[PATCH v2] perf build: filter all combinations of -flto for libperl

[PATCH v2] perf build: filter all combinations of -flto for libperl

[Holger Hoffstätte]

When enabling 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 filtered 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@applied-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)
 
-- 
2.49.0

Re: [PATCH v2] perf build: filter all combinations of -flto for libperl

[Namhyung Kim]

On Fri, 21 Mar 2025 09:20:39 +0100, Holger Hoffstätte wrote:
> When enabling 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 filtered 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.:
> 
> [...]
Applied to perf-tools-next, thanks!

Best regards,
Namhyung