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Date:   Thu, 6 Feb 2020 19:57:54 +0100
From:   Jiri Olsa <jolsa@redhat.com>
To:     Sam Lunt <samueljlunt@gmail.com>
Cc:     linux-kernel@vger.kernel.org, peterz@infradead.org,
        mingo@redhat.com, acme@kernel.org, mark.rutland@arm.com,
        alexander.shishkin@linux.intel.com, namhyung@kernel.org,
        trivial@kernel.org
Subject: Re: [PATCH] perf: Support Python 3.8+ in Makefile
Message-ID: <20200206185754.GB1669706@krava>
References: <20200131181123.tmamivhq4b7uqasr@gmail.com>
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On Fri, Jan 31, 2020 at 12:11:23PM -0600, Sam Lunt wrote:
> Python 3.8 changed the output of 'python-config --ldflags' to no longer
> include the '-lpythonX.Y' flag (this apparently fixed an issue loading
> modules with a statically linked Python executable).  The libpython
> feature check in linux/build/feature fails if the Python library is not
> included in FEATURE_CHECK_LDFLAGS-libpython variable.
> 
> This adds a check in the Makefile to determine if PYTHON_CONFIG accepts
> the '--embed' flag and passes that flag alongside '--ldflags' if so.
> 
> tools/perf is the only place the libpython feature check is used.
> 
> Signed-off-by: Sam Lunt <samuel.j.lunt@gmail.com>

Acked-by: Jiri Olsa <jolsa@redhat.com>

thanks,
jirka

> ---
>  tools/perf/Makefile.config | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index c90f4146e5a2..ccf99351f058 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -228,8 +228,17 @@ strip-libs  = $(filter-out -l%,$(1))
> 
>  PYTHON_CONFIG_SQ := $(call shell-sq,$(PYTHON_CONFIG))
> 
> +# Python 3.8 changed the output of `python-config --ldflags` to not include the
> +# '-lpythonX.Y' flag unless '--embed' is also passed. The feature check for
> +# libpython fails if that flag is not included in LDFLAGS
> +ifeq ($(shell $(PYTHON_CONFIG_SQ) --ldflags --embed 2>&1 1>/dev/null; echo $$?), 0)
> +  PYTHON_CONFIG_LDFLAGS := --ldflags --embed
> +else
> +  PYTHON_CONFIG_LDFLAGS := --ldflags
> +endif
> +
>  ifdef PYTHON_CONFIG
> -  PYTHON_EMBED_LDOPTS := $(shell $(PYTHON_CONFIG_SQ) --ldflags 2>/dev/null)
> +  PYTHON_EMBED_LDOPTS := $(shell $(PYTHON_CONFIG_SQ) $(PYTHON_CONFIG_LDFLAGS) 2>/dev/null)
>    PYTHON_EMBED_LDFLAGS := $(call strip-libs,$(PYTHON_EMBED_LDOPTS))
>    PYTHON_EMBED_LIBADD := $(call grep-libs,$(PYTHON_EMBED_LDOPTS)) -lutil
>    PYTHON_EMBED_CCOPTS := $(shell $(PYTHON_CONFIG_SQ) --includes 2>/dev/null)
> 
> base-commit: d5d359b0ac3ffc319ca93c46a4cfd87093759ad6
> -- 
> 2.25.0
>