perf tools: Makefile: PYTHON{,_CONFIG} to bandage Python 3 incompatibility

Currently, Python 3 is not supported by perf's code; this
can cause the build to fail for systems that have Python 3
installed as the default python:

  python{,-config}

The Correct Solution is to write compatibility code so that
Python 3 works out-of-the-box.

However, users often have an ancillary Python 2 installed:

  python2{,-config}

Therefore, a quick fix is to allow the user to specify those
ancillary paths as the python binaries that Makefile should
use, thereby avoiding Python 3 altogether; as an added benefit,
the Python binaries may be installed in non-standard locations
without the need for updating any PATH variable.

This commit adds the ability to set PYTHON and/or PYTHON_CONFIG
either as environment variables or as make variables on the
command line; the paths may be relative, and usually only PYTHON
is necessary in order for PYTHON_CONFIG to be defined implicitly.
Some rudimentary error checking is performed when the user
explicitly specifies a value for any of these variables.

In addition, this commit introduces significantly robust makefile
infrastructure for working with paths and communicating with the
shell; it's currently only used for handling Python, but I hope
it will prove useful in refactoring the makefiles.

Thanks to:

  Raghavendra D Prabhu <rprabhu@wnohang.net>

for motivating this patch.

Acked-by: Raghavendra D Prabhu <rprabhu@wnohang.net>
Link: http://lkml.kernel.org/r/e987828e-87ec-4973-95e7-47f10f5d9bab-mfwitten@gmail.com
Signed-off-by: Michael Witten <mfwitten@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/tools/perf/feature-tests.mak b/tools/perf/feature-tests.mak
index b041ca67a2c..1b3342001e1 100644
--- a/tools/perf/feature-tests.mak
+++ b/tools/perf/feature-tests.mak
@@ -79,9 +79,15 @@ endef
 endif
 
 ifndef NO_LIBPYTHON
+define SOURCE_PYTHON_VERSION
+#include <Python.h>
+#if PY_VERSION_HEX >= 0x03000000
+	#error
+#endif
+int main(void){}
+endef
 define SOURCE_PYTHON_EMBED
 #include <Python.h>
-
 int main(void)
 {
 	Py_Initialize();