* [PATCH v2 bpf-next] libbpf: fix false uninitialized variable warning
@ 2020-04-30 2:14 Andrii Nakryiko
2020-04-30 8:13 ` Jakub Sitnicki
0 siblings, 1 reply; 3+ messages in thread
From: Andrii Nakryiko @ 2020-04-30 2:14 UTC (permalink / raw)
To: bpf, netdev, ast, daniel; +Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
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 <andriin@fb.com>
---
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;
--
2.24.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2 bpf-next] libbpf: fix false uninitialized variable warning
2020-04-30 2:14 [PATCH v2 bpf-next] libbpf: fix false uninitialized variable warning Andrii Nakryiko
@ 2020-04-30 8:13 ` Jakub Sitnicki
2020-04-30 14:25 ` Daniel Borkmann
0 siblings, 1 reply; 3+ messages in thread
From: Jakub Sitnicki @ 2020-04-30 8:13 UTC (permalink / raw)
To: Andrii Nakryiko; +Cc: bpf, netdev, ast, daniel, andrii.nakryiko, kernel-team
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 <andriin@fb.com>
> ---
> 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
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2 bpf-next] libbpf: fix false uninitialized variable warning
2020-04-30 8:13 ` Jakub Sitnicki
@ 2020-04-30 14:25 ` Daniel Borkmann
0 siblings, 0 replies; 3+ messages in thread
From: Daniel Borkmann @ 2020-04-30 14:25 UTC (permalink / raw)
To: Jakub Sitnicki, Andrii Nakryiko
Cc: bpf, netdev, ast, andrii.nakryiko, kernel-team
On 4/30/20 10:13 AM, Jakub Sitnicki wrote:
> 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 <andriin@fb.com>
>> ---
>> 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
We could do that potentially, at least to mark such locations explicitly,
although I wonder if it's not more churn than anything else adding the
infra for it. But generally no objections from my side.
Anyway, applied this one, thanks!
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-04-30 2:14 [PATCH v2 bpf-next] libbpf: fix false uninitialized variable warning Andrii Nakryiko
2020-04-30 8:13 ` Jakub Sitnicki
2020-04-30 14:25 ` Daniel Borkmann
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