2018-03-19 05:56:22

by Sergey Senozhatsky

Subject: [PATCH] tools: Fix str_error_r() Werror=restrict build

Commit c8b5f2c96d1bf6c ("tools: Introduce str_error_r()") added
an str_error_r() wrapper which makes gcc8 unhappy due to
restrict-qualified parameter aliasing violation:

../lib/str_error_r.c: In function ‘str_error_r’:
../lib/str_error_r.c:25:3: error: passing argument 1 to restrict-qualified parameter aliases with argument 5 [-Werror=restrict]
snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);
^~~~~~~~
cc1: all warnings being treated as errors

Workaround that aliasing error by creating an additional stack
variable which holds the buf pointer value we passed to strerror_r().

Signed-off-by: Sergey Senozhatsky <[email protected]>
---
tools/lib/str_error_r.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/lib/str_error_r.c b/tools/lib/str_error_r.c
index d6d65537b0d9..11c3425f272b 100644
--- a/tools/lib/str_error_r.c
+++ b/tools/lib/str_error_r.c
@@ -21,7 +21,12 @@
char *str_error_r(int errnum, char *buf, size_t buflen)
{
int err = strerror_r(errnum, buf, buflen);
- if (err)
- snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);
+ if (err) {
+ char *err_buf = buf;
+
+ snprintf(err_buf, buflen,
+ "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d",
+ errnum, buf, buflen, err);
+ }
return buf;
}
--
2.16.2

2018-03-19 07:20:00

by Jiri Olsa

Subject: Re: [PATCH] tools: Fix str_error_r() Werror=restrict build

On Mon, Mar 19, 2018 at 02:55:04PM +0900, Sergey Senozhatsky wrote:
> Commit c8b5f2c96d1bf6c ("tools: Introduce str_error_r()") added
> an str_error_r() wrapper which makes gcc8 unhappy due to
> restrict-qualified parameter aliasing violation:
>
> ../lib/str_error_r.c: In function ‘str_error_r’:
> ../lib/str_error_r.c:25:3: error: passing argument 1 to restrict-qualified parameter aliases with argument 5 [-Werror=restrict]
> snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);
> ^~~~~~~~
> cc1: all warnings being treated as errors
>
> Workaround that aliasing error by creating an additional stack
> variable which holds the buf pointer value we passed to strerror_r().
>
> Signed-off-by: Sergey Senozhatsky <[email protected]>

Josh posted another way to fix it:
https://marc.info/?l=linux-kernel&m=152116992412107&w=2

your patch keeps the same output, I dont mind either way ;-)

jirka


> ---
> tools/lib/str_error_r.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/str_error_r.c b/tools/lib/str_error_r.c
> index d6d65537b0d9..11c3425f272b 100644
> --- a/tools/lib/str_error_r.c
> +++ b/tools/lib/str_error_r.c
> @@ -21,7 +21,12 @@
> char *str_error_r(int errnum, char *buf, size_t buflen)
> {
> int err = strerror_r(errnum, buf, buflen);
> - if (err)
> - snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);
> + if (err) {
> + char *err_buf = buf;
> +
> + snprintf(err_buf, buflen,
> + "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d",
> + errnum, buf, buflen, err);
> + }
> return buf;
> }
> --
> 2.16.2
>

2018-03-19 07:46:11

by Sergey Senozhatsky

Subject: Re: [PATCH] tools: Fix str_error_r() Werror=restrict build

On (03/19/18 08:18), Jiri Olsa wrote:
> On Mon, Mar 19, 2018 at 02:55:04PM +0900, Sergey Senozhatsky wrote:
> > Commit c8b5f2c96d1bf6c ("tools: Introduce str_error_r()") added
> > an str_error_r() wrapper which makes gcc8 unhappy due to
> > restrict-qualified parameter aliasing violation:
> >
> > ../lib/str_error_r.c: In function ‘str_error_r’:
> > ../lib/str_error_r.c:25:3: error: passing argument 1 to restrict-qualified parameter aliases with argument 5 [-Werror=restrict]
> > snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);
> > ^~~~~~~~
> > cc1: all warnings being treated as errors
> >
> > Workaround that aliasing error by creating an additional stack
> > variable which holds the buf pointer value we passed to strerror_r().
> >
> > Signed-off-by: Sergey Senozhatsky <[email protected]>
>
> Josh posted another way to fix it:
> https://marc.info/?l=linux-kernel&m=152116992412107&w=2

Oh, thanks for the pointers.

> your patch keeps the same output, I dont mind either way ;-)

Thanks. No strong opinion, either way is OK :) Can't tell for sure if
snprintf(... "%p", buf) is significantly better than snprintf(... "[buf]"),
but Arnaldo wanted to have the first version.

-ss

2018-03-19 14:25:15

by Sergey Senozhatsky

Subject: Re: [PATCH] tools: Fix str_error_r() Werror=restrict build

On (03/19/18 11:16), Arnaldo Carvalho de Melo wrote:
> Em Mon, Mar 19, 2018 at 02:55:04PM +0900, Sergey Senozhatsky escreveu:
> > Commit c8b5f2c96d1bf6c ("tools: Introduce str_error_r()") added
> > an str_error_r() wrapper which makes gcc8 unhappy due to
> > restrict-qualified parameter aliasing violation:
> >
> > ../lib/str_error_r.c: In function ‘str_error_r’:
> > ../lib/str_error_r.c:25:3: error: passing argument 1 to restrict-qualified parameter aliases with argument 5 [-Werror=restrict]
> > snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);
> > ^~~~~~~~
> > cc1: all warnings being treated as errors
>
> I applied Josh's patch, just printing '[buf]', that is good enough, I
> think.

Sure. Do you need the whole "strerror_r(%d, %p, %zd)" in this case?
Seems that printing out just `errnum' should be good enough.

-ss

2018-03-19 14:53:24

by Arnaldo Carvalho de Melo

Subject: Re: [PATCH] tools: Fix str_error_r() Werror=restrict build

Em Mon, Mar 19, 2018 at 02:55:04PM +0900, Sergey Senozhatsky escreveu:
> Commit c8b5f2c96d1bf6c ("tools: Introduce str_error_r()") added
> an str_error_r() wrapper which makes gcc8 unhappy due to
> restrict-qualified parameter aliasing violation:
>
> ../lib/str_error_r.c: In function ‘str_error_r’:
> ../lib/str_error_r.c:25:3: error: passing argument 1 to restrict-qualified parameter aliases with argument 5 [-Werror=restrict]
> snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);
> ^~~~~~~~
> cc1: all warnings being treated as errors

I applied Josh's patch, just printing '[buf]', that is good enough, I
think.

- Arnaldo

> Workaround that aliasing error by creating an additional stack
> variable which holds the buf pointer value we passed to strerror_r().
>
> Signed-off-by: Sergey Senozhatsky <[email protected]>
> ---
> tools/lib/str_error_r.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/str_error_r.c b/tools/lib/str_error_r.c
> index d6d65537b0d9..11c3425f272b 100644
> --- a/tools/lib/str_error_r.c
> +++ b/tools/lib/str_error_r.c
> @@ -21,7 +21,12 @@
> char *str_error_r(int errnum, char *buf, size_t buflen)
> {
> int err = strerror_r(errnum, buf, buflen);
> - if (err)
> - snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);
> + if (err) {
> + char *err_buf = buf;
> +
> + snprintf(err_buf, buflen,
> + "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d",
> + errnum, buf, buflen, err);
> + }
> return buf;
> }
> --
> 2.16.2