Question

我没有为我的GMainContext正确地减少ref_count。这里的示例程序是一个大型程序的小版本（使用线程，因此需要创建一个上下文并将其推送到线程上）。

GMainLoop *loop;
GMainContext *ctx;

struct conn
{
    GSocketClient *client;

    GSocketConnection *conn;
    GInputStream *in;
    GOutputStream *out;

    gchar data[8192];
    unsigned int count;
};

static void
read_done_cb(GObject *source_object, GAsyncResult *res, gpointer user_data)
{
    struct conn *c = (struct conn *)user_data;
    gssize len = g_input_stream_read_finish(c->in, res, NULL);

    g_input_stream_read_async(c->in, c->data, sizeof c->data / sizeof *c->data, G_PRIORITY_DEFAULT, NULL, read_done_cb, c);
    if (c->count++ == 1) {
        printf("End of life as I know it...\n");
        g_main_loop_quit(loop);
    }
}

static void
write_done_cb(GObject *source_object, GAsyncResult *res, gpointer user_data)
{
}

static void
connect_done_cb(GObject *source_object, GAsyncResult *res, gpointer user_data)
{
    printf("## %s\n", __FUNCTION__);

    struct conn *c = (struct conn *)user_data;
    c->conn = g_socket_client_connect_to_host_finish(c->client, res, NULL);

    c->in  = g_io_stream_get_input_stream(G_IO_STREAM(c->conn));
    c->out = g_io_stream_get_output_stream(G_IO_STREAM(c->conn));

    char *data = "GET /axis-cgi/mjpg/video.cgi HTTP/1.0\r\n\r\n";

    g_output_stream_write_async(c->out, data, strlen(data), G_PRIORITY_DEFAULT, NULL, write_done_cb, c);
    g_input_stream_read_async(c->in, c->data, sizeof c->data / sizeof *c->data, G_PRIORITY_DEFAULT, NULL, read_done_cb, c);
}

int
main(int argc, char **argv)
{
    g_type_init();

    struct conn *c = g_malloc0(sizeof *c);
    ctx = g_main_context_new();
    loop = g_main_loop_new(ctx, FALSE);
    g_main_context_push_thread_default(ctx);

    c->client = g_socket_client_new();
    g_socket_client_connect_to_host_async(c->client, "10.85.25.20", 80, NULL, connect_done_cb, c);

    g_main_loop_run(loop);

    g_io_stream_close(G_IO_STREAM(c->conn), NULL, NULL);
    g_object_unref(c->client);
    g_object_unref(c->conn);
    g_main_context_pop_thread_default(ctx);
    g_main_loop_unref(loop);
    g_main_context_unref(ctx);

    return 0;
}

使用gdb，在返回之前插入断点我可以看到ctx仍有一个引用计数：

(gdb) p ctx->ref_count
 $2 = 1

如果我再做一次g_main_context_unref(ctx);，一切都会按预期关闭。我不明白我在哪里获得这种所有权。

提前感谢您的帮助

Answer 1

我发现了错误。我read_done_cb我在退出主循环后立即发出了另一个g_input_stream_read_async。 g_input_stream_read_async提升了ref_count，但GMainLoop从未有机会返回我的回调（并减少GMainContext上的ref_count）。

将我的回调中的g_input_stream_read_async电话转移到if语句

下方

static void
read_done_cb(GObject *source_object, GAsyncResult *res, gpointer user_data)
{
    struct conn *c = (struct conn *)user_data;
    gssize len = g_input_stream_read_finish(c->in, res, NULL);

    if (c->count++ == 1) {
        printf("End of life as I know it...\n");
        g_main_loop_quit(loop);
    }

    g_input_stream_read_async(c->in, c->data, sizeof c->data / sizeof *c->data, G_PRIORITY_DEFAULT, NULL, read_done_cb, c);

}

正确解析了我主要上下文中的引用次数。

愚蠢的错误。希望有人会至少找到一些我的帖子。

Answer 2

g_main_context_new()，g_main_loop_new()和g_main_context_push_thread_default()都引用了上下文。 g_main_context_pop_thread_default()，g_main_loop_unref()和g_main_context_unref()都不对。所以你的直觉是合理的。

我会在gdb中使用一个观察点：watch ctx->ref_count来找出添加额外引用的位置。

GMainContext有ref_count＆gt;在unf之后0

2 个答案: