* [PATCH bpf v1] libbpf: fix build failure from uninitialized variable warning
@ 2020-08-31 0:03 Tony Ambardar
2020-08-31 14:59 ` Daniel Borkmann
0 siblings, 1 reply; 3+ messages in thread
From: Tony Ambardar @ 2020-08-31 0:03 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann
Cc: Tony Ambardar, Andrii Nakryiko, netdev, bpf
While compiling libbpf, some GCC versions (at least 8.4.0) have difficulty
determining control flow and a emit warning for potentially uninitialized
usage of 'map', which results in a build error if using "-Werror":
In file included from libbpf.c:56:
libbpf.c: In function '__bpf_object__open':
libbpf_internal.h:59:2: warning: 'map' may be used uninitialized in this function [-Wmaybe-uninitialized]
libbpf_print(level, "libbpf: " fmt, ##__VA_ARGS__); \
^~~~~~~~~~~~
libbpf.c:5032:18: note: 'map' was declared here
struct bpf_map *map, *targ_map;
^~~
The warning/error is false based on code inspection, so silence it with a
NULL initialization.
Fixes: 646f02ffdd49 ("libbpf: Add BTF-defined map-in-map support")
Ref: 063e68813391 ("libbpf: Fix false uninitialized variable warning")
Signed-off-by: Tony Ambardar <Tony.Ambardar@gmail.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 b688aadf09c5..46d727b45c81 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -5804,8 +5804,8 @@ static int bpf_object__collect_map_relos(struct bpf_object *obj,
int i, j, nrels, new_sz;
const struct btf_var_secinfo *vi = NULL;
const struct btf_type *sec, *var, *def;
+ struct bpf_map *map = NULL, *targ_map;
const struct btf_member *member;
- struct bpf_map *map, *targ_map;
const char *name, *mname;
Elf_Data *symbols;
unsigned int moff;
--
2.25.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH bpf v1] libbpf: fix build failure from uninitialized variable warning
2020-08-31 0:03 [PATCH bpf v1] libbpf: fix build failure from uninitialized variable warning Tony Ambardar
@ 2020-08-31 14:59 ` Daniel Borkmann
2020-09-02 7:39 ` Tony Ambardar
0 siblings, 1 reply; 3+ messages in thread
From: Daniel Borkmann @ 2020-08-31 14:59 UTC (permalink / raw)
To: Tony Ambardar, Alexei Starovoitov; +Cc: Andrii Nakryiko, netdev, bpf
On 8/31/20 2:03 AM, Tony Ambardar wrote:
> While compiling libbpf, some GCC versions (at least 8.4.0) have difficulty
> determining control flow and a emit warning for potentially uninitialized
> usage of 'map', which results in a build error if using "-Werror":
>
> In file included from libbpf.c:56:
> libbpf.c: In function '__bpf_object__open':
> libbpf_internal.h:59:2: warning: 'map' may be used uninitialized in this function [-Wmaybe-uninitialized]
> libbpf_print(level, "libbpf: " fmt, ##__VA_ARGS__); \
> ^~~~~~~~~~~~
> libbpf.c:5032:18: note: 'map' was declared here
> struct bpf_map *map, *targ_map;
> ^~~
>
> The warning/error is false based on code inspection, so silence it with a
> NULL initialization.
>
> Fixes: 646f02ffdd49 ("libbpf: Add BTF-defined map-in-map support")
> Ref: 063e68813391 ("libbpf: Fix false uninitialized variable warning")
>
> Signed-off-by: Tony Ambardar <Tony.Ambardar@gmail.com>
Applied, thanks!
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH bpf v1] libbpf: fix build failure from uninitialized variable warning
2020-08-31 14:59 ` Daniel Borkmann
@ 2020-09-02 7:39 ` Tony Ambardar
0 siblings, 0 replies; 3+ messages in thread
From: Tony Ambardar @ 2020-09-02 7:39 UTC (permalink / raw)
To: Daniel Borkmann; +Cc: Alexei Starovoitov, Andrii Nakryiko, netdev, bpf
On Mon, 31 Aug 2020 at 07:59, Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On 8/31/20 2:03 AM, Tony Ambardar wrote:
> > While compiling libbpf, some GCC versions (at least 8.4.0) have difficulty
> > determining control flow and a emit warning for potentially uninitialized
> > usage of 'map', which results in a build error if using "-Werror":
> >
> > In file included from libbpf.c:56:
> > libbpf.c: In function '__bpf_object__open':
> > libbpf_internal.h:59:2: warning: 'map' may be used uninitialized in this function [-Wmaybe-uninitialized]
> > libbpf_print(level, "libbpf: " fmt, ##__VA_ARGS__); \
> > ^~~~~~~~~~~~
> > libbpf.c:5032:18: note: 'map' was declared here
> > struct bpf_map *map, *targ_map;
> > ^~~
> >
> > The warning/error is false based on code inspection, so silence it with a
> > NULL initialization.
> >
> > Fixes: 646f02ffdd49 ("libbpf: Add BTF-defined map-in-map support")
> > Ref: 063e68813391 ("libbpf: Fix false uninitialized variable warning")
> >
> > Signed-off-by: Tony Ambardar <Tony.Ambardar@gmail.com>
>
> Applied, thanks!
Thanks, Daniel. I forgot to ask/confirm whether this will get applied
to the 5.8.x stable branch, since it was first encountered there.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-08-31 0:03 [PATCH bpf v1] libbpf: fix build failure from uninitialized variable warning Tony Ambardar
2020-08-31 14:59 ` Daniel Borkmann
2020-09-02 7:39 ` Tony Ambardar
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