free

There seem to be two arguments why one should set a pointer to NULL after freeing them. Avoid crashing when double-freeing pointers. Short: Calling free() a second time, by accident, doesn't crash when it's set to NULL . Almost always this masks a logical bug because there is no reason to call free() a second time. It's safer to let the application crash and be able to fix it. It's not guaranteed to crash because sometimes new memory is allocated at the same address. Double free occurs mostly when there are two pointers pointing to the same address. Logical errors can lead to data corruption

Should I free all my mallocated memory when I am exiting program in the due of error? something = (char**) malloc (x * sizeof(char*)); for (i = 0; i < x; i++) something[i] = (char*) malloc (y + 1); ... if (anything == NULL) { printf("Your input is wrong!"); // should I free memory of every mallocated entity now? exit(1); } else { // work with mallocated entities ... free(something); // it must be here system("pause); } It depends on the OS. Best practice I'd say you should explicitly free it. It also makes using tools like valgrind a PITA if you have memory not freed all over the place and I

If I allocated memory in my C program using malloc and now I want to exit, do I have to free the allocated memory, or can I assume that since my entire program terminates, it will be freed by the OS? I run in Linux environment. Any modern operating system will clean up everything after a process terminates, but it's generally not a good practice to rely on this. It depends on the program you are writing. If it's just a command line tool that runs and terminates quickly, you may not bother cleaning up. But be aware that it is this mindset that causes memory leaks in daemons and long-running

How can I free a const char* ? I allocated new memory using malloc , and when I'm trying to free it I always receive the error "incompatible pointer type" The code that causes this is something like: char* name="Arnold"; const char* str=(const char*)malloc(strlen(name)+1); free(str); // error here Several people have posted the right answer, but they keep deleting it for some reason. You need to cast it to a non-const pointer; free takes a void* , not a const void* : free((char*)str); Tim Post Your code is reversed. This: char* name="Arnold"; const char* str=(const char*)malloc(strlen(name)+1)

Say you have the following ANSI C code that initializes a multi-dimensional array : int main() { int i, m = 5, n = 20; int **a = malloc(m * sizeof(int *)); //Initialize the arrays for (i = 0; i < m; i++) { a[i]=malloc(n * sizeof(int)); } //...do something with arrays //How do I free the **a ? return 0; } After using the **a , how do I correctly free it from memory ? [Update] (Solution) Thanks to Tim's (and the others) answer , I can now do such a function to free up memory from my multi-dimensional array : void freeArray(int **a, int m) { int i; for (i = 0; i < m; ++i) { free(a[i]); } free(a);