Re: [PATCH 2/3] tools/vm/page-types: suppress gcc warnings

[David Rientjes]

On Tue, 10 Nov 2015, Sergey Senozhatsky wrote:

> Define 'end' and 'first' as volatile to suppress
> gcc warnings:
> 
> page-types.c:854:13: warning: variable 'end' might be
>    clobbered by 'longjmp' or 'vfork' [-Wclobbered]
> page-types.c:858:6: warning: variable 'first' might be
>    clobbered by 'longjmp' or 'vfork' [-Wclobbered]
> 
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
> ---
>  tools/vm/page-types.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/vm/page-types.c b/tools/vm/page-types.c
> index bcf5ec7..0651cd5 100644
> --- a/tools/vm/page-types.c
> +++ b/tools/vm/page-types.c
> @@ -851,11 +851,12 @@ static void walk_file(const char *name, const struct stat *st)
>  	uint8_t vec[PAGEMAP_BATCH];
>  	uint64_t buf[PAGEMAP_BATCH], flags;
>  	unsigned long nr_pages, pfn, i;
> -	off_t off, end = st->st_size;
> +	off_t off;
>  	int fd;
>  	ssize_t len;
>  	void *ptr;
> -	int first = 1;
> +	volatile int first = 1;
> +	volatile off_t end = st->st_size;
>  
>  	fd = checked_open(name, O_RDONLY|O_NOATIME|O_NOFOLLOW);
>  

This can't possibly be correct, the warnings are legitimate and the result 
of the sigsetjmp() in the function.  You may be interested in 
returns_twice rather than marking random automatic variables as volatile.
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