* [PATCH v3] resolv/nss_dns/dns-host: Get rid of alloca.
@ 2023-08-14 14:10 Joe Simmons-Talbott
2023-08-14 14:23 ` Andreas Schwab
2023-08-14 14:23 ` Siddhesh Poyarekar
0 siblings, 2 replies; 5+ messages in thread
From: Joe Simmons-Talbott @ 2023-08-14 14:10 UTC (permalink / raw)
To: libc-alpha; +Cc: Joe Simmons-Talbott
Since the alloca is a small constant size use an array instead.
---
Changes to v2:
* Move tmp back into lower scope
resolv/nss_dns/dns-host.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
index 1d60c51f5e..160a017d42 100644
--- a/resolv/nss_dns/dns-host.c
+++ b/resolv/nss_dns/dns-host.c
@@ -395,8 +395,8 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
*/
if (strchr (name, '.') == NULL)
{
- char *tmp = alloca (NS_MAXDNAME);
- const char *cp = __res_context_hostalias (ctx, name, tmp, NS_MAXDNAME);
+ char tmp[NS_MAXDNAME];
+ const char *cp = __res_context_hostalias (ctx, name, tmp, sizeof (tmp));
if (cp != NULL)
name = cp;
}
--
2.39.2
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v3] resolv/nss_dns/dns-host: Get rid of alloca.
2023-08-14 14:10 [PATCH v3] resolv/nss_dns/dns-host: Get rid of alloca Joe Simmons-Talbott
@ 2023-08-14 14:23 ` Andreas Schwab
2023-08-14 14:28 ` Siddhesh Poyarekar
2023-08-14 14:23 ` Siddhesh Poyarekar
1 sibling, 1 reply; 5+ messages in thread
From: Andreas Schwab @ 2023-08-14 14:23 UTC (permalink / raw)
To: Joe Simmons-Talbott via Libc-alpha; +Cc: Joe Simmons-Talbott
On Aug 14 2023, Joe Simmons-Talbott via Libc-alpha wrote:
> diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
> index 1d60c51f5e..160a017d42 100644
> --- a/resolv/nss_dns/dns-host.c
> +++ b/resolv/nss_dns/dns-host.c
> @@ -395,8 +395,8 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
> */
> if (strchr (name, '.') == NULL)
> {
> - char *tmp = alloca (NS_MAXDNAME);
> - const char *cp = __res_context_hostalias (ctx, name, tmp, NS_MAXDNAME);
> + char tmp[NS_MAXDNAME];
> + const char *cp = __res_context_hostalias (ctx, name, tmp, sizeof (tmp));
> if (cp != NULL)
> name = cp;
> }
We don't tolerate undefined behaviour in glibc.
--
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v3] resolv/nss_dns/dns-host: Get rid of alloca.
2023-08-14 14:10 [PATCH v3] resolv/nss_dns/dns-host: Get rid of alloca Joe Simmons-Talbott
2023-08-14 14:23 ` Andreas Schwab
@ 2023-08-14 14:23 ` Siddhesh Poyarekar
1 sibling, 0 replies; 5+ messages in thread
From: Siddhesh Poyarekar @ 2023-08-14 14:23 UTC (permalink / raw)
To: Joe Simmons-Talbott, libc-alpha
On 2023-08-14 10:10, Joe Simmons-Talbott via Libc-alpha wrote:
> Since the alloca is a small constant size use an array instead.
> ---
> Changes to v2:
> * Move tmp back into lower scope
>
> resolv/nss_dns/dns-host.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
LGTM.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
>
> diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
> index 1d60c51f5e..160a017d42 100644
> --- a/resolv/nss_dns/dns-host.c
> +++ b/resolv/nss_dns/dns-host.c
> @@ -395,8 +395,8 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
> */
> if (strchr (name, '.') == NULL)
> {
> - char *tmp = alloca (NS_MAXDNAME);
> - const char *cp = __res_context_hostalias (ctx, name, tmp, NS_MAXDNAME);
> + char tmp[NS_MAXDNAME];
> + const char *cp = __res_context_hostalias (ctx, name, tmp, sizeof (tmp));
> if (cp != NULL)
> name = cp;
> }
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v3] resolv/nss_dns/dns-host: Get rid of alloca.
