Variable declarations, using libuv

Question

I am trying to learn how to use libuv. I am on a mac OS X and have the library downloaded and installed. I can compile and run small test programs one only starts a callback

Answer 1

You state that the prototype for the function uv_fs_open is

int uv_fs_open(uv_loop_t* loop, 
               uv_fs_t* req, 
               const char* path, 
               int flags, 
               int mode, 
               uv_fs_cb cb)

Note that the type of the second argument is uv_fs_t*. So when you declare open-rec as

uv_fs_t open_req;

And then call uv_fs_open() with

uv_fs_open(uv_default_loop(), &open_req, argv[1], O_RDONLY, 0, on_open);

the second argument (&open_req) takes the address of open_req and creates the required pointer. This should work just fine. However, from your original error message, I think you did not post all of the relevant code. Let's look at this error message:

invalid conversion from ‘void (*)(uv_fs_t)’ to ‘void (*)(uv_fs_t*)’

This states that the compiler expects a pointer to a function which returns void and takes a single parameter which is a pointer to a uv_fs_t. On the other hand, you are providing a pointer to a function which returns void and takes a single parameter of type uv_fs_t (i.e. not a pointer to uv_fs_t).

This suggests that open_req is a function (or a pointer to a function). In order to help you further, please edit your original question with the declaration of this function as well as how you initialize the open_req variable if it is a pointer to a function rather than the name of the function itself.

Edit:

After a second look at your question, open_req most likely doesn't cause the original error. You should change your code back to the way it was originally.

On the other hand, on_open very likely causes the problem. You declare this function with the prototype

void on_open(uv_fs_t);

but the first line of the definition is

void on_open(uv_fs_t *req)

Remove the * from the first line of the function definition and see what happens.