Dereferencing a Function Pointer to Swap the Function

Question

I tried to redefine malloc() in order to use a custom allocator without modifying the code. Why doesn't the following code work? Is using #define the only left solution?

void *(*malloc_ptr)(size_t) = malloc;
*malloc_ptr = my_malloc;

Answer 1

In order to reliably replace the memory allocation library, use LD_PRELOAD and pass it your own implementation of malloc and free.

Clearly you can create your own variable called malloc_ptr and use that in all your functions, but be aware that other library functions will call the standard malloc .

Answer 2

There is no assignment operator for function designators.

If you want to assign one function pointer to another function pointer then you should write

malloc_ptr = my_malloc;