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>