Changing code at runtime

Question

I have a pointer to a function (which i get from a vtable) and I want to edit the function by changing the assembler code (changing a few bytes) at runtime. I tried using memset and also tried assigning the new value directly (something like mPtr[0] = X, mPtr[1] = Y etc.) but I keep getting segmentation fault. How can I change the code?

(I'm using C++)

OS is windows.

Answer 1

In generally: if memory is allocated with API call VirtualAlloc than you can change the memory attributes with API call VirtualProtect. Check first memory attributes with API call VirtualQuery