[PATCH v2 0/3] Fix -Wmaybe-uninitialized warnings/errors

[PATCH v2 0/3] Fix -Wmaybe-uninitialized warnings/errors

[Eder Zulian]

Hello!

This v2 series initializes the variables 'set' and 'set8' in sets_patch to
NULL, along with the variables 'new_off' and 'pad_bits' and 'pad_type' in
btf_dump_emit_bit_padding to zero or NULL according to their types and the
variable 'o' in options__order to NULL to prevent compiler warnings/errors
which are observed when compiling with non-default compilation options, but
are not emitted by the compiler with the current default compilation
options.

- tools/bpf/resolve_btfids/main.c: Initialize the variables 'set' and
  'set8' in sets_patch to NULL.

- tools/lib/bpf/btf_dump.c: Initialize the variables 'new_off' and
  'pad_bits' and 'pad_type' in btf_dump_emit_bit_padding to zero/NULL

- tools/lib/subcmd/parse-options.c: Initialize the variable 'o' in
  options__order to NULL.
  Sam James mentioned that Michael Weiß had previously sent an alternative
  patch as
  https://lore.kernel.org/all/20240731085217.94928-1-michael.weiss@aisec.fraunhofer.de/

Tested on x86_64 with clang version 17.0.6 and gcc (GCC) 13.3.1.

  $ for c in gcc clang; do for o in fast g s z $(seq 0 3); do make -C \
  tools/bpf/resolve_btfids/ HOST_CC=${c} "HOSTCFLAGS=-O${o} -Wall" \
  clean all 2>&1 | tee ${c}-O${o}.out; done; done && \
  grep 'warning:\|error:' *.out

  [...]
  clang-O1.out:main.c:163:9: warning: ‘set8’ may be used uninitialized [-Wmaybe-uninitialized]
  clang-O1.out:main.c:163:9: warning: ‘set’ may be used uninitialized [-Wmaybe-uninitialized]
  clang-O2.out:main.c:163:9: warning: ‘set8’ may be used uninitialized [-Wmaybe-uninitialized]
  clang-O2.out:main.c:163:9: warning: ‘set’ may be used uninitialized [-Wmaybe-uninitialized]
  clang-O3.out:main.c:163:9: warning: ‘set8’ may be used uninitialized [-Wmaybe-uninitialized]
  clang-O3.out:main.c:163:9: warning: ‘set’ may be used uninitialized [-Wmaybe-uninitialized]
  clang-Ofast.out:main.c:163:9: warning: ‘set8’ may be used uninitialized [-Wmaybe-uninitialized]
  clang-Ofast.out:main.c:163:9: warning: ‘set’ may be used uninitialized [-Wmaybe-uninitialized]
  clang-Og.out:btf_dump.c:903:42: error: ‘new_off’ may be used uninitialized [-Werror=maybe-uninitialized]
  clang-Og.out:btf_dump.c:917:25: error: ‘pad_type’ may be used uninitialized [-Werror=maybe-uninitialized]
  clang-Og.out:btf_dump.c:930:20: error: ‘pad_bits’ may be used uninitialized [-Werror=maybe-uninitialized]
  clang-Os.out:parse-options.c:832:9: error: ‘o’ may be used uninitialized [-Werror=maybe-uninitialized]
  clang-Oz.out:parse-options.c:832:9: error: ‘o’ may be used uninitialized [-Werror=maybe-uninitialized]
  gcc-O1.out:main.c:163:9: warning: ‘set8’ may be used uninitialized [-Wmaybe-uninitialized]
  gcc-O1.out:main.c:163:9: warning: ‘set’ may be used uninitialized [-Wmaybe-uninitialized]
  gcc-O2.out:main.c:163:9: warning: ‘set8’ may be used uninitialized [-Wmaybe-uninitialized]
  gcc-O2.out:main.c:163:9: warning: ‘set’ may be used uninitialized [-Wmaybe-uninitialized]
  gcc-O3.out:main.c:163:9: warning: ‘set8’ may be used uninitialized [-Wmaybe-uninitialized]
  gcc-O3.out:main.c:163:9: warning: ‘set’ may be used uninitialized [-Wmaybe-uninitialized]
  gcc-Ofast.out:main.c:163:9: warning: ‘set8’ may be used uninitialized [-Wmaybe-uninitialized]
  gcc-Ofast.out:main.c:163:9: warning: ‘set’ may be used uninitialized [-Wmaybe-uninitialized]
  gcc-Og.out:btf_dump.c:903:42: error: ‘new_off’ may be used uninitialized [-Werror=maybe-uninitialized]
  gcc-Og.out:btf_dump.c:917:25: error: ‘pad_type’ may be used uninitialized [-Werror=maybe-uninitialized]
  gcc-Og.out:btf_dump.c:930:20: error: ‘pad_bits’ may be used uninitialized [-Werror=maybe-uninitialized]
  gcc-Os.out:parse-options.c:832:9: error: ‘o’ may be used uninitialized [-Werror=maybe-uninitialized]
  gcc-Oz.out:parse-options.c:832:9: error: ‘o’ may be used uninitialized [-Werror=maybe-uninitialized]

