Re: emacs' turn: remove useless if-before-free tests

[Jim Meyering]

Emanuele Giaquinta <address@hidden> wrote:
> On Mon, Jun 02, 2008 at 08:14:18AM +0200, Jim Meyering wrote:
>
>> Stefan Monnier <address@hidden> wrote:
>> > Sounds like a good cleanup.
>> > Feel free to install it unless there's a strong objection.
>>
>> Thanks.  I've committed those three change sets.
>
> This patch introduced a problem on os x, free on os x is redirected to
> unexmacosx.c:unexec_free, which does not support a NULL argument in an
> undumped emacs. The attached patch changes the problematic free call to
> xfree, as done a few lines below for another pointer.
>
> Emanuele
>
> diff --git a/src/lread.c b/src/lread.c
> index e5e77bc..3e0bd1f 100644
> --- a/src/lread.c
> +++ b/src/lread.c
> @@ -1269,7 +1269,7 @@ Return t if the file exists and loads successfully.  */)
>
>    UNGCPRO;
>
> -  free (saved_doc_string);
> +  xfree (saved_doc_string);
>    saved_doc_string = 0;
>    saved_doc_string_size = 0;

Thanks for catching and fixing that.
If using xfree (with its MALLOC_BLOCK_INPUT guard) is important there,
as it seems to be, then your patch also fixes a platform-independent
race condition bug.

The following change is probably a good idea, too.
It makes unexec_free (NULL) a no-op, just like free (NULL) is:

2008-06-08  Jim Meyering  <address@hidden>

        make unexec_free handle NULL the same way free does
        * unexmacosx.c (unexec_free): Ignore a NULL argument.

diff --git a/src/unexmacosx.c b/src/unexmacosx.c
index 4662260..57f70f8 100644
--- a/src/unexmacosx.c
+++ b/src/unexmacosx.c
@@ -1318,6 +1318,8 @@ unexec_realloc (void *old_ptr, size_t new_size)
 void
 unexec_free (void *ptr)
 {
+  if (ptr == NULL)
+    return;
   if (in_dumped_exec)
     {
       if (!ptr_in_unexec_regions (ptr))
--
1.5.6.rc1.23.g2f46