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

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

[Sergey Senozhatsky]

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 <sergey.senozhatsky@gmail.com>
---
 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

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

[Jiri Olsa]

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 <sergey.senozhatsky@gmail.com>

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
> 

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

[Sergey Senozhatsky]

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 <sergey.senozhatsky@gmail.com>
> 
> 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

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

[Arnaldo Carvalho de Melo]

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 <sergey.senozhatsky@gmail.com>
> ---
>  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

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

[Sergey Senozhatsky]

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