The above warnings and/or errors are fixed. However, they are observed with
current default compilation options.

Updates since v1:

- Incorporate feedback from reviewers. Add a comment about an alternative
  patch for parse-options.c sent before (based on comments from Sam James.)
  Split in multiple patches creating this series and a typo was fixed
  "Initiazlide" -> "Initialize" (suggested by Viktor Malik). State more
  clearly that the -Wmaybe-uninitialized issues only happen when compiling
  with non-default compilation options (based on comments from Yonghong
  Song.)

Thanks,

Eder Zulian (3):
  resolve_btfids: Fix compiler warnings
  libbpf: Prevent compiler warnings/errors
  libsubcmd: Silence compiler warning

 tools/bpf/resolve_btfids/main.c  | 4 ++--
 tools/lib/bpf/btf_dump.c         | 4 ++--
 tools/lib/subcmd/parse-options.c | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

-- 
2.46.2

[PATCH v2 1/3] resolve_btfids: Fix compiler warnings

[Eder Zulian]

Initialize 'set' and 'set8' pointers to NULL in sets_patch to prevent
possible compiler warnings which are issued for various optimization
levels, but do not happen when compiling with current default
compilation options.

For example, when compiling resolve_btfids with

  $ make "HOSTCFLAGS=-O2 -Wall" -C tools/bpf/resolve_btfids/ clean all

Clang version 17.0.6 and GCC 13.3.1 issue following
-Wmaybe-uninitialized warnings for variables 'set8' and 'set':

  In function ‘sets_patch’,
      inlined from ‘symbols_patch’ at main.c:748:6,
      inlined from ‘main’ at main.c:823:6:
  main.c:163:9: warning: ‘set8’ may be used uninitialized [-Wmaybe-uninitialized]
    163 |         eprintf(1, verbose, pr_fmt(fmt), ##__VA_ARGS__)
        |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  main.c:729:17: note: in expansion of macro ‘pr_debug’
    729 |                 pr_debug("sorting  addr %5lu: cnt %6d [%s]\n",
        |                 ^~~~~~~~
  main.c: In function ‘main’:
  main.c:682:37: note: ‘set8’ was declared here
    682 |                 struct btf_id_set8 *set8;
        |                                     ^~~~
  In function ‘sets_patch’,
      inlined from ‘symbols_patch’ at main.c:748:6,
      inlined from ‘main’ at main.c:823:6:
  main.c:163:9: warning: ‘set’ may be used uninitialized [-Wmaybe-uninitialized]
    163 |         eprintf(1, verbose, pr_fmt(fmt), ##__VA_ARGS__)
        |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  main.c:729:17: note: in expansion of macro ‘pr_debug’
    729 |                 pr_debug("sorting  addr %5lu: cnt %6d [%s]\n",
        |                 ^~~~~~~~
  main.c: In function ‘main’:
  main.c:683:36: note: ‘set’ was declared here
    683 |                 struct btf_id_set *set;
        |                                    ^~~

