On Thu, Jul 27, 2023 at 11:23:21AM -0700, Yonghong Song wrote:
>
>
> 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@xxxxxxxxxxxxx>
> > >
> > > 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.
nice, I think we should do the same then ;-)
bt not sure how to do the gcc check though
jirka
>
> >
> > 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@xxxxxxxxxxxxx>
> > > ---
> > > 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
> > >
> > >
> >
