linux-kernel - [PATCH] perf build: filter all combinations of -flto for libbperl

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Message-ID: <fa1c3b38-6a23-af22-0e5e-280fa523d06a@applied-asynchrony.com>
Date: Tue, 11 Mar 2025 18:33:09 +0100
From: Holger Hoffstätte <holger@...lied-asynchrony.com>
To: linux-perf-users@...r.kernel.org,
 linux-kernel <linux-kernel@...r.kernel.org>,
 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>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 "Liang, Kan" <kan.liang@...ux.intel.com>
Cc: Guilherme Amadio <amadio@...too.org>
Subject: [PATCH] perf build: filter all combinations of -flto for libbperl

When building the libperl feature the build uses perl's build flags
(ccopts) but filters out various flags, e.g. for LTO.
While this is conceptually correct, it is insufficient in practice,
since only "-flto=auto" is filterd out. When perl itself is built with
"-flto" this can cause parts of perf being built with LTO and others
without, giving exciting build errors like e.g.:

   ../tools/perf/pmu-events/pmu-events.c:72851:(.text+0xb79): undefined
   reference to `strcmp_cpuid_str' collect2: error: ld returned 1 exit status

Fix this by filtering all matching flag values of -flto{=n,auto,..}.

Signed-off-by: Holger Hoffstätte <holger@...lied-asynchrony.com>
---
  tools/perf/Makefile.config | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index a148ca9ef..4f5a40ab8 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -820,7 +820,7 @@ else
    PERL_EMBED_LIBADD = $(call grep-libs,$(PERL_EMBED_LDOPTS))
    PERL_EMBED_CCOPTS = $(shell perl -MExtUtils::Embed -e ccopts 2>/dev/null)
    PERL_EMBED_CCOPTS := $(filter-out -specs=%,$(PERL_EMBED_CCOPTS))
-  PERL_EMBED_CCOPTS := $(filter-out -flto=auto -ffat-lto-objects, $(PERL_EMBED_CCOPTS))
+  PERL_EMBED_CCOPTS := $(filter-out -flto% -ffat-lto-objects, $(PERL_EMBED_CCOPTS))
    PERL_EMBED_LDOPTS := $(filter-out -specs=%,$(PERL_EMBED_LDOPTS))
    FLAGS_PERL_EMBED=$(PERL_EMBED_CCOPTS) $(PERL_EMBED_LDOPTS)
  
-- 
2.48.1