Re: [PATCH] tools/resolve_btfids: Fix 'variable' may be used uninitialized warnings

[Yonghong Song]

On 10/11/24 1:00 PM, Eder Zulian wrote:
> - tools/bpf/resolve_btfids/main.c: Initialize 'set' and 'set8' pointers
>    to NULL in to fix compiler warnings.
>
> - tools/lib/bpf/btf_dump.c: Initialize 'new_off' and 'pad_bits' to 0 and
>    'pad_type' to  NULL to prevent compiler warnings.
>
> - tools/lib/subcmd/parse-options.c: Initiazlide pointer 'o' to NULL
>    avoiding a compiler warning.
>
> Tested on x86_64 with clang version 17.0.6 and gcc (GCC) 13.3.1.
>
> $ cd tools/bpf/resolve_btfids
> $ for c in gcc clang; do \
> for o in fast g s z $(seq 0 3); do \
> make clean && \
> make HOST_CC=${c} "HOSTCFLAGS=-O${o} -Wall" 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 not observed after applying this
> patch.
>
> Signed-off-by: Eder Zulian <ezulian@xxxxxxxxxx>

Currently compilation is okay although it uses -O0.

One choice is to move from -O0 to -O2 and fix corresponding -Wmaybe-uninitialized issues.
Otherwise, since there is no bug, not sure whether we should make changes or not.
Maintainers can decide the next step.