linux-kernel - Re: [PATCH v2 07/18] perf env: Remove unnecessary NULL tests

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Message-ID: <CAM9d7cjcJKjUnpYEjGap=d1fuukpsDyWCOk2_UKrepXmagceZA@mail.gmail.com>
Date:   Sun, 8 Oct 2023 23:14:12 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Yicong Yang <yangyicong@...ilicon.com>,
        Jonathan Cameron <jonathan.cameron@...wei.com>,
        Yang Jihong <yangjihong1@...wei.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Ming Wang <wangming01@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Yanteng Si <siyanteng@...ngson.cn>,
        Yuan Can <yuancan@...wei.com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        James Clark <james.clark@....com>, llvm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH v2 07/18] perf env: Remove unnecessary NULL tests

On Thu, Oct 5, 2023 at 4:09 PM Ian Rogers <irogers@...gle.com> wrote:
>
> clang-tidy was warning:
> ```
> util/env.c:334:23: warning: Access to field 'nr_pmu_mappings' results in a dereference of a null pointer (loaded from variable 'env') [clang-analyzer-core.NullDereference]
>         env->nr_pmu_mappings = pmu_num;
> ```
>
> As functions are called potentially when !env was true. This condition
> could never be true as it would produce a segv, so remove the
> unnecessary NULL tests and silence clang-tidy.

IIRC !env was to handle live sessions like perf top
or when it doesn't have a perf data file.  Anyway,
it doesn't seem to work anymore.

Thanks,
Namhyung

>
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/env.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/util/env.c b/tools/perf/util/env.c
> index a164164001fb..44140b7f596a 100644
> --- a/tools/perf/util/env.c
> +++ b/tools/perf/util/env.c
> @@ -457,7 +457,7 @@ const char *perf_env__cpuid(struct perf_env *env)
>  {
>         int status;
>
> -       if (!env || !env->cpuid) { /* Assume local operation */
> +       if (!env->cpuid) { /* Assume local operation */
>                 status = perf_env__read_cpuid(env);
>                 if (status)
>                         return NULL;
> @@ -470,7 +470,7 @@ int perf_env__nr_pmu_mappings(struct perf_env *env)
>  {
>         int status;
>
> -       if (!env || !env->nr_pmu_mappings) { /* Assume local operation */
> +       if (!env->nr_pmu_mappings) { /* Assume local operation */
>                 status = perf_env__read_pmu_mappings(env);
>                 if (status)
>                         return 0;
> @@ -483,7 +483,7 @@ const char *perf_env__pmu_mappings(struct perf_env *env)
>  {
>         int status;
>
> -       if (!env || !env->pmu_mappings) { /* Assume local operation */
> +       if (!env->pmu_mappings) { /* Assume local operation */
>                 status = perf_env__read_pmu_mappings(env);
>                 if (status)
>                         return NULL;
> --
> 2.42.0.609.gbb76f46606-goog
>