Re: [PATCH] libbpf: Fix uninitialized warning in btf_dump_dump_type_data

[sdf@google.com]

On 11/13, David Michael wrote:
> GCC 11.3.0 fails to compile btf_dump.c due to the following error,
> which seems to originate in btf_dump_struct_data where the returned
> value would be uninitialized if btf_vlen returns zero.

> btf_dump.c: In function ‘btf_dump_dump_type_data’:
> btf_dump.c:2363:12: error: ‘err’ may be used uninitialized in this  
> function [-Werror=maybe-uninitialized]
>   2363 |         if (err < 0)
>        |            ^

> Fixes: 43174f0d4597 ("libbpf: Silence uninitialized warning/error in  
> btf_dump_dump_type_data")

Probably better to reference the original patch?
Fixes: 920d16af9b42 ("libbpf: BTF dumper support for typed data")

Acked-by: Stanislav Fomichev <sdf@google.com>

> Signed-off-by: David Michael <fedora.dm0@gmail.com>
> ---

> Hi,

> I encountered this build failure when using Gentoo's hardened profile to
> build sys-kernel/gentoo-kernel (at least some 5.19 and 6.0 versions).
> The following patch fixes it.  Can this be applied?

> Thanks.

> David

>   tools/lib/bpf/btf_dump.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

> diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
> index 12f7039e0..e9f849d82 100644
> --- a/tools/lib/bpf/btf_dump.c
> +++ b/tools/lib/bpf/btf_dump.c
> @@ -1989,7 +1989,7 @@ static int btf_dump_struct_data(struct btf_dump *d,
>   {
>   	const struct btf_member *m = btf_members(t);
>   	__u16 n = btf_vlen(t);
> -	int i, err;
> +	int i, err = 0;

>   	/* note that we increment depth before calling btf_dump_print() below;
>   	 * this is intentional.  btf_dump_data_newline() will not print a
> --
> 2.38.1