I just learned about function pointers (pointers pointing at the adress where where the machine code of a function is stored). This made me think about machine code and how it is stored in memory.
Is the machine code stored consecutively in memory, so that it is possible to "manually" increase the pointer until it points to the following/previous function?
Is this, what a debugger does? He lets me "see" where the program counter is pointing in the machine code?
Conclusion: one can program with function pointers a primitive debugger?
Did I understand this right, or am I way off?
Kind of. You are assuming functions will be layed out in memory the same way they are in the source code. Most likely, they will not be - the compiler usually moves them around all willy-nilly.
What you could do, however, is step through the code with a pointer to the current instruction, and increment that counter by a certain amount to get to the next instruction. However, in that case we would no longer call it a function pointer, since it's not just pointing to the beginning of a function; instead, we'd call it an instruction pointer.
In fact, this is exactly how a computer works - it has a special register called the program counter which always points to the current instruction, and increments it by a certain amount after every instruction (a GOTO command is equivalent to writing a value into the program counter).
In the real world, however, this is not how debuggers work - in fact, I'm not even sure if it's possible to have a pointer point to the code-segment in memory in C, other than a function pointer. More likely, you would only need to use this technique if you needed to simulate a program counter, such as writing an emulator for another processor-type.