What is causing the read error?

Question

C++ / C#

The code:

unsigned char source[] = { ... };
    int sourceSize = sizeof(source);
    DWORD old_protect;
    VirtualProtect(&source, sourceSize, PAGE_EXECUTE_READWRITE, &old_protect);
    void(*f)() = (void(*)()) &source;
    f();

Problem:

Answer 1

You compile the function to binary and call it in place. So there are questions.
1. Did the functions provide the correct calling convention?
It seems to me that with such manual compilation it is easier to work with the PASCAL or STDCALL convention - well, the jester knows it.
2. VirtualProtect works with entire pages. So on a piece of memory from the data segment (well, or from the stack, I don’t see the full code), at best it will fail, at worst it will do nothing. Check if there was an error.
3. The first parameter must be source, not &source.

Answer 2

In addition to Mercury13, the penultimate line should be void(*f)() = (void(*)()) source;
In general, it is better to select a separate page, copy the shell there, and then call