RE: [PATCH v4 3/4] perf jevents: Switch build to use jevents.py

From: David Laight <David.Laight@ACULAB.COM>
To: 'Ian Rogers' <rogers.email@gmail.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	"Arnaldo Carvalho de Melo" <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	"Alexander Shishkin" <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
	John Garry <john.garry@huawei.com>,
	"Kan Liang" <kan.liang@linux.intel.com>,
	Andi Kleen <ak@linux.intel.com>,
	"Zhengjun Xing" <zhengjun.xing@linux.intel.com>,
	Felix Fietkau <nbd@nbd.name>, Qi Liu <liuqi115@huawei.com>,
	Like Xu <likexu@tencent.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
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	<linux-perf-users@vger.kernel.org>,
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	Caleb Biggers <caleb.biggers@intel.com>,
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	Kshipra Bopardikar <kshipra.bopardikar@intel.com>
Cc: Stephane Eranian <eranian@google.com>, Ian Rogers <irogers@google.com>
Subject: RE: [PATCH v4 3/4] perf jevents: Switch build to use jevents.py
Date: Wed, 15 Jun 2022 10:44:50 +0000	[thread overview]
Message-ID: <9951ad2acd3d4454b39c4862da75d913@AcuMS.aculab.com> (raw)
In-Reply-To: <20220615030438.51477-4-irogers@google.com>

From: Ian Rogers
> Sent: 15 June 2022 04:05
> 
> Generate pmu-events.c using jevents.py rather than the binary built from
> jevents.c. Add a new config variable NO_JEVENTS that is set when there
> is no architecture json or an appropriate python interpreter isn't present.
> When NO_JEVENTS is defined the file pmu-events/empty-pmu-events.c is copied
> and used as the pmu-events.c file.
> 
...
> +    # jevents.py uses f-strings present in Python 3.6 released in Dec. 2016.
> +    JEVENTS_PYTHON_GOOD := $(shell $(PYTHON) -c 'import sys;print("1" if(sys.version_info.major >= 3
> and sys.version_info.minor >= 6) else "0")')

You probably want a "2>/dev/null" in there.

I also think I remember seeing a `which python` in one of these patches.
'which' is a bourne shell script that is trying to emulate a csh builtin.
It can't actually work, and ISTR one of the distros might be
trying to remove it.
In a traditional bourne shell you should use `type python`, the posix
equivalent (which any shell written in the last 30 years out to get
right) is `command -V python`.
Both type and command have to be shell builtins.
Although I suspect some shells get command -V wrong.

	David

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