What does this C snippet mean?

Question

I'm a noob at shellcodes and I'm trying to understand all scenarios. I have found many codes to test my shellcodes in C, but to my surprise they are very unreadeable and I can't understand neither this code:

int (*func)();
func = (int (*)()) code;
(int)(*func)();

Or this one:

int (*ret)() = (int(*)())code;
ret();

Is this an equivalent to eval() in Javascript? And how doest it work?

OP can you confirm whether you mean to ask about C and C++, or just C? (I see from the edit history that someone deleted mention of C++ for no apparent reason) — M.M, Nov 21 '17 at 01:13
My reason is because I was not sure if this snippet is in C or C++, users corrected me to chage to C. — Cami Rodriguez, Nov 21 '17 at 01:18

Bo Persson · Accepted Answer · 2017-11-21T00:59:32.467

int (*func)(); is a pointer to a function (taking no parameters in C++) that returns an int.

(*func)(); or just func(); calls the function pointed to.

(int (*)()) code; is a nasty type cast telling the compiler that code is pointing to such a function. If it is not, but you still try to call the function, the program is invalid and anything can happen.

"Anything" includes actually executing the shell code, or crashing, or something else. The language standard doesn't say.

What does this C snippet mean?

1 Answers1