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libbpf: Fix build with gcc-8 

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: d859900c4c ("bpf, libbpf: support global data/bss/rodata sections")
Reported-by: Evgeny Vereshchagin <evvers@ya.ru>
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Andrey Ignatov 2019-04-10 18:36:43 -07:00 committed by Daniel Borkmann
parent fa0dcb3fe2
commit d5adbdd77e
1 changed files with 1 additions and 1 deletions
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2
tools/lib/bpf/libbpf.c
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@ -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;