How to execute a code in buffer?

Question

I was wondering if i could excute code that has been stored in a buffer. For Example :

char buffer[20] = "printf(\"Stackoverflow\");";

Is there way to execute the printf statement?

You must create your own because it does not have a mechanism to execute a statement dynamically in C. and buffer too small. — BLUEPIXY, Dec 24 '13 at 11:31
If ran through an [interpreter](http://stackoverflow.com/questions/584714/is-there-an-interpreter-for-c) you could make it happen. Or if you embed the interpreter into your app. — StoryTeller - Unslander Monica, Dec 24 '13 at 11:32

score 4 · Accepted Answer · edited May 23 '17 at 12:19

There is no eval-like construct in C as there is in some so-called scripting languages. As C is usually compiled to machine code and not interpreted at run-time, implementing such features would require a platform with some C compiler or C interpreter in order to make the program run.

You may take a look at this question: Is there an interpreter for C? and inspect the links there or search for C interpreters.

And as long as the strings you want to be executed are known at compile-time (i.e. you don't create them depending on some input) you can use function pointers:

void print_hello(void) {
    puts("Hello, world!");
}

void print_goodbye(void) {
    puts("Goodbye.");
}

int main(void) {
    void (*printer)(void) = print_hello;
    printer();
    printer = print_goodbye;
    printer();
    return 0;
}

where you may set printer to the address of any function (with a compatible type), so you don't need to know at compile-time which function eventually will be called.

HTH

How to execute a code in buffer?

1 Answers1