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

From: Namhyung Kim <namhyung@kernel.org>
To: Ian Rogers <irogers@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	 Tom Rix <trix@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	 Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	 Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@kernel.org>,
	 Adrian Hunter <adrian.hunter@intel.com>,
	Yicong Yang <yangyicong@hisilicon.com>,
	 Jonathan Cameron <jonathan.cameron@huawei.com>,
	Yang Jihong <yangjihong1@huawei.com>,
	 Kan Liang <kan.liang@linux.intel.com>,
	Ming Wang <wangming01@loongson.cn>,
	 Huacai Chen <chenhuacai@kernel.org>,
	Sean Christopherson <seanjc@google.com>,
	 K Prateek Nayak <kprateek.nayak@amd.com>,
	Yanteng Si <siyanteng@loongson.cn>,
	 Yuan Can <yuancan@huawei.com>,
	Ravi Bangoria <ravi.bangoria@amd.com>,
	 James Clark <james.clark@arm.com>,
	llvm@lists.linux.dev, linux-kernel@vger.kernel.org,
	 linux-perf-users@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH v2 07/18] perf env: Remove unnecessary NULL tests
Date: Sun, 8 Oct 2023 23:14:12 -0700	[thread overview]
Message-ID: <CAM9d7cjcJKjUnpYEjGap=d1fuukpsDyWCOk2_UKrepXmagceZA@mail.gmail.com> (raw)
In-Reply-To: <20231005230851.3666908-8-irogers@google.com>

On Thu, Oct 5, 2023 at 4:09 PM Ian Rogers <irogers@google.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@google.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
>