Subject: Re: [PATCH v2 bpf-next] libbpf: fix false uninitialized variable warning

From: Jakub Sitnicki <[email-masked]>
Date: Thu, 30 Apr 2020 10:13:28 +0200

On Thu, Apr 30, 2020 at 04:14 AM CEST, Andrii Nakryiko wrote:
> Some versions of GCC falsely detect that vi might not be initialized. That's
> not true, but let's silence it with NULL initialization.
>
> Signed-off-by: Andrii Nakryiko <[email-masked]>
> ---
>  tools/lib/bpf/libbpf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index d86ff8214b96..977add1b73e2 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -5003,8 +5003,8 @@ static int bpf_object__collect_map_relos(struct bpf_object *obj,
>  					 GElf_Shdr *shdr, Elf_Data *data)
>  {
>  	int i, j, nrels, new_sz, ptr_sz = sizeof(void *);
> +	const struct btf_var_secinfo *vi = NULL;
>  	const struct btf_type *sec, *var, *def;
> -	const struct btf_var_secinfo *vi;
>  	const struct btf_member *member;
>  	struct bpf_map *map, *targ_map;
>  	const char *name, *mname;

Alternatively we could borrow the kernel uninitialized_var macro:

include/linux/compiler-clang.h:#define uninitialized_var(x) x = *(&(x))
include/linux/compiler-gcc.h:#define uninitialized_var(x) x = x