Messages in this thread | | | Date | Thu, 27 Jul 2023 11:23:21 -0700 | Subject | Re: [PATCH] libbpf: fix warnings "'pad_type' 'pad_bits' 'new_off' may be used uninitialized" | From | Yonghong Song <> |
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On 7/27/23 4:01 AM, Jiri Olsa wrote: > 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, > and we already have all warnings enabled: > > CFLAGS += -Werror -Wall > > they seem like false warnings also, because ARRAY_SIZE(pads) > will be always > 0
Agree. This definitely a false positive. In kernel top Makefile, we have
# Enabled with W=2, disabled by default as noisy ifdef CONFIG_CC_IS_GCC KBUILD_CFLAGS += -Wno-maybe-uninitialized endif
That means gcc -maybe-uninitialized is very noisy.
> > 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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