[Not a peep of feedback - if I'm doing something wrong here please let me know;
  the patch fixes a real bug someone reported in Gentoo.]

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)
  
-- 
2.48.1

Hello,

On Wed, Mar 19, 2025 at 12:10:59AM +0100, Holger Hoffstätte wrote:
> [Not a peep of feedback - if I'm doing something wrong here please let me know;
>  the patch fixes a real bug someone reported in Gentoo.]
> 
> 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>

Thanks for the fix but the patch is not applying.  Can you please check
and resend?

Thanks,
Namhyung

> ---
>  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
>