Re: [PATCH 1/1] perf tools: Use Python devtools for version autodetection rather than runtime

[German Gomez <german.gomez@arm.com>]

Hi James,

On 09/03/2022 19:43, James Clark wrote:
> This fixes the issue where the build will fail if only the Python2
> runtime is installed but the Python3 devtools are installed. Currently
> the workaround is 'make PYTHON=python3'.
>
> Fix it by autodetecting Python based on whether python[x]-config exists
> rather than just python[x] because both are needed for the build. Then
> -config is stripped to find the Python runtime.
>
> Testing
> =======
>
>  * Auto detect links with Python3 when the v3 devtools are installed
>    and only Python 2 runtime is installed
>  * Auto detect links with Python2 when both devtools are installed
>  * Sensible warning is printed if no Python devtools are installed
>  * 'make PYTHON=x' still automatically sets PYTHON_CONFIG=x-config
>  * 'make PYTHON=x' fails if x-config doesn't exist

If x is a valid python but no x-config is found in the system, the build
fails, instead of printing a warning like before. If we use this approach
I think [1] in the Makefile is never hit and needs to be cleaned up.

Thanks,
German

[1] https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/perf/Makefile.config?h=perf/core#n826:

>  * 'make PYTHON=python3' overrides Python2 devtools
>  * 'make PYTHON=python2' overrides Python3 devtools
>  * 'make PYTHON_CONFIG=x-config' works
>  * 'make PYTHON=x PYTHON_CONFIG=x' works
>  * 'make PYTHON=missing' reports an error
>  * 'make PYTHON_CONFIG=missing' reports an error
>
> Fixes: 79373082fa9d ("perf python: Autodetect python3 binary")
> Signed-off-by: James Clark <james.clark@arm.com>
> ---
>  tools/perf/Makefile.config | 39 ++++++++++++++++++++++++++------------
>  1 file changed, 27 insertions(+), 12 deletions(-)
>
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index 96ad944ca6a8..b3fbb746e7f0 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -239,18 +239,33 @@ ifdef PARSER_DEBUG
>  endif
>  
>  # Try different combinations to accommodate systems that only have
> -# python[2][-config] in weird combinations but always preferring
> -# python2 and python2-config as per pep-0394. If python2 or python
> -# aren't found, then python3 is used.
> -PYTHON_AUTO := python
> -PYTHON_AUTO := $(if $(call get-executable,python3),python3,$(PYTHON_AUTO))
> -PYTHON_AUTO := $(if $(call get-executable,python),python,$(PYTHON_AUTO))
> -PYTHON_AUTO := $(if $(call get-executable,python2),python2,$(PYTHON_AUTO))
> -override PYTHON := $(call get-executable-or-default,PYTHON,$(PYTHON_AUTO))
> -PYTHON_AUTO_CONFIG := \
> -  $(if $(call get-executable,$(PYTHON)-config),$(PYTHON)-config,python-config)
> -override PYTHON_CONFIG := \
> -  $(call get-executable-or-default,PYTHON_CONFIG,$(PYTHON_AUTO_CONFIG))
> +# python[2][3]-config in weird combinations in the following order of
> +# priority from lowest to highest:
> +#   * python3-config
> +#   * python-config
> +#   * python2-config as per pep-0394.
> +#   * $(PYTHON)-config (If PYTHON is user supplied but PYTHON_CONFIG isn't)
> +#
> +PYTHON_AUTO := python-config
> +PYTHON_AUTO := $(if $(call get-executable,python3-config),python3-config,$(PYTHON_AUTO))
> +PYTHON_AUTO := $(if $(call get-executable,python-config),python-config,$(PYTHON_AUTO))
> +PYTHON_AUTO := $(if $(call get-executable,python2-config),python2-config,$(PYTHON_AUTO))
> +
> +# If PYTHON is defined but PYTHON_CONFIG isn't, then take $(PYTHON)-config as if it was the user
> +# supplied value for PYTHON_CONFIG. Because it's "user supplied", error out if it doesn't exist.
> +ifdef PYTHON
> +  ifndef PYTHON_CONFIG
> +    PYTHON_CONFIG_AUTO := $(call get-executable,$(PYTHON)-config)
> +    PYTHON_CONFIG := $(if $(PYTHON_CONFIG_AUTO),$(PYTHON_CONFIG_AUTO),\
> +                          $(call $(error $(PYTHON)-config not found)))
> +  endif
> +endif
> +
> +# Select either auto detected python and python-config or use user supplied values if they are
> +# defined. get-executable-or-default fails with an error if the first argument is supplied but
> +# doesn't exist.
> +override PYTHON_CONFIG := $(call get-executable-or-default,PYTHON_CONFIG,$(PYTHON_AUTO))
> +override PYTHON := $(call get-executable-or-default,PYTHON,$(subst -config,,$(PYTHON_AUTO)))
>  
>  grep-libs  = $(filter -l%,$(1))
>  strip-libs  = $(filter-out -l%,$(1))