Question

I’m using a web based application to grade a C program submitted by a student. For some questions, I would like the student to fill a code in a function. The following is an example screen that the student will see.

go() {
---------------------------------
|                               |
|                               |
|                               |
---------------------------------
}

main() {
  go() 
}

The student should fill some code inside a box. However, I don’t want the student to create a new function like this:

go() {
---------------------------------
|  go_help();                   |
| }                             |
| go_help() { printf("hi"); }   |
---------------------------------
}

main() {
  go() 
}

How can I prevent the student to create a new function? The code template together with the code filled by the student will be sent to the queue waiting to be compiled and run by the server. I cannot change or check the code in that queue. The only thing I can do is to change the code template.

Answer 1

I think catching this at compile time will be very difficult (if not impossible). However, I you’re willing to settle with a runtime error, the following might work (tested on GCC):

void go() {
---------------------------------
|                               |
|                               |
|                               |
---------------------------------
    //make sure nobody redefines __func__ ...
    #undef __func__
    //... and __builtin_strcmp
    #undef __builtin_strcmp
    //check if we're still inside go()
    assert(__builtin_strcmp(__func__, "go") == 0);
}

int main() {
    go(); 
}