Signed-off-by: Eder Zulian <ezulian@redhat.com>
---
 tools/bpf/resolve_btfids/main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index d54aaa0619df..bd9f960bce3d 100644
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -679,8 +679,8 @@ static int sets_patch(struct object *obj)
 
 	next = rb_first(&obj->sets);
 	while (next) {
-		struct btf_id_set8 *set8;
-		struct btf_id_set *set;
+		struct btf_id_set8 *set8 = NULL;
+		struct btf_id_set *set = NULL;
 		unsigned long addr, off;
 		struct btf_id *id;
 
-- 
2.46.2

[PATCH v2 2/3] libbpf: Prevent compiler warnings/errors

[Eder Zulian]

Initialize 'new_off' and 'pad_bits' to 0 and 'pad_type' to  NULL in
btf_dump_emit_bit_padding to prevent compiler warnings/errors which are
observed when compiling with 'EXTRA_CFLAGS=-g -Og' options, but do not
happen when compiling with current default options.

For example, when compiling libbpf with

  $ make "EXTRA_CFLAGS=-g -Og" -C tools/lib/bpf/ clean all

Clang version 17.0.6 and GCC 13.3.1 fail to compile btf_dump.c due to
following errors:

  btf_dump.c: In function ‘btf_dump_emit_bit_padding’:
  btf_dump.c:903:42: error: ‘new_off’ may be used uninitialized [-Werror=maybe-uninitialized]
    903 |         if (new_off > cur_off && new_off <= next_off) {
        |                                  ~~~~~~~~^~~~~~~~~~~
  btf_dump.c:870:13: note: ‘new_off’ was declared here
    870 |         int new_off, pad_bits, bits, i;
        |             ^~~~~~~
  btf_dump.c:917:25: error: ‘pad_type’ may be used uninitialized [-Werror=maybe-uninitialized]
    917 |                         btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type,
        |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    918 |                                         in_bitfield ? new_off - cur_off : 0);
        |                                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  btf_dump.c:871:21: note: ‘pad_type’ was declared here
    871 |         const char *pad_type;
        |                     ^~~~~~~~
  btf_dump.c:930:20: error: ‘pad_bits’ may be used uninitialized [-Werror=maybe-uninitialized]
    930 |                 if (bits == pad_bits) {
        |                    ^
  btf_dump.c:870:22: note: ‘pad_bits’ was declared here
    870 |         int new_off, pad_bits, bits, i;
        |                      ^~~~~~~~
  cc1: all warnings being treated as errors

Signed-off-by: Eder Zulian <ezulian@redhat.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 8440c2c5ad3e..468392f9882d 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 */
-- 
2.46.2

[PATCH v2 3/3] libsubcmd: Silence compiler warning

[Eder Zulian]

Initialize the pointer 'o' in options__order to NULL to prevent a
compiler warning/error which is observed when compiling with the '-Og'
option, but is not emitted by the compiler with the current default
compilation options.

For example, when compiling libsubcmd with

 $ make "EXTRA_CFLAGS=-Og" -C tools/lib/subcmd/ clean all

Clang version 17.0.6 and GCC 13.3.1 fail to compile parse-options.c due
to following error:

  parse-options.c: In function ‘options__order’:
  parse-options.c:832:9: error: ‘o’ may be used uninitialized [-Werror=maybe-uninitialized]
    832 |         memcpy(&ordered[nr_opts], o, sizeof(*o));
        |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  parse-options.c:810:30: note: ‘o’ was declared here
    810 |         const struct option *o, *p = opts;
        |                              ^
  cc1: all warnings being treated as errors

