426== Copyright (C) 2002-2022, and GNU GPL'd, by Julian Seward et al.
==9426== Using Valgrind-3.19.0 and LibVEX; rerun with -h for copyright info
==9426== Command: ./server
==9426== 
^Csig.c:410: Closing
==9426== 
==9426== HEAP SUMMARY:
==9426==     in use at exit: 200 bytes in 2 blocks
==9426==   total heap usage: 4 allocs, 2 frees, 1,256 bytes allocated
==9426== 
==9426== 72 bytes in 1 blocks are still reachable in loss record 1 of 2
==9426==    at 0x54AE1F4: calloc (vg_replace_malloc.c:1328)
==9426==    by 0x54EDD6F: uv_loop_init (in /usr/lib64/libuv.so.1.0.0)
==9426==    by 0x54E64A7: uv_default_loop (in /usr/lib64/libuv.so.1.0.0)
==9426==    by 0x401B3F: main (sig.c:445)
==9426== 
==9426== 
==9426== Exit program on first error (--exit-on-first-error=yes)

刚刚使用 ctrl-c 启动和关闭服务器时 valgrind 的输出，没有请求

MAKE_VALGRIND_HAPPY

在

main

结束时执行

make; valgrind --leak-check=full --show-leak-kinds=all --errors-for-leak-kinds=all --error-exitcode=1 --exit-on-first-error=yes ./server
clang -o server -Wall -Wsizeof-pointer-div -Wmissing-field-initializers -O0 -g3 sig.c -luv
==9542== Memcheck, a memory error detector
==9542== Copyright (C) 2002-2022, and GNU GPL'd, by Julian Seward et al.
==9542== Using Valgrind-3.19.0 and LibVEX; rerun with -h for copyright info
==9542== Command: ./server
==9542== 
^Csig.c:410: Closing
==9542== 
==9542== HEAP SUMMARY:
==9542==     in use at exit: 0 bytes in 0 blocks
==9542==   total heap usage: 4 allocs, 4 frees, 1,256 bytes allocated
==9542== 
==9542== All heap blocks were freed -- no leaks are possible
==9542== 
==9542== For lists of detected and suppressed errors, rerun with: -s
==9542== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

正确关闭 libUV 处理

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最新问题

正确关闭 libUV 处理

问题描述 投票：0回答：4

4个回答

最新问题

问题描述投票：0回答：4