Re: [Minios-devel] [UNIKRAFT PATCHv3 24/25] nolibc: Clear a -Wstringop-overflow warning for strncpy

[Sharan Santhanam <sharan.santhanam@xxxxxxxxx>]

Hello Wei Chen,

Please find my comments inline.

Thanks & Regards
Sharan

On 12/13/18 10:15 AM, Wei Chen wrote:
> The strncpy needs a signed integer for 3rd parameter, but the SIZE_MAX
> is unsigned integer. We will get following error:
> /lib/nolibc/string.c:155:9: warning: ‘strncpy’: specified size
> 18446744073709551615 exceeds maximum object size 9223372036854775807
> [-Wstringop-overflow=]
>    return strncpy(dst, src, SIZE_MAX);

[1] show the posix standard function declaration strncpy using size_t[2] 
as the third parameter. The upstream code seems to be correct. I am not 
sure if we need this patch.

>           ^
> Using SSIZE_MAX to replace SIZE_MAX to fix this warning.
>
> Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
> ---
>   lib/nolibc/string.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/nolibc/string.c b/lib/nolibc/string.c
> index 6f853ba..fa450c9 100644
> --- a/lib/nolibc/string.c
> +++ b/lib/nolibc/string.c
> @@ -152,7 +152,7 @@ char *strncpy(char *dst, const char *src, size_t len)
>   
>   char *strcpy(char *dst, const char *src)
>   {
> -       return strncpy(dst, src, SIZE_MAX);
> +       return strncpy(dst, src, SSIZE_MAX);
>   }
>   
>   int strncmp(const char *str1, const char *str2, size_t len)
[1] http://pubs.opengroup.org/onlinepubs/009696899/functions/strncpy.html
[2] http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stddef.h.html

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