Signed-off-by: Eder Zulian <ezulian@redhat.com>
---
 tools/lib/subcmd/parse-options.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/subcmd/parse-options.c b/tools/lib/subcmd/parse-options.c
index eb896d30545b..555d617c1f50 100644
--- a/tools/lib/subcmd/parse-options.c
+++ b/tools/lib/subcmd/parse-options.c
@@ -807,7 +807,7 @@ static int option__cmp(const void *va, const void *vb)
 static struct option *options__order(const struct option *opts)
 {
 	int nr_opts = 0, nr_group = 0, nr_parent = 0, len;
-	const struct option *o, *p = opts;
+	const struct option *o = NULL, *p = opts;
 	struct option *opt, *ordered = NULL, *group;
 
 	/* flatten the options that have parents */
-- 
2.46.2

Re: [PATCH v2 3/3] libsubcmd: Silence compiler warning

[Andrii Nakryiko]

On Tue, Oct 22, 2024 at 10:24 AM Eder Zulian <ezulian@redhat.com> wrote:
>
> Initialize the pointer 'o' in options__order to NULL to prevent a
> compiler warning/error which is observed when compiling with the '-Og'
> option, but is not emitted by the compiler with the current default
> compilation options.
>
> For example, when compiling libsubcmd with
>
>  $ make "EXTRA_CFLAGS=-Og" -C tools/lib/subcmd/ clean all
>
> Clang version 17.0.6 and GCC 13.3.1 fail to compile parse-options.c due
> to following error:
>
>   parse-options.c: In function ‘options__order’:
>   parse-options.c:832:9: error: ‘o’ may be used uninitialized [-Werror=maybe-uninitialized]
>     832 |         memcpy(&ordered[nr_opts], o, sizeof(*o));
>         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   parse-options.c:810:30: note: ‘o’ was declared here
>     810 |         const struct option *o, *p = opts;
>         |                              ^
>   cc1: all warnings being treated as errors
>
> Signed-off-by: Eder Zulian <ezulian@redhat.com>
> ---
>  tools/lib/subcmd/parse-options.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>

First two patches look good, we can take them through bpf-next. What
do we do with this one? Arnaldo, would you like us to take it through
bpf-next as well (if yes, please give your ack), or you'd like to take
it through your tree?

> diff --git a/tools/lib/subcmd/parse-options.c b/tools/lib/subcmd/parse-options.c
> index eb896d30545b..555d617c1f50 100644
> --- a/tools/lib/subcmd/parse-options.c
> +++ b/tools/lib/subcmd/parse-options.c
> @@ -807,7 +807,7 @@ static int option__cmp(const void *va, const void *vb)
>  static struct option *options__order(const struct option *opts)
>  {
>         int nr_opts = 0, nr_group = 0, nr_parent = 0, len;
> -       const struct option *o, *p = opts;
> +       const struct option *o = NULL, *p = opts;
>         struct option *opt, *ordered = NULL, *group;
>
>         /* flatten the options that have parents */
> --
> 2.46.2
>

Re: [PATCH v2 0/3] Fix -Wmaybe-uninitialized warnings/errors

[Jiri Olsa]

On Tue, Oct 22, 2024 at 07:23:26PM +0200, Eder Zulian wrote:

SNIP

> The above warnings and/or errors are fixed. However, they are observed with
> current default compilation options.
> 
> Updates since v1:
> 
> - Incorporate feedback from reviewers. Add a comment about an alternative
>   patch for parse-options.c sent before (based on comments from Sam James.)
>   Split in multiple patches creating this series and a typo was fixed
>   "Initiazlide" -> "Initialize" (suggested by Viktor Malik). State more
>   clearly that the -Wmaybe-uninitialized issues only happen when compiling
>   with non-default compilation options (based on comments from Yonghong
>   Song.)
> 
> Thanks,
> 
> Eder Zulian (3):
>   resolve_btfids: Fix compiler warnings
>   libbpf: Prevent compiler warnings/errors
>   libsubcmd: Silence compiler warning

