Re: [REGRESSION] perf build failed after 5cf6e76e4f4f ("libperf: Don't remove -g when EXTRA_CFLAGS are used") on riscv64 with gcc 13

[Ian Rogers]

On Wed, Mar 18, 2026 at 6:57 PM Haixiao Yan
<haixiao.yan.cn@xxxxxxxxxxxxx> wrote:
>
> Hi,
>
> Commit[5cf6e76e4f4f](https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/tools/lib/perf/Makefile?h=linux-6.6.y&id=5cf6e76e4f4fee54c0056758b639cf4919cffba9)
> changed the libperf Makefile to preserve external CFLAGS instead of overriding them. As a result, the -O6 optimization flags from perf's
> build system are now inherited by libperf during compilation. This triggers a false positive -Walloc-size-larger-than= warning in GCC 13 on
> riscv64, causing the build to fail with -Werror.
>
> | cpumap.c: In function 'perf_cpu_map__merge':
> | cpumap.c:422:20: error: argument 1 range [18446744065119617024, 18446744073709551612] exceeds maximum objec
> t size 9223372036854775807 [-Werror=alloc-size-larger-than=]
> |   422 |         tmp_cpus = malloc(tmp_len * sizeof(struct perf_cpu));
> |       |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> | In file included from cpumap.c:3:
> | /buildarea5/hyan-cn/project_yocto/poky/build-riscv64/tmp/work/qemuriscv64-poky-linux/perf/1.0/recipe-sysroo
> t/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__
> |       |              ^~~~~~
> | rm -f /buildarea5/hyan-cn/project_yocto/poky/build-riscv64/tmp/work/qemuriscv64-poky-linux/perf/1.0/perf-1.
> 0/libapi/libapi.a && riscv64-poky-linux-gcc-ar rcs /buildarea5/hyan-cn/project_yocto/poky/build-riscv64/tmp/w
> ork/qemuriscv64-poky-linux/perf/1.0/perf-1.0/libapi/libapi.a /buildarea5/hyan-cn/project_yocto/poky/build-ris
> cv64/tmp/work/qemuriscv64-poky-linux/perf/1.0/perf-1.0/libapi/libapi-in.o
> | cc1: all warnings being treated as errors

Hi Haixiao,

this was raised before by Chingbin in:
https://lore.kernel.org/lkml/20260212025127.841090-1-liqb365@xxxxxxx/
I was concerned about the introduction of volatile to avoid this
warning. I've mailed out what is hopefully a fix without volatile in
it:
https://lore.kernel.org/lkml/20260319081843.1650640-1-irogers@xxxxxxxxxx/
If you could take a look.

Thanks,
Ian

> Steps to reproduce:
>
> git clone -b scarthgap https://git.yoctoproject.org/poky
> cd poky
> sed -i 's/af240d7d57ebf66e87bc2dff34855e630a97ead1/5cf6e76e4f4fee54c0056758b639cf4919cffba9/' meta/recipes-kernel/linux/linux-yocto_6.6.bb
>
> source oe-init-build-env build-riscv64
>
> cat >> conf/local.conf << 'EOF'
> MACHINE = "qemuriscv64"
> 'KERNEL_VERSION_SANITY_SKIP = "1"'
> EOF
>
> bitbake perf
>
> I have confirmed that:
> Known to fail: gcc 13.3.0, 13.4.0
> Known to work: gcc 11.5.0, 12.5.0, 14.3.0, 15.2.0
>
> Not sure whether this is a gcc bug.
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124549 filed to gcc.
>
> Thanks,
> Haixiao
>
>