Messages in this thread | | | Date | Fri, 28 Jul 2023 13:39:02 +0800 | Subject | Re: [PATCH] libbpf: fix warnings "'pad_type' 'pad_bits' 'new_off' may be used uninitialized" | From | Xiangyu Chen <> |
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On 7/27/23 19:01, Jiri Olsa wrote: > CAUTION: This email comes from a non Wind River email account! > Do not click links or open attachments unless you recognize the sender and know the content is safe. > > On Thu, Jul 27, 2023 at 04:25:36PM +0800, Xiangyu Chen wrote: >> From: Xiangyu Chen <xiangyu.chen@windriver.com> >> >> When turn on the yocto DEBUG_BUILD flag, the build options for gcc would enable maybe-uninitialized, >> and following warnings would be reported as below: > curious, what's the gcc version? I can't reproduce that,
Indeed, it's also strange to me, the compiler using gcc-11.3.0 which is generated by yocto 4.2.2(mickledore branch).
The warning happens on turn on DEBUG_BUILD flag in yocto configuration, but when disable the DEBUG_BUILD flag, this
warning disappeared.
I have compared w/wo the DEBUG_BUILD's kernel build parameters this morning, when enabled the flag, the kernel build
parameters as normal, the warning won't happen. When I enabled the DEBUG_BUILD, the cflags with -Og -g -feliminate-unused-debug-types
seems the debug cflags caused the false warning behavior.
> and we already have all warnings enabled: > > CFLAGS += -Werror -Wall > > they seem like false warnings also, because ARRAY_SIZE(pads) > will be always > 0 > > jirka > >> | btf_dump.c: In function 'btf_dump_emit_bit_padding': >> | btf_dump.c:916:4: error: 'pad_type' may be used uninitialized in this function [-Werror=maybe-uninitialized] >> | 916 | btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type, >> | | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> | 917 | in_bitfield ? new_off - cur_off : 0); >> | | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> | btf_dump.c:929:6: error: 'pad_bits' may be used uninitialized in this function [-Werror=maybe-uninitialized] >> | 929 | if (bits == pad_bits) { >> | | ^ >> | btf_dump.c:913:28: error: 'new_off' may be used uninitialized in this function [-Werror=maybe-uninitialized] >> | 913 | (new_off == next_off && roundup(cur_off, next_align * 8) != new_off) || >> | | ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> | HOSTLD scripts/mod/modpost >> >> Signed-off-by: Xiangyu Chen <xiangyu.chen@windriver.com> >> --- >> tools/lib/bpf/btf_dump.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c >> index 4d9f30bf7f01..79923c3b8777 100644 >> --- a/tools/lib/bpf/btf_dump.c >> +++ b/tools/lib/bpf/btf_dump.c >> @@ -867,8 +867,8 @@ static void btf_dump_emit_bit_padding(const struct btf_dump *d, >> } pads[] = { >> {"long", d->ptr_sz * 8}, {"int", 32}, {"short", 16}, {"char", 8} >> }; >> - int new_off, pad_bits, bits, i; >> - const char *pad_type; >> + int new_off = 0, pad_bits = 0, bits, i; >> + const char *pad_type = NULL; >> >> if (cur_off >= next_off) >> return; /* no gap */ >> -- >> 2.34.1 >> >>
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