* [musl] [PATCH 1/1] reallocarray casting overflow check explicitally
@ 2021-05-10 19:48 David CARLIER
2021-05-11 7:33 ` Szabolcs Nagy
0 siblings, 1 reply; 3+ messages in thread
From: David CARLIER @ 2021-05-10 19:48 UTC (permalink / raw)
To: musl
[-- Attachment #1: Type: text/plain, Size: 1 bytes --]
[-- Attachment #2: 0001-reallocarray-overflow-check-cast-to-size_t.patch --]
[-- Type: text/x-patch, Size: 638 bytes --]
From 04e3caa580cfe501ad00d85d63040de329962823 Mon Sep 17 00:00:00 2001
From: David Carlier <devnexen@gmail.com>
Date: Mon, 10 May 2021 20:45:12 +0100
Subject: [PATCH] reallocarray overflow check cast to size_t
---
src/malloc/reallocarray.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/malloc/reallocarray.c b/src/malloc/reallocarray.c
index 4a6ebe46..2556c917 100644
--- a/src/malloc/reallocarray.c
+++ b/src/malloc/reallocarray.c
@@ -4,7 +4,7 @@
void *reallocarray(void *ptr, size_t m, size_t n)
{
- if (n && m > -1 / n) {
+ if (n && m > (size_t)-1 / n) {
errno = ENOMEM;
return 0;
}
--
2.20.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [musl] [PATCH 1/1] reallocarray casting overflow check explicitally
2021-05-10 19:48 [musl] [PATCH 1/1] reallocarray casting overflow check explicitally David CARLIER
@ 2021-05-11 7:33 ` Szabolcs Nagy
2021-05-11 13:03 ` Rich Felker
0 siblings, 1 reply; 3+ messages in thread
From: Szabolcs Nagy @ 2021-05-11 7:33 UTC (permalink / raw)
To: David CARLIER, g; +Cc: musl
* David CARLIER <devnexen@gmail.com> [2021-05-10 20:48:26 +0100]:
> From 04e3caa580cfe501ad00d85d63040de329962823 Mon Sep 17 00:00:00 2001
> From: David Carlier <devnexen@gmail.com>
> Date: Mon, 10 May 2021 20:45:12 +0100
> Subject: [PATCH] reallocarray overflow check cast to size_t
>
> ---
> src/malloc/reallocarray.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/malloc/reallocarray.c b/src/malloc/reallocarray.c
> index 4a6ebe46..2556c917 100644
> --- a/src/malloc/reallocarray.c
> +++ b/src/malloc/reallocarray.c
> @@ -4,7 +4,7 @@
>
> void *reallocarray(void *ptr, size_t m, size_t n)
> {
> - if (n && m > -1 / n) {
> + if (n && m > (size_t)-1 / n) {
you need to explain this change more i think.
the usual arithmetic conversion rules of c already convert both
operands of / to size_t, unless size_t has lower conversion rank
than signed int, but such a system would have problems because
size_t was always promoted to int so you would need a lot more
casts in musl (and other software) to avoid signed int overflow
and negative arithmetics.
> errno = ENOMEM;
> return 0;
> }
> --
> 2.20.1
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [musl] [PATCH 1/1] reallocarray casting overflow check explicitally
2021-05-11 7:33 ` Szabolcs Nagy
@ 2021-05-11 13:03 ` Rich Felker
0 siblings, 0 replies; 3+ messages in thread
From: Rich Felker @ 2021-05-11 13:03 UTC (permalink / raw)
To: David CARLIER, g, musl
On Tue, May 11, 2021 at 09:33:06AM +0200, Szabolcs Nagy wrote:
> * David CARLIER <devnexen@gmail.com> [2021-05-10 20:48:26 +0100]:
> > From 04e3caa580cfe501ad00d85d63040de329962823 Mon Sep 17 00:00:00 2001
> > From: David Carlier <devnexen@gmail.com>
> > Date: Mon, 10 May 2021 20:45:12 +0100
> > Subject: [PATCH] reallocarray overflow check cast to size_t
> >
> > ---
> > src/malloc/reallocarray.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/src/malloc/reallocarray.c b/src/malloc/reallocarray.c
> > index 4a6ebe46..2556c917 100644
> > --- a/src/malloc/reallocarray.c
> > +++ b/src/malloc/reallocarray.c
> > @@ -4,7 +4,7 @@
> >
> > void *reallocarray(void *ptr, size_t m, size_t n)
> > {
> > - if (n && m > -1 / n) {
> > + if (n && m > (size_t)-1 / n) {
>
> you need to explain this change more i think.
>
> the usual arithmetic conversion rules of c already convert both
> operands of / to size_t, unless size_t has lower conversion rank
> than signed int, but such a system would have problems because
> size_t was always promoted to int so you would need a lot more
> casts in musl (and other software) to avoid signed int overflow
> and negative arithmetics.
I think the idea was just to make it explicit, but generally casting
is discouraged in musl. The corresponding code in calloc has a cast
but it's a historical artifact and contrary to the coding style used
throughout most of the source.
Rich
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-05-11 13:04 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-05-10 19:48 [musl] [PATCH 1/1] reallocarray casting overflow check explicitally David CARLIER
2021-05-11 7:33 ` Szabolcs Nagy
2021-05-11 13:03 ` Rich Felker
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).