Providing/passing argument to signal handler

You can't have data of your own passed to the signal handler as parameters. Instead you'll have to store your parameters in global variables. (And be really, really careful if you ever need to change those data after installing the the signal handler).

Response to edit 0: Historical reasons. Signals are a really old and really low-level design. Basically you're just given the kernel a single address to some machine code and asking it to go to this specific address if such and such happens. We're back in the "portable assembler" mindset here, where the kernels provide a no-frills baseline service, and whatever the user process can reasonably be expected to to for itself, it must do itself.

Also, the usual arguments against global variables don't really apply here. The signal handler itself is a global setting, so there is no relevant possibility of having several different sets of user-specified parameters for it around. (Well, actually it is not entirely global but only thread-global. But the threading API will include some mechanism for thread-local storage, which is just what you need in this case).

A signal handler registration is already a global state equivalent to global variables. So it's no greater offense to use global variables to pass arguments to it. However, it's a huge mistake (almost certainly undefined behavior unless you're an expert!) to do anything from a signal handler anyway. If you instead just block signals and poll for them from your main program loop, you can avoid all these issues.

This is a really old question but I think I can show you a nice trick that would have answered your problem.No need to use sigqueue or whatever.

I also dislike the use of globals variables so I had to find a clever way, in my case, to send a void ptr (which you can later cast to whatever suits your need).

Actually you can do this :

signal(SIGWHATEVER, (void (*)(int))sighandler); // Yes it works ! Even with -Wall -Wextra -Werror using gcc

Then your sighandler would look like this :

int sighandler(const int signal, void *ptr) // Actually void can be replaced with anything you want , MAGIC !

You might ask : How to get the *ptr then ?

Here's how :At initialization

signal(SIGWHATEVER, (void (*)(int))sighandler)sighandler(FAKE_SIGNAL, your_ptr);

In your sighandler func :

int sighandler(const int signal, void *ptr){  static my_struct saved = NULL;  if (saved == NULL)     saved = ptr;  if (signal == SIGNALWHATEVER)     // DO YOUR STUFF OR FREE YOUR PTR   return (0);}