Acked-by: Jiri Olsa <jolsa@kernel.org>

jirka

> 
>  tools/bpf/resolve_btfids/main.c  | 4 ++--
>  tools/lib/bpf/btf_dump.c         | 4 ++--
>  tools/lib/subcmd/parse-options.c | 2 +-
>  3 files changed, 5 insertions(+), 5 deletions(-)
> 
> -- 
> 2.46.2
> 

Re: [PATCH v2 3/3] libsubcmd: Silence compiler warning

[Arnaldo Carvalho de Melo]

On Tue, Oct 22, 2024 at 04:18:15PM -0700, Andrii Nakryiko wrote:
> On Tue, Oct 22, 2024 at 10:24 AM Eder Zulian <ezulian@redhat.com> wrote:
> >
> > Initialize the pointer 'o' in options__order to NULL to prevent a
> > compiler warning/error which is observed when compiling with the '-Og'
> > option, but is not emitted by the compiler with the current default
> > compilation options.
> >
> > For example, when compiling libsubcmd with
> >
> >  $ make "EXTRA_CFLAGS=-Og" -C tools/lib/subcmd/ clean all
> >
> > Clang version 17.0.6 and GCC 13.3.1 fail to compile parse-options.c due
> > to following error:
> >
> >   parse-options.c: In function ‘options__order’:
> >   parse-options.c:832:9: error: ‘o’ may be used uninitialized [-Werror=maybe-uninitialized]
> >     832 |         memcpy(&ordered[nr_opts], o, sizeof(*o));
> >         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >   parse-options.c:810:30: note: ‘o’ was declared here
> >     810 |         const struct option *o, *p = opts;
> >         |                              ^
> >   cc1: all warnings being treated as errors
> >
> > Signed-off-by: Eder Zulian <ezulian@redhat.com>
> > ---
> >  tools/lib/subcmd/parse-options.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> 
> First two patches look good, we can take them through bpf-next. What
> do we do with this one? Arnaldo, would you like us to take it through
> bpf-next as well (if yes, please give your ack), or you'd like to take

Yes, please take it thru bpf-next

Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>

- Arnaldo

> it through your tree?
 
> > diff --git a/tools/lib/subcmd/parse-options.c b/tools/lib/subcmd/parse-options.c
> > index eb896d30545b..555d617c1f50 100644
> > --- a/tools/lib/subcmd/parse-options.c
> > +++ b/tools/lib/subcmd/parse-options.c
> > @@ -807,7 +807,7 @@ static int option__cmp(const void *va, const void *vb)
> >  static struct option *options__order(const struct option *opts)
> >  {
> >         int nr_opts = 0, nr_group = 0, nr_parent = 0, len;
> > -       const struct option *o, *p = opts;
> > +       const struct option *o = NULL, *p = opts;
> >         struct option *opt, *ordered = NULL, *group;
> >
> >         /* flatten the options that have parents */
> > --
> > 2.46.2

Re: [PATCH v2 0/3] Fix -Wmaybe-uninitialized warnings/errors

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Tue, 22 Oct 2024 19:23:26 +0200 you wrote:
> Hello!
> 
> This v2 series initializes the variables 'set' and 'set8' in sets_patch to
> NULL, along with the variables 'new_off' and 'pad_bits' and 'pad_type' in
> btf_dump_emit_bit_padding to zero or NULL according to their types and the
> variable 'o' in options__order to NULL to prevent compiler warnings/errors
> which are observed when compiling with non-default compilation options, but
> are not emitted by the compiler with the current default compilation
> options.
> 
> [...]

Here is the summary with links:
  - [v2,1/3] resolve_btfids: Fix compiler warnings
    https://git.kernel.org/bpf/bpf-next/c/2c3d022abe6c
  - [v2,2/3] libbpf: Prevent compiler warnings/errors
    https://git.kernel.org/bpf/bpf-next/c/7f4ec77f3fee
  - [v2,3/3] libsubcmd: Silence compiler warning
    https://git.kernel.org/bpf/bpf-next/c/7a4ffec9fd54

You are awesome, thank you!
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