Unable to free const pointers in C

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

Answer

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);