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Re: libc/stdlib/mallocr.c (unlink)
I mean circular in that you do not traverse the list
until you reach a NULL pointer as one should not exist. The last element
will end up pointing forward to the first and vice-versa. If there is one element,
it should point to itself and cannot be removed via unlink.
Take a look at the first() and last() operators for bins.
/* field-extraction macros */
#define first(b) ((b)->fd)
#define last(b) ((b)->bk)
There is also a comment about the chunk list being circular:
Chunks always begin on even word boundries, so the mem portion
(which is returned to the user) is also on an even word boundary, and
thus double-word aligned.
Free chunks are stored in circular doubly-linked lists, and look like this:
As Chris has pointed out, we need to understand why you are seeing a NULL
pointer in the list. There may be a serious logic flaw occuring or something
in your program may be stepping on storage.
-- Jeff J.
Earnie Boyd wrote:
What do you mean by ``circular''? If the pointer value is capable of
being zero it will SIGSEGV, on some systems, if referenced.
Earnie.
J. Johnston wrote:
Actually, you are entirely correct. I had forgotten that "both" the
chunk
and bin lists were circular. The change will be reverted.
Earnie, you are going to have to do some more investigating.
-- Jeff J.
Christopher Faylor wrote:
On Tue, Feb 18, 2003 at 05:35:14PM -0500, J. Johnston wrote:
Patch checked in, thanks.
Isn't this a "why is the pointer NULL?" type of situation? It seems
like
checking for null is papering over a possible problem.
cgf
------------------------------------------------------------------------
2003.02.18 Earnie Boyd <earnie at users dot sf dot net>
* libc/stdlib/mallocr.c (unlink): Don't assign a value to a
pointer
with a NULL value.
Index: mallocr.c
===================================================================
RCS file: /cvs/src/src/newlib/libc/stdlib/mallocr.c,v
retrieving revision 1.9
diff -u -3 -p -r1.9 mallocr.c
--- mallocr.c 11 Oct 2002 10:28:30 -0000 1.9
+++ mallocr.c 18 Feb 2003 21:40:05 -0000
@@ -1936,8 +1936,8 @@ static void do_check_malloced_chunk(p, s
{
\
BK =
P->bk; \
FD =
P->fd; \
- FD->bk =
BK; \
- BK->fd =
FD; \
+ if (FD) FD->bk =
BK; \
+ if (BK) BK->fd =
FD; \
}
\
/* Place p as the last remainder */