Hacker News Reader

Comment by rwmj | Hacker News Reader

Golang gets this wrong. It should be scope-level not function-level (or perhaps there should be two different types, but I have never personally had a need for a function-level cleanup).

Edit: Also please review how attribute cleanup is used by existing C code before jumping into proposals. If something is added to C2x which is inconsistent with what existing code is already doing widely, then it's no help to anyone.

View on HN

Yes, we have discussed adding this feature at scope level. A not entirely serious proposal was to implement it as follows:

  #define DEFER(a, b, c)  \
     for (bool _flag = true; _flag; _flag = false) \
     for (a; _flag && (b); c, _flag = false)

  int fun() {
     DEFER(FILE *f1 = fopen(...), (NULL != f1), mfclose(f1)) {
       DEFER(FILE *f2 = fopen(...), (NULL != f2), mfclose(f2)) {
         DEFER(FILE *f3 = fopen(...), (NULL != f3), mfclose(f3)) {
             ... do something ...
         }
       }
     }
  }

We are also looking at the attribute cleanup. Sounds like you should be involved in developing this proposal?

Yes, I'll ask around in Red Hat too, see if we can get some help with this.

Apropos of this, I'll toss in: please support do-after statements (and also let statements).

  do foo(); _After bar();
  /* exactly equivalent to (with gcc ({})s): */
  ({ bar(); foo(); });
  #define DEFER(a, b, c) \
    _Let(a) if(!b) {} else do {c;} _After

(This is in fact a entirely serious proposal, though I don't actually expect it to happen.)

Reply on news.ycombinator.com