[Xen-devel] [PATCH v3 3/3] xen/build: Automatically locate a suitable python interpreter

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Needing to pass PYTHON=python3 into hypervisor builds is irritating and
unnecessary.  Locate a suitable interpreter automatically, defaulting to Py3
if it is available.

Reported-by: Steven Haigh <netwiz@xxxxxxxxx>
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
CC: Ian Jackson <ian.jackson@xxxxxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Julien Grall <julien@xxxxxxx>
CC: Steven Haigh <netwiz@xxxxxxxxx>
CC: Juergen Gross <jgross@xxxxxxxx>

v2:
 * Cope with `which` not being present in the system.
 * Only evaulate the shell command one, rather than once per $(PTHON) usage

For 4.13.  This is a very-nice-to-have WRT our Py3-clean intention.
---
 xen/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/xen/Makefile b/xen/Makefile
index 949ca6eb03..f36a5bc6c0 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -13,6 +13,11 @@ export XEN_BUILD_TIME        ?= $(shell LC_ALL=C date +%T)
 export XEN_BUILD_HOST  ?= $(shell hostname)
 export XEN_CONFIG_EXPERT ?= n
 
+# Best effort attempt to find a python interpreter, defaulting to Python 3 if
+# available.  Fall back to just `python` if `which` is nowhere to be found.
+PYTHON_INTERPRETER     := $(word 1,$(shell which python3 python python2 
2>/dev/null) python)
+export PYTHON          ?= $(PYTHON_INTERPRETER)
+
 export BASEDIR := $(CURDIR)
 export XEN_ROOT := $(BASEDIR)/..
 
-- 
2.11.0


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