Merge branch 'fix-wmaybe-uninitialized-warnings-errors'

Eder Zulian says:

====================
Fix -Wmaybe-uninitialized warnings/errors

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,
====================

Link: https://lore.kernel.org/r/20241022172329.3871958-1-ezulian@redhat.com
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

3 files changed, 5 insertions, 5 deletions

diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index d54aaa0619df9..bd9f960bce3d5 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;
 
diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index 8440c2c5ad3ed..468392f9882d2 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 */
diff --git a/tools/lib/subcmd/parse-options.c b/tools/lib/subcmd/parse-options.c
index eb896d30545b6..555d617c1f502 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 */