In the previous tutorial we learned how to create functions that will accept pointers as argument. In this tutorial we will learn to return pointer from function in c programming language. This post will going into c function pointers from the basics to simple usage to some quirks about function names and addresses. So return type of function can be pointer to structre, pointer to union and pointer to enum. To do so, you would have to declare a function returning a pointer as in the following example int myfunction. For example, the type of a function accepting two int and returning an int is. Function returning pointer to derived data type in c derived data types are.
Thus all functions, you want to use with the same function pointer, must have the same parameters and returntype. A pointer initialized in this manner is called a null pointer. After numerous requests, ive finally come out with this pdf version which is identical. Callbacks in c a callback is any executable code that is passed as an argument to other code, which is expected to call back execute the argument at a given time source. They can be used to allow variability in the function that is to be called, at runtime. C programmingpointers and arrays wikibooks, open books for an. If there is no return value, specify a return type of void. C library provides standard functions for these that you can call, so no. In c, like normal data pointers int, char, etc, we can have pointers to functions. In the end it will give you an easy way to think about function pointers so their usage is more clear. If im not wrong we should not return a local variablepointer from a function, so i. Function pointers are an interesting and powerful tool but their syntax can be a little confusing.
Now, let us go ahead and create a function that will return pointer. Following is the function declaration syntax that will return pointer. In simple language, if a reference of a function is passed to another function as an argument to call it, then it will be called as a callback function. Similarly, c also allows to return a pointer from a function. Often, the function name will begin with new for this. To do so, you would have to declare a function returning a pointer as in the following example. In c, we can use function pointers to avoid code redundancy. We have seen in the last chapter how c programming allows to return an array from a function. Function returning pointer to user defined data type in c.
Second point to remember is that, it is not good idea to return the address of a local variable to outside of the function, so you would have to define the local variable as static variable. Function returning pointer to user defined data type in c user defined data types are. Function returning pointer to derived data type in c. For example a simple qsort function can be used to sort arrays in ascending order or descending or by any other order in case of array of structures. To declare a function returning a pointer to a function, first write the declaration of the function type to be returned. Functions pointers in c programming with examples guru99. The returning of a struct, or of a pointer to a struct, is common when dynamically creating new elements during the time a program is run. C allows a function to return a pointer to local variable, static variable. With pointer parameters, our functions now can process actual data rather than a copy of data. In order to modify the actual values of variables, the calling statement passes addresses to pointer parameters in a function. C programming ppt slides and pdf for functions, arrays and. So return type of function can be pointer to array, pointer to function and pointer to pointer.