Braiding the spaghetti: implementing defer in the preprocessor

Re:Braiding the spaghetti: implementing defer in the preproc... by andrewla on Monday September 16, 2024 @11:34AM (#41557110)

I love the idea of having a defer statement in general for C, but given the complexity of C scopes it's a little hard to wrangle (switch statements in particular break a lot of assumptions about how scopes should work).

I would prefer a directly scoped syntax similar for a for statement, something like

   defer (void * p = malloc(17); free(p)) {
     ...
   }

This gets more cumbersome as you have more such scopes in a function, but it gives a sane bounding. You can sort of do this now with a properly constructed for loop so that it cleans up on regular exit from the loop, but it can't handle exception exits (returns, breaks, and god forbid goto or longjmp).

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Re:Braiding the spaghetti: implementing defer in the preproc... by gustedt on Monday September 16, 2024 @11:55AM (#41557360)

This would be much more restrictive that what is proposed, because usually you would add `defer` statements as you go in a block, when you allocate more resources for example.

Also usually you should be able to have several actions,

  defer { 
    one; 
    two; 
  }

And the bounding in the proposed feature is sane, I think, it is the surrounding compound statement (AKA `{ ... }` block).

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