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bug#25332: [PATCH] Change while loops to for loops.


From: Chris Gregory
Subject: bug#25332: [PATCH] Change while loops to for loops.
Date: Sun, 8 Jan 2017 13:24:04 -0800

There are places in ralloc.c where a for loop is used to express a loop, and places where a while loop is used with the increment operation at the end of it.  This would just simplify all code so that it was consistently using a for loop for this purpose.

Without this patch here is a good usage of for:

  heap_ptr heap;

  for (heap = last_heap; heap; heap = heap->prev)
    {
      if (heap->start <= address && address <= heap->end)
return heap;
    }

Here is a usage of while that should be a for loop like the previous example:

  bloc_ptr p = first_bloc;

  while (p != NIL_BLOC)
    {
      /* Consistency check. Don't return inconsistent blocs.
Don't abort here, as callers might be expecting this, but
callers that always expect a bloc to be returned should abort
if one isn't to avoid a memory corruption bug that is
difficult to track down.  */
      if (p->variable == ptr && p->data == *ptr)
return p;

      p = p->next;
    }

Recommended new code:

  bloc_ptr p;

  for (p = first_bloc; p != NIL_BLOC; p = p->next)
    {
      /* Consistency check. Don't return inconsistent blocs.
Don't abort here, as callers might be expecting this, but
callers that always expect a bloc to be returned should abort
if one isn't to avoid a memory corruption bug that is
difficult to track down.  */
      if (p->variable == ptr && p->data == *ptr)
return p;
    }

This style exact loop is even used later on (line 509 in update_heap_bloc_correspondence()):

  /* Advance through blocs one by one.  */
  for (b = bloc; b != NIL_BLOC; b = b->next)

-- 
Chris Gregory

On Sat, Jan 7, 2017 at 12:30 AM, Eli Zaretskii <address@hidden> wrote:
tags 25332 notabug
close 25332
thanks

> From: Chris Gregory <address@hidden>
> Date: Mon, 02 Jan 2017 00:26:07 -0800
>
> This patch changes while loops to for loops to make the code more
> consistent.

I don't think I understand the rationale.  Why is using 'while'
inconsistent?

In any case, please don't bother making style changes in ralloc.c, as
that file should almost never be used in Emacs, except in some
marginal configurations, and we actually would like to get rid of it
altogether.  It's therefore a waste of effort to try to make its style
better.


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