[PATCH] tools/lib/perf: Fix -Werror=alloc-size-larger-than in cpumap.c

[Mukesh Kumar Chaurasiya]

On Sun, Apr 06, 2025 at 10:04:12PM +0530, Likhitha Korrapati wrote:
> perf build break observed when using gcc 13-3 (FC39 ppc64le)
> with the following error.
> 
> cpumap.c: In function 'perf_cpu_map__merge':
> cpumap.c:414:20: error: argument 1 range [18446744069414584320, 18446744073709551614] exceeds maximum object size 9223372036854775807 [-Werror=alloc-size-larger-than=]
>   414 |         tmp_cpus = malloc(tmp_len * sizeof(struct perf_cpu));
>       |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> In file included from cpumap.c:4:
> /usr/include/stdlib.h:672:14: note: in a call to allocation function 'malloc' declared here
>   672 | extern void *malloc (size_t __size) __THROW __attribute_malloc__
>       |              ^~~~~~
> cc1: all warnings being treated as errors
> 
> Error happens to be only in gcc13-3 and not in latest gcc 14.
> Even though git-bisect pointed bad commit as:
> 'commit f5b07010c13c ("libperf: Don't remove -g when EXTRA_CFLAGS are used")',
> issue is with tmp_len being "int". It holds number of cpus and making
> it "unsigned int" fixes the issues.
> 
> After the fix:
> 
>   CC      util/pmu-flex.o
>   CC      util/expr-flex.o
>   LD      util/perf-util-in.o
>   LD      perf-util-in.o
>   AR      libperf-util.a
>   LINK    perf
>   GEN     python/perf.cpython-312-powerpc64le-linux-gnu.so
> 
> Signed-off-by: Likhitha Korrapati <likhitha at linux.ibm.com>
> ---
>  tools/lib/perf/cpumap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c
> index 4454a5987570..c7c784e18225 100644
> --- a/tools/lib/perf/cpumap.c
> +++ b/tools/lib/perf/cpumap.c
> @@ -398,7 +398,7 @@ bool perf_cpu_map__is_subset(const struct perf_cpu_map *a, const struct perf_cpu
>  int perf_cpu_map__merge(struct perf_cpu_map **orig, struct perf_cpu_map *other)
>  {
>  	struct perf_cpu *tmp_cpus;
> -	int tmp_len;
> +	unsigned int tmp_len;
>  	int i, j, k;
>  	struct perf_cpu_map *merged;
>
LGTM

Reviewed-by: Mukesh Kumar Chaurasiya <mchauras at linux.ibm.com>

> -- 
> 2.43.5
>