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Date: Wed, 8 Jul 2026 17:12:42 -0700
From: Namhyung Kim <namhyung@kernel.org>
To: Trevor Allison <tallison@redhat.com>
Cc: peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
	mark.rutland@arm.com, alexander.shishkin@linux.intel.com,
	jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com,
	james.clark@linaro.org, linux-perf-users@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] perf build: Fix LTO build of libperf-jvmti.so
Message-ID: <ak7neuxFS3ZuGL4F@google.com>
References: <20260701042145.71595-1-tallison@redhat.com>
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In-Reply-To: <20260701042145.71595-1-tallison@redhat.com>

Hello,

On Wed, Jul 01, 2026 at 12:21:45AM -0400, Trevor Allison wrote:
> Linking libperf-jvmti.so through jvmti-in.o (ld -r) breaks LTO when
> -flto is passed via LDFLAGS.  Link the JVMTI object files directly
> instead, and pass any LTO flags from LDFLAGS to the JVMTI compile step

Can you share the error message and put it in the commit message?

I think my build is fine with LDFLAGS=-flto.

Thanks,
Namhyung

> 
> Signed-off-by: Trevor Allison <tallison@redhat.com>
> ---
>  tools/perf/Makefile.perf | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index 3f0544d37a7f..bc66d711fa39 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -686,10 +686,12 @@ ifndef NO_JVMTI
>  LIBJVMTI_IN := $(OUTPUT)jvmti/jvmti-in.o
>  
>  $(LIBJVMTI_IN): prepare FORCE
> -	$(Q)$(MAKE) -f $(srctree)/tools/build/Makefile.build dir=jvmti obj=jvmti
> +	$(Q)$(MAKE) -f $(srctree)/tools/build/Makefile.build dir=jvmti obj=jvmti \
> +		CFLAGS="$(CFLAGS) $(filter -flto% -ffat-lto-objects,$(LDFLAGS))"
>  
>  $(OUTPUT)$(LIBJVMTI): $(LIBJVMTI_IN)
> -	$(QUIET_LINK)$(CC) $(LDFLAGS) -shared -Wl,-soname -Wl,$(LIBJVMTI) -o $@ $<
> +	$(QUIET_LINK)$(CC) $(LDFLAGS) -shared -Wl,-soname -Wl,$(LIBJVMTI) -o $@ \
> +		$(addprefix $(OUTPUT)jvmti/,libjvmti.o jvmti_agent.o libstring.o libctype.o)
>  endif
>  
>  $(patsubst perf-%,%.o,$(PROGRAMS)): $(wildcard */*.h)
> -- 
> 2.50.1 (Apple Git-155)
>