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May 8, 2009 · Function pointers in C can be used to perform object-oriented programming in C. For example, the following lines is written in C: String s1 = newString(); s1->set(s1, "hello"); Yes, the -> and the lack of a new operator is a dead give away, but it sure seems to imply that we're setting the text of some String class to be "hello".
C-language GUI toolkits and application frameworks (e.g. Gnome/Gtk+/Glib) often accept function pointers as “callbacks” for timer or user interface events. (EG: “call this function whenever this button is clicked” or “…whenever this timer expires”)
Oct 31, 2008 · C distinguishes between object pointers and function pointers (void * is an object pointer), and C does not allow conversion between them. If you turn compiler diagnostics up to -pedantic level you should see warnings.
Oct 20, 2015 · I had seen at some places function pointers declared as . int (*foo) (int a, int b); and at some places a and b are not mentioned and both still works. so . int (*foo) (int, int) is also correct. A very simple way that I found to remember is as mentioned below: Suppose function is declared as: int function (int a , int b);
Apr 5, 2016 · Consider the signal() function from the C standard:. extern void (*signal(int, void(*)(int)))(int); Perfectly obscurely obvious - it's a function that takes two arguments, an integer and a pointer to a function that takes an integer as an argument and returns nothing, and it (signal()) returns a pointer to a function that takes an integer as an argument and returns nothing.
I specifically want to be able have the initializeString() function return a pointer to a PString, and the length function to use a pointer to a PString as input. This is just an experiment in implementing a rudimentary object-oriented system in C, but I don't have a lot of experience dealing with pointers head-on.
Apr 15, 2020 · Initially define a function pointer array which takes a void and returns a void. Assuming that your function is taking a void and returning a void. typedef void (*func_ptr)(void); Now you can use this to create function pointer variables of such functions. Like below: func_ptr array_of_fun_ptr[3];
Mar 8, 2019 · Arrays follow the normal C syntax of putting the brackets near the variable's identifier, so: int (*foo_ptr_array[2])( int ) declares a variable called foo_ptr_array which is an array of 2 function pointers. The syntax can get pretty messy, so it's often easier to make a typedef to the function pointer and then declare an array of those instead:
The "classic" example for the usefulness of function pointers is the C library qsort() function, which implements a Quick Sort. In order to be universal for any and all data structures the user may come up with, it takes a couple of void pointers to sortable data and a pointer to a function that knows how to compare two elements of these data structures.
Mar 4, 2012 · With a function or array, function_name (by itself, not followed by parentheses) doesn't have any other meaning, so there was no problem with interpreting it as taking the address of the function. Likewise in reverse: a normal pointer needs to be dereferenced explicitly, but a pointer to a function doesn't (again, because there's no other reasonable interpretation), so given a pointer to a function like:
