From: Xiangyu Chen <[email protected]>
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:
| 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 <[email protected]>
---
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
On Thu, Jul 27, 2023 at 04:25:36PM +0800, Xiangyu Chen wrote:
> From: Xiangyu Chen <[email protected]>
>
> 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
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 <[email protected]>
> ---
> 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
>
>
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 <[email protected]>
>>
>> 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 <[email protected]>
>> ---
>> 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
>>
>>
>
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 <[email protected]>
>>
>> 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 <[email protected]>
>> ---
>> 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
>>
>>
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 <[email protected]>
> > >
> > > 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 <[email protected]>
> > > ---
> > > 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
> > >
> > >
> >