From: Jens Gustedt <jens.gustedt@inria.fr>
To: Ariadne Conill <ariadne@dereferenced.org>
Cc: musl@lists.openwall.com
Subject: Re: [musl] [PATCH v3] implement recallocarray(3)
Date: Sun, 2 Aug 2020 12:09:58 +0200 [thread overview]
Message-ID: <20200802120958.19ba400a@inria.fr> (raw)
In-Reply-To: <20200801214216.10452-1-ariadne@dereferenced.org>
[-- Attachment #1: Type: text/plain, Size: 2495 bytes --]
Hello,
on Sat, 1 Aug 2020 15:42:16 -0600 you (Ariadne Conill
<ariadne@dereferenced.org>) wrote:
> This OpenBSD extension is similar to reallocarray(3), but
> zero-initializes the new memory area.
>
> This extension is placed in _BSD_SOURCE, like
> reallocarray(3).
>
> Changes from v2:
> - drop overflow checking for old size
>
> Changes from v1:
> - use realloc() instead of reallocarray()
> ---
> include/stdlib.h | 1 +
> src/malloc/recallocarray.c | 27 +++++++++++++++++++++++++++
> 2 files changed, 28 insertions(+)
> create mode 100644 src/malloc/recallocarray.c
>
> diff --git a/include/stdlib.h b/include/stdlib.h
> index b54a051f..a0412ad4 100644
> --- a/include/stdlib.h
> +++ b/include/stdlib.h
> @@ -146,6 +146,7 @@ int clearenv(void);
> #define WCOREDUMP(s) ((s) & 0x80)
> #define WIFCONTINUED(s) ((s) == 0xffff)
> void *reallocarray (void *, size_t, size_t);
> +void *recallocarray (void *, size_t, size_t, size_t);
> #endif
>
> #ifdef _GNU_SOURCE
> diff --git a/src/malloc/recallocarray.c b/src/malloc/recallocarray.c
> new file mode 100644
> index 00000000..a7827604
> --- /dev/null
> +++ b/src/malloc/recallocarray.c
> @@ -0,0 +1,27 @@
> +#define _BSD_SOURCE
> +#include <errno.h>
> +#include <stdlib.h>
> +#include <string.h>
> +
> +void *recallocarray(void *ptr, size_t om, size_t m, size_t n)
> +{
> + void *newptr;
> + size_t old_size = om * n, new_size;
> +
> + if (n && m > -1 / n) {
> + errno = ENOMEM;
> + return 0;
> + }
> + new_size = m * n;
> +
> + if (new_size <= old_size) {
> + memset((char *) ptr + new_size, 0, old_size -
> new_size);
> + }
> +
> + newptr = realloc(ptr, m * n);
I think, this would better be
newptr = realloc(ptr, new_size);
> + if (new_size > old_size) {
> + memset((char *) ptr + old_size, 0, new_size - old_size);
> + }
Generally, if `realloc` succeeds, access to the object behind `ptr` is
invalid, even if `ptr == newptr`.
Also `newptr` may be null if `realloc` fails, so this should read
if (newptr && new_size > old_size) {
memset((char *)newptr + old_size, 0, new_size - old_size);
}
Thanks
Jens
--
:: INRIA Nancy Grand Est ::: Camus ::::::: ICube/ICPS :::
:: ::::::::::::::: office Strasbourg : +33 368854536 ::
:: :::::::::::::::::::::: gsm France : +33 651400183 ::
:: ::::::::::::::: gsm international : +49 15737185122 ::
:: http://icube-icps.unistra.fr/index.php/Jens_Gustedt ::
[-- Attachment #2: Digitale Signatur von OpenPGP --]
[-- Type: application/pgp-signature, Size: 195 bytes --]
prev parent reply other threads:[~2020-08-02 10:10 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-01 21:42 Ariadne Conill
2020-08-02 8:07 ` Dmitry Samersoff
2020-08-02 8:51 ` Markus Wichmann
2020-08-02 10:09 ` Jens Gustedt [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200802120958.19ba400a@inria.fr \
--to=jens.gustedt@inria.fr \
--cc=ariadne@dereferenced.org \
--cc=musl@lists.openwall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).