Re: [Intel-gfx] [PATCH i-g-t 3/6] igt/core: Fix build warning

[Petri Latvala <petri.latvala@intel.com>]

On Fri, Nov 19, 2021 at 12:59:42PM +0000, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> 
> .../lib/igt_thread.c: In function ‘__igt_unique____igt_constructor_l66’:
> .../lib/igt_thread.c:68:9: warning: ‘pthread_setspecific’ expecting 1 byte in a region of size 0 [-Wstringop-overread]
>    68 |         pthread_setspecific(__igt_is_main_thread, (void*) 0x1);
>       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Petri Latvala <petri.latvala@intel.com>
> ---
>  lib/igt_core.c   | 6 ++++--
>  lib/igt_thread.c | 4 +++-
>  2 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/igt_core.c b/lib/igt_core.c
> index ec05535cd56e..acb9743c4a24 100644
> --- a/lib/igt_core.c
> +++ b/lib/igt_core.c
> @@ -2752,6 +2752,8 @@ void igt_vlog(const char *domain, enum igt_log_level level, const char *format,
>  	char *line, *formatted_line;
>  	char *thread_id;
>  	const char *program_name;
> +	const uintptr_t false_key = 0;
> +	const uintptr_t true_key = 1;
>  	const char *igt_log_level_str[] = {
>  		"DEBUG",
>  		"INFO",
> @@ -2796,9 +2798,9 @@ void igt_vlog(const char *domain, enum igt_log_level level, const char *format,
>  	}
>  
>  	if (line[strlen(line) - 1] == '\n')
> -		pthread_setspecific(__vlog_line_continuation, (void*) false);
> +		pthread_setspecific(__vlog_line_continuation, &false_key);
>  	else
> -		pthread_setspecific(__vlog_line_continuation, (void*) true);
> +		pthread_setspecific(__vlog_line_continuation, &true_key);

Quoting the usage of this:
        if (pthread_getspecific(__vlog_line_continuation)) {

That's going to give a non-null pointer in both cases.



>  
>  	/* append log buffer */
>  	_igt_log_buffer_append(formatted_line);
> diff --git a/lib/igt_thread.c b/lib/igt_thread.c
> index 5bdda4102def..f5de2d57eaaa 100644
> --- a/lib/igt_thread.c
> +++ b/lib/igt_thread.c
> @@ -64,6 +64,8 @@ bool igt_thread_is_main(void)
>  }
>  
>  igt_constructor {
> +	const uintptr_t key = 1;
> +
>  	pthread_key_create(&__igt_is_main_thread, NULL);
> -	pthread_setspecific(__igt_is_main_thread, (void*) 0x1);
> +	pthread_setspecific(__igt_is_main_thread, &key);

This is fine, __igt_is_main_thread key will have non-null only on the
main thread. But still a bit sus slapping the address of a
function-local variable to setspecific, we might just be trading a
compiler warning for a new future one.


-- 
Petri Latvala


>  }
> -- 
> 2.32.0
>