Void pointer and casting in function argument

Question

Here is a code snippet.

class NetworkRequestChannel {
public:
  ...

  NetworkRequestChannel(const unsigned short _port_number,
    void * (*connection_handler) (int *));
  ...
private:
  ...
}

My question is about the argument void * (*connection_handler) (int *). I have a vague idea how to read that, and it's as a void pointer to an object named connection_handler that is being then cast to an int pointer. But I know that's almost certainly wrong, and I'm not sure how else to interpret it.

It's a function pointer, accepting a function that takes a single int* as an argument and returns a void* value (a generic memory address). The parameter itself is named connection_handler. — mukunda
– mukunda, Commented May 7, 2016 at 22:55
Note that class NetworkRequestChannel indicates that this is C++, not C. The answer is the same, but the code shown is not valid C. — Jonathan Leffler
– Jonathan Leffler, Commented May 7, 2016 at 22:59
That's something else that I have been confused about for a while. I'll admit, this is for a class, which is why I was trying not to put too many details and just get the one simple answer. However, in all of my professors' assignments, his files are C files with .C and .H extensions. However, HE uses classes even in his own predefined files, and the makefile we are given uses g++ -g. It's like some C/C++ hybrid that he's trying to do that I haven't seen up until this class. — UnworthyToast
– UnworthyToast, Commented May 7, 2016 at 23:01
In my experience, professors aren't really known to use the best practices. :P — mukunda
– mukunda, Commented May 7, 2016 at 23:02
If you do not understand a C declaration try using cdecl.org. — Pixelchemist
– Pixelchemist, Commented May 7, 2016 at 23:14

Christophe · Accepted Answer · 2016-05-07 23:03:14Z

1

The argument

void * (*connection_handler) (int *)

Is a pointer to a function taking one argument of type int* and returning a void*

answered May 7, 2016 at 23:03

Christophe

75.1k7 gold badges87 silver badges182 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

mukunda · Accepted Answer · 2016-05-07 23:08:39Z

0

It's the syntax for a function pointer. The parameter in question accepting a function that takes a single int* as an argument and returns a void* value (a generic memory address).

You can read more about it here.

(That's quite an old article, and I encourage people to comment or edit this answer to list ones that emphasize modern C++ practices. Disregard this if the article I linked is actually up to date with the best practices!)

answered May 7, 2016 at 23:08

mukunda

3,00517 silver badges21 bronze badges

Collectives™ on Stack Overflow

Void pointer and casting in function argument

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related