Question

I think the following code is normal (and malloc/free is similar):

int foo(){

   FILE *fp = fopen("test.in", "r");

   int i;   

   for(i = 0; i < NUM; i ++){
       if(Match(fp, i)){    
            fclose(fp);
            return i;
       }
   }

   fclose(fp);
   return 0;
}

As we can see fclose(fp) appears twice in the code. It will appear more if there are other return statements in the function foo. However, it is troublesome that I have to write fclose(fp) many times. One solution is just one return for one function. However, multiple returns is sometimes useful. Is there any other solution?

PS: As I know, there is a macro(with-open-file) in lisp.

(with-open-file (stream-var open-argument*) 
    body-form*)

It could open and close file for us.

Answer 1

In the source code of linux kernel, there are many functions that have to take care of locks and other resource on return. And they conventionally add a cleanup label at the end of the function, and goto there whenever early return occurs. I personally recommend this usage to avoid duplicate code, and maybe this is the only sane usage of goto.