netdev - Re: [PATCH bpf-next] libbpf: Fix build with gcc-8

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Date:   Thu, 11 Apr 2019 09:45:53 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Andrey Ignatov <rdna@...com>, netdev@...r.kernel.org
Cc:     ast@...nel.org, kernel-team@...com
Subject: Re: [PATCH bpf-next] libbpf: Fix build with gcc-8

On 04/11/2019 03:36 AM, 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@.../src_libbpf.c.o' -MF 'bpf@.../src_libbpf.c.o.d' -o
>   'bpf@.../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 <evvers@...ru>
> Signed-off-by: Andrey Ignatov <rdna@...com>

Applied, thanks!