From: "Harwath, Frederik" <frederik@codesourcery.com>
To: Thomas Schwinge <thomas@codesourcery.com>
Cc: Jakub Jelinek <jakub@redhat.com>,
Andrew Stubbs <ams@codesourcery.com>, <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] Add OpenACC acc_get_property support for AMD GCN
Date: Thu, 30 Jan 2020 08:04:00 -0000 [thread overview]
Message-ID: <ebcf8435-02ff-e3f3-8231-bc51b9fed046@codesourcery.com> (raw)
In-Reply-To: <87h80ema2b.fsf@euler.schwinge.homeip.net>
Hi Thomas,
On 29.01.20 18:44, Thomas Schwinge wrote:
>> + size_t len = sizeof hsa_context.driver_version_s;
>> + int printed = snprintf (hsa_context.driver_version_s, len,
>> + "HSA Runtime %hu.%hu", (unsigned short int)major,
>> + (unsigned short int)minor);
>> + if (printed >= len)
>> + GCN_WARNING ("HSA runtime version string was truncated."
>> + "Version %hu.%hu is too long.", (unsigned short int)major,
>> + (unsigned short int)minor);
>
> (Can it actually happen that 'snprintf' returns 'printed > len' --
> meaning that it's written into random memory? I thought 'snprintf' has a
> hard stop at 'len'? Or does this indicate the amount of memory it
> would've written? I should re-read the manpage at some point...) ;-)
>
Yes, "printed > len" can happen. Seems that I have chosen a bad variable name.
"actual_len" (of the formatted string that should have been written -
excluding the terminating '\0') would have been more appropriate.
> For 'printed = len' does or doesn't 'snprintf' store the terminating
> 'NUL' character, or do we manually have to set:
>
> hsa_context.driver_version_s[len - 1] = '\0';
>
> ... in that case?
No, in this case, the printed string is missing the last character, but the
terminating '\0' has been written. Consider:
#include <stdio.h>
int main () {
char s[] = "foo";
char buf[3];
// buf is too short to hold terminating '\0'
int actual_len = snprintf (buf, 3, "%s", s);
printf ("buf: %s\n", buf);
printf ("actual_len: %d\n", actual_len);
}
Output:
buf: fo
actual_len: 3
>
>> @@ -3410,15 +3432,19 @@ GOMP_OFFLOAD_init_device (int n)
>
>> - char buf[64];
>> status = hsa_fns.hsa_agent_get_info_fn (agent->id, HSA_AGENT_INFO_NAME,
>> - &buf);
>> + &agent->name);
>> if (status != HSA_STATUS_SUCCESS)
>> return hsa_error ("Error querying the name of the agent", status);
>
> (That's of course pre-existing, but) this looks like a dangerous API,
> given that 'hsa_agent_get_info_fn' doesn't know 'sizeof agent->name' (or
> 'sizeof buf' before)...
The API documentation
(cf. https://rocm-documentation.readthedocs.io/en/latest/ROCm_API_References/ROCr-API.html)
states that "the type of this attribute is a NUL-terminated char[64]".
But, right, should this ever change, we might not notice it.
Best regards,
Frederik
next prev parent reply other threads:[~2020-01-30 7:10 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-03 16:51 [PATCH, og8] Add OpenACC 2.6 `acc_get_property' support Maciej W. Rozycki
2018-12-05 10:12 ` Chung-Lin Tang
2018-12-05 18:17 ` Maciej W. Rozycki
2018-12-10 9:06 ` Chung-Lin Tang
2018-12-20 14:25 ` Maciej W. Rozycki
2019-01-08 17:42 ` Thomas Schwinge
2019-10-07 18:41 ` Thomas Schwinge
2019-11-05 15:09 ` Harwath, Frederik
2019-11-14 15:41 ` [PATCH] " Frederik Harwath
2019-12-16 23:06 ` Thomas Schwinge
2019-12-17 9:39 ` Martin Jambor
2019-12-17 9:47 ` Andrew Stubbs
2019-12-20 17:11 ` Harwath, Frederik
2019-12-21 23:01 ` Thomas Schwinge
2019-12-22 22:20 ` Harwath, Frederik
2020-01-10 23:44 ` Thomas Schwinge
2020-01-30 16:14 ` Make OpenACC 'acc_get_property' with 'acc_device_current' work (was: [PATCH] Add OpenACC 2.6 `acc_get_property' support) Thomas Schwinge
2020-02-03 12:16 ` Harwath, Frederik
2020-02-03 14:41 ` Make OpenACC 'acc_get_property' with 'acc_device_current' work Tobias Burnus
2020-01-16 16:03 ` [PATCH] Add OpenACC 2.6 `acc_get_property' support Thomas Schwinge
2020-01-20 14:20 ` Harwath, Frederik
2020-01-23 15:08 ` Thomas Schwinge
2020-01-24 9:36 ` Harwath, Frederik
2020-01-27 14:57 ` Fortran 'acc_get_property' return type (was: [PATCH] Add OpenACC 2.6 `acc_get_property' support) Thomas Schwinge
2020-01-28 15:31 ` [PATCH] Add OpenACC acc_get_property support for AMD GCN Harwath, Frederik
2020-01-28 16:14 ` Andrew Stubbs
2020-01-29 10:10 ` Harwath, Frederik
2020-01-29 11:07 ` Andrew Stubbs
2020-01-29 11:47 ` Harwath, Frederik
2020-01-29 17:58 ` Thomas Schwinge
2020-01-29 18:12 ` Andrew Stubbs
2020-01-30 8:04 ` Harwath, Frederik [this message]
2020-01-30 16:28 ` Thomas Schwinge
2020-01-30 16:54 ` Andrew Stubbs
2020-01-31 9:32 ` Thomas Schwinge
2020-01-31 12:32 ` Harwath, Frederik
2020-01-31 14:49 ` Thomas Schwinge
2020-04-29 9:19 ` [PATCH] Add OpenACC 2.6 `acc_get_property' support Thomas Schwinge
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