[ccan] [PATCH 1/2] opt: always initialise values in set_llong_with_suffix()

[Rusty Russell]

Douglas Bagnall <douglas at halo.gen.nz> writes:
> The helper API functions based on set_llong_with_suffix() left the
> value uninitialised in the case of an empty string argument. This is
> quite unlikely to have caused problem in practice, as most values will
> have already been set to a default and the non-NULL error message
> should have triggered an early exit or some other emergency action.
> Nevertheless, it caused a compiler warning on some minor version of
> GCC 4.8 which I no longer seem to have, and the complaint seemed
> reasonable at the time.

I'm guessing gcc being overzealous about potential uninitialized value?

I've applied it: it's no worse than the errno-after-strtoll case.

Thanks,
Rusty.

>
> If an empty string (or any other non-numeric value) is passed to
> strtoll(), the result is zero. As far as I know, the strtoll() call is
> only short-circuited here to form a more specific error message, not
> because there is a good reason for the empty string to be a special
> non-initialising case. So let's set it to zero.
>
> Signed-off-by: Douglas Bagnall <douglas at halo.gen.nz>
> ---
>  ccan/opt/helpers.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/ccan/opt/helpers.c b/ccan/opt/helpers.c
> index 747a78e..e531a7d 100644
> --- a/ccan/opt/helpers.c
> +++ b/ccan/opt/helpers.c
> @@ -238,9 +238,10 @@ static char *set_llong_with_suffix(const char *arg, long long *ll,
>  				   const long long base)
>  {
>  	char *endp;
> -	if (!arg[0])
> +	if (!arg[0]){
> +		*ll = 0;
>  		return arg_bad("'%s' (an empty string) is not a number", arg);
> -
> +	}
>  	errno = 0;
>  	*ll = strtoll(arg, &endp, 0);
>  	if (errno)
> -- 
> 1.8.3.2
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