linux-kernel - Re: [PATCH] perf: Always feature test reallocarray

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Message-ID: <CAP-5=fUS4P6dFXXQ23pvv8+yP6XDt4YmL+NqnGu-+i1EmjmOkA@mail.gmail.com>
Date: Wed, 29 Jan 2025 15:39:13 -0800
From: Ian Rogers <irogers@...gle.com>
To: James Clark <james.clark@...aro.org>
Cc: linux-perf-users@...r.kernel.org, Ali Utku Selen <ali.utku.selen@....com>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...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>, "Liang, Kan" <kan.liang@...ux.intel.com>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: Always feature test reallocarray

On Wed, Jan 29, 2025 at 7:44 AM James Clark <james.clark@...aro.org> wrote:
>
> This is also used in util/comm.c now, so instead of selectively doing
> the feature test, always do it. If it's ever used anywhere else it's
> less likely to cause another build failure.
>
> This doesn't remove the need to manually include libc_compat.h, and
> missing that will still cause an error for glibc < 2.26. There isn't a
> way to fix that without poisoning reallocarray like libbpf did, but that
> has other downsides like making memory debugging tools less useful. So
> for Perf keep it like this and we'll have to fix up any missed includes.
>
> Fixes the following build error:
>
>   util/comm.c:152:31: error: implicit declaration of function
>                       'reallocarray' [-Wimplicit-function-declaration]
>   152 |                         tmp = reallocarray(comm_strs->strs,
>       |                               ^~~~~~~~~~~~
>
> Fixes: 13ca628716c6 ("perf comm: Add reference count checking to 'struct comm_str'")
> Reported-by: Ali Utku Selen <ali.utku.selen@....com>
> Signed-off-by: James Clark <james.clark@...aro.org>

Reviewed-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> ---
>  tools/perf/Makefile.config | 10 ++++------
>  tools/perf/util/comm.c     |  2 ++
>  2 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index a148ca9efca9..ed3ba13f1018 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -497,13 +497,14 @@ ifeq ($(feature-setns), 1)
>    $(call detected,CONFIG_SETNS)
>  endif
>
> +ifeq ($(feature-reallocarray), 0)
> +      CFLAGS += -DCOMPAT_NEED_REALLOCARRAY
> +endif
> +
>  ifdef CORESIGHT
>    $(call feature_check,libopencsd)
>    ifeq ($(feature-libopencsd), 1)
>      CFLAGS += -DHAVE_CSTRACE_SUPPORT $(LIBOPENCSD_CFLAGS)
> -    ifeq ($(feature-reallocarray), 0)
> -      CFLAGS += -DCOMPAT_NEED_REALLOCARRAY
> -    endif
>      LDFLAGS += $(LIBOPENCSD_LDFLAGS)
>      EXTLIBS += $(OPENCSDLIBS)
>      $(call detected,CONFIG_LIBOPENCSD)
> @@ -1103,9 +1104,6 @@ ifndef NO_AUXTRACE
>    ifndef NO_AUXTRACE
>      $(call detected,CONFIG_AUXTRACE)
>      CFLAGS += -DHAVE_AUXTRACE_SUPPORT
> -    ifeq ($(feature-reallocarray), 0)
> -      CFLAGS += -DCOMPAT_NEED_REALLOCARRAY
> -    endif
>    endif
>  endif
>
> diff --git a/tools/perf/util/comm.c b/tools/perf/util/comm.c
> index 49b79cf0c5cc..8aa456d7c2cd 100644
> --- a/tools/perf/util/comm.c
> +++ b/tools/perf/util/comm.c
> @@ -5,6 +5,8 @@
>  #include <internal/rc_check.h>
>  #include <linux/refcount.h>
>  #include <linux/zalloc.h>
> +#include <tools/libc_compat.h> // reallocarray
> +
>  #include "rwsem.h"
>
>  DECLARE_RC_STRUCT(comm_str) {
> --
> 2.34.1
>