On 4/10/19 6:36 PM, Andrey Ignatov wrote:
> Reported in [1].
>
> With gcc 8.3.0 the following error is issued:
>
> cc -Ibpf@sta -I. -I.. -I.././include -I.././include/uapi
> -fdiagnostics-color=always -fsanitize=address,undefined
> -fno-omit-frame-pointer
> -pipe -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Werror -g -fPIC -g -O2
> -Werror -Wall -Wno-pointer-arith -Wno-sign-compare -MD -MQ
> 'bpf@sta/src_libbpf.c.o' -MF 'bpf@sta/src_libbpf.c.o.d' -o
> 'bpf@sta/src_libbpf.c.o' -c ../src/libbpf.c
> ../src/libbpf.c: In function 'bpf_object__elf_collect':
> ../src/libbpf.c:947:18: error: 'map_def_sz' may be used uninitialized in
> this
> function [-Werror=maybe-uninitialized]
> if (map_def_sz <= sizeof(struct bpf_map_def)) {
> ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ../src/libbpf.c:827:18: note: 'map_def_sz' was declared here
> int i, map_idx, map_def_sz, nr_syms, nr_maps = 0, nr_maps_glob = 0;
> ^~~~~~~~~~
>
> According to [2] -Wmaybe-uninitialized is enabled by -Wall.
> Same error is generated by clang's -Wconditional-uninitialized.
>
> [1] https://github.com/libbpf/libbpf/pull/29#issuecomment-481902601
> [2] https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
>
> Fixes: d859900c4c56 ("bpf, libbpf: support global data/bss/rodata sections")
> Reported-by: Evgeny Vereshchagin <evv...@ya.ru>
> Signed-off-by: Andrey Ignatov <r...@fb.com>
Acked-by: Yonghong Song <y...@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 e2a457e7c318..67484cf32b2e 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -824,7 +824,7 @@ bpf_object__init_internal_map(struct bpf_object *obj,
> struct bpf_map *map,
> static int
> bpf_object__init_maps(struct bpf_object *obj, int flags)
> {
> - int i, map_idx, map_def_sz, nr_syms, nr_maps = 0, nr_maps_glob = 0;
> + int i, map_idx, map_def_sz = 0, nr_syms, nr_maps = 0, nr_maps_glob = 0;
> bool strict = !(flags & MAPS_RELAX_COMPAT);
> Elf_Data *symbols = obj->efile.symbols;
> Elf_Data *data = NULL;
>