2023-08-14 14:23 ` Andreas Schwab
@ 2023-08-14 14:28 ` Siddhesh Poyarekar
2023-08-14 15:01 ` Joe Simmons-Talbott
0 siblings, 1 reply; 5+ messages in thread
From: Siddhesh Poyarekar @ 2023-08-14 14:28 UTC (permalink / raw)
To: Andreas Schwab, Joe Simmons-Talbott via Libc-alpha; +Cc: Joe Simmons-Talbott
On 2023-08-14 10:23, Andreas Schwab via Libc-alpha wrote:
> On Aug 14 2023, Joe Simmons-Talbott via Libc-alpha wrote:
>
>> diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
>> index 1d60c51f5e..160a017d42 100644
>> --- a/resolv/nss_dns/dns-host.c
>> +++ b/resolv/nss_dns/dns-host.c
>> @@ -395,8 +395,8 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
>> */
>> if (strchr (name, '.') == NULL)
>> {
>> - char *tmp = alloca (NS_MAXDNAME);
>> - const char *cp = __res_context_hostalias (ctx, name, tmp, NS_MAXDNAME);
>> + char tmp[NS_MAXDNAME];
>> + const char *cp = __res_context_hostalias (ctx, name, tmp, sizeof (tmp));
>> if (cp != NULL)
>> name = cp;
>> }
>
> We don't tolerate undefined behaviour in glibc.
>
Ah, sorry I hadn't noticed that cp escapes that scope. Joe, your v2 is
correct.
Thanks,
Sid
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v3] resolv/nss_dns/dns-host: Get rid of alloca.
2023-08-14 14:28 ` Siddhesh Poyarekar
@ 2023-08-14 15:01 ` Joe Simmons-Talbott
0 siblings, 0 replies; 5+ messages in thread
From: Joe Simmons-Talbott @ 2023-08-14 15:01 UTC (permalink / raw)
To: Siddhesh Poyarekar; +Cc: Andreas Schwab, Joe Simmons-Talbott via Libc-alpha
On Mon, Aug 14, 2023 at 10:28:07AM -0400, Siddhesh Poyarekar wrote:
> On 2023-08-14 10:23, Andreas Schwab via Libc-alpha wrote:
> > On Aug 14 2023, Joe Simmons-Talbott via Libc-alpha wrote:
> >
> > > diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
> > > index 1d60c51f5e..160a017d42 100644
> > > --- a/resolv/nss_dns/dns-host.c
> > > +++ b/resolv/nss_dns/dns-host.c
> > > @@ -395,8 +395,8 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
> > > */
> > > if (strchr (name, '.') == NULL)
> > > {
> > > - char *tmp = alloca (NS_MAXDNAME);
> > > - const char *cp = __res_context_hostalias (ctx, name, tmp, NS_MAXDNAME);
> > > + char tmp[NS_MAXDNAME];
> > > + const char *cp = __res_context_hostalias (ctx, name, tmp, sizeof (tmp));
> > > if (cp != NULL)
> > > name = cp;
> > > }
> >
> > We don't tolerate undefined behaviour in glibc.
> >
>
> Ah, sorry I hadn't noticed that cp escapes that scope. Joe, your v2 is
> correct.
I went ahead and posted a v4 patch moving tmp back up one scope level
[1]
[1] https://sourceware.org/pipermail/libc-alpha/2023-August/150906.html
Thanks,
Joe
^ permalink raw reply [flat|nested] 5+ messages in thread
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2023-08-14 14:10 [PATCH v3] resolv/nss_dns/dns-host: Get rid of alloca Joe Simmons-Talbott
2023-08-14 14:23 ` Andreas Schwab
2023-08-14 14:28 ` Siddhesh Poyarekar
2023-08-14 15:01 ` Joe Simmons-Talbott
2023-08-14 14:23 ` Siddhesh Poyarekar
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