Messages in this thread | | | Subject | Re: [PATCH] net: ipv4: fix clang -Wformat warning | From | Joe Perches <> | Date | Thu, 07 Jul 2022 11:01:26 -0700 |
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On Thu, 2022-07-07 at 10:47 -0700, Justin Stitt wrote: > On Thu, Jul 7, 2022 at 10:40 AM Joe Perches <joe@perches.com> wrote: > > > > On Thu, 2022-07-07 at 10:30 -0700, Justin Stitt wrote: > > > When building with Clang we encounter this warning: > > > > net/ipv4/ah4.c:513:4: error: format specifies type 'unsigned short' but > > > > the argument has type 'int' [-Werror,-Wformat] > > > > aalg_desc->uinfo.auth.icv_fullbits / 8); > > > > > > `aalg_desc->uinfo.auth.icv_fullbits` is a u16 but due to default > > > argument promotion becomes an int. > > > > > > Variadic functions (printf-like) undergo default argument promotion. > > > Documentation/core-api/printk-formats.rst specifically recommends using > > > the promoted-to-type's format flag. > > > > > > As per C11 6.3.1.1: > > > (https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf) `If an int > > > can represent all values of the original type ..., the value is > > > converted to an int; otherwise, it is converted to an unsigned int. > > > These are called the integer promotions.` Thus it makes sense to change > > > %hu to %d not only to follow this standard but to suppress the warning > > > as well. > > > > I think it also makes sense to use %u and not %d > > as the original type is unsigned. > Yeah, that would also work. An integer (even a signed one) fully > encompasses a u16 so it's really a choice of style. Do you think the > change to %u warrants a v2 of this patch?
As it's rather odd output to use '%u != %d', probably.
Your patch, up to you.
> > > > > diff --git a/net/ipv4/ah4.c b/net/ipv4/ah4.c > > [] > > > @@ -507,7 +507,7 @@ static int ah_init_state(struct xfrm_state *x) > > > > > > if (aalg_desc->uinfo.auth.icv_fullbits/8 != > > > crypto_ahash_digestsize(ahash)) { > > > - pr_info("%s: %s digestsize %u != %hu\n", > > > + pr_info("%s: %s digestsize %u != %d\n", > > > __func__, x->aalg->alg_name, > > > crypto_ahash_digestsize(ahash), > > > aalg_desc->uinfo.auth.icv_fullbits / 8); > >
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