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Re: [RFC, PATCH] shrink struct vectorlike_header #2

From: Dmitry Antipov
Subject: Re: [RFC, PATCH] shrink struct vectorlike_header #2
Date: Wed, 07 Nov 2012 18:57:59 +0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121026 Thunderbird/16.0.2

On 11/06/2012 10:17 PM, Stefan Monnier wrote:

+/* When V is on the free list, first word after header is
+   used as a pointer to next vector on the free list.  */
+#define NEXT_IN_FREE_LIST(v)                           \
+  (*(struct Lisp_Vector **)((char *) v + header_size))
  /* Common shortcut to setup vector on a free list.  */

Why change the comment rather than the code.  IOW what don't you like in:

    Please make the code match the comment, e.g:
      (*(struct Lisp_Vector **)&(v->contents[0]))

I personally find it much more elegant and robust than doing pointer
arithmetic via conversion to char*.

I agree that your code looks better, but it causes 'dereferencing
type-punned pointer will break strict-aliasing rules' warning
(and so error if --enable-gcc-warnings, gcc 4.7.2).

The rest looks fine, tho it still probably lacks the corresponding
changes in .gdbinit, right?

Yes, it's still on the way...


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