Question

What does this two snippet code mean here?

#define HTTPH(a, b, c, d, e, f, g) char b[] =  "*" a ":";  

void function(char *p) {
  (void)p;
}

Answer 1

The first is string concatenation through macro. It is similar to:

#define STR3 STR1 STR2 

With this the preprocessor will concatenate STR1 & STR2 and use it in place of STR3.
Example.

The second syntax:

void function(char *p)
{
  (void)p;
}

Means the pointer variable p is currently unused. Unused variables seldom result in compiler warnings, Such an construct is popularly used to get rid of the unused variable warning.

With (void)p; the pointer p is used in a statement(which in reality does nothing) But it satisfy’s the compiler that the variable was used somewhere and hence it generates no warning.