[PATCH] include: linux/iopoll: fix uninitialized warning

[PATCH] include: linux/iopoll: fix uninitialized warning

[Rouven Czerwinski]

In gcc 13.3 there is a warning that start may be used unitialized:

  include/linux/iopoll.h:42:21: warning: ‘start’ may be used uninitialized [-Wmaybe-uninitialized]
     42 |                     is_timeout(start, ((timeout_us) * USECOND))) { \
        |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The warning is bogus since before usage of start !IN_PBL and
timeout_us != 0 are checked for the case where start is used, but in
this case it is also always initialized to get_time_ns().
Initialize it to zero to silence the warning.

Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
---
 include/linux/iopoll.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/iopoll.h b/include/linux/iopoll.h
index 96b17dee48..c7dcaec382 100644
--- a/include/linux/iopoll.h
+++ b/include/linux/iopoll.h
@@ -31,7 +31,7 @@
  */
 #define read_poll_timeout(op, val, cond, timeout_us, args...)	\
 ({ \
-	uint64_t start; \
+	uint64_t start = 0; \
 	if (!IN_PBL && (timeout_us) != 0) \
 		start = get_time_ns(); \
 	for (;;) { \
-- 
2.46.0

Re: [PATCH] include: linux/iopoll: fix uninitialized warning

[Sascha Hauer]

On Tue, 03 Sep 2024 11:37:12 +0200, Rouven Czerwinski wrote:
> In gcc 13.3 there is a warning that start may be used unitialized:
> 
>   include/linux/iopoll.h:42:21: warning: ‘start’ may be used uninitialized [-Wmaybe-uninitialized]
>      42 |                     is_timeout(start, ((timeout_us) * USECOND))) { \
>         |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> The warning is bogus since before usage of start !IN_PBL and
> timeout_us != 0 are checked for the case where start is used, but in
> this case it is also always initialized to get_time_ns().
> Initialize it to zero to silence the warning.
> 
> [...]

Applied, thanks!

[1/1] include: linux/iopoll: fix uninitialized warning
      https://git.pengutronix.de/cgit/barebox/commit/?id=7485dad4a06c (link may not be stable)

Best regards,
-- 
Sascha Hauer <s.hauer@pengutronix.de>

Re: [PATCH] include: linux/iopoll: fix uninitialized warning

[Ahmad Fatoum]

Hello Rouven,

On 03.09.24 11:37, Rouven Czerwinski wrote:
> In gcc 13.3 there is a warning that start may be used unitialized:
> 
>   include/linux/iopoll.h:42:21: warning: ‘start’ may be used uninitialized [-Wmaybe-uninitialized]
>      42 |                     is_timeout(start, ((timeout_us) * USECOND))) { \
>         |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> The warning is bogus since before usage of start !IN_PBL and
> timeout_us != 0 are checked for the case where start is used, but in
> this case it is also always initialized to get_time_ns().
> Initialize it to zero to silence the warning.

FTR: Here's the GCC bugzilla report about this false positive:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98049

Thanks for the workaround,
Ahmad

> 
> Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
> ---
>  include/linux/iopoll.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/iopoll.h b/include/linux/iopoll.h
> index 96b17dee48..c7dcaec382 100644
> --- a/include/linux/iopoll.h
> +++ b/include/linux/iopoll.h
> @@ -31,7 +31,7 @@
>   */
>  #define read_poll_timeout(op, val, cond, timeout_us, args...)	\
>  ({ \
> -	uint64_t start; \
> +	uint64_t start = 0; \
>  	if (!IN_PBL && (timeout_us) != 0) \
>  		start = get_time_ns(); \
>  	for (;;) { \


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