Re: [PATCH] Use the environment variable PYTHON if defined

[Michael Witten <mfwitten@gmail.com>]

On Sun, 10 Apr 2011 00:12:45 +0530, Raghavendra D Prabhu wrote:

> I have a question regarding the message that is displayed.
> It says "No Python.h found" when variable PYTHON is not set
> correctly, it would be better if it said "No Python.h for
> Python 2.x found" since the header file supplied by Py3k is
> also Python.h and in the rare case of only Py3k installed on
> the box, it may be confusing.

Well...

If PYTHON or PYTHON_CONFIG don't point to an executable, then
there is a complaint about no executable being found.

If PYTHON (or, more specifically, PYTHON_CONFIG) points to the
Python *3* binary, then the message will be about Python 3 being
incompatible.

If PYTHON or PYTHON_CONFIG point to an executable that does not
provide a suitable `Python.h', then it says `No Python.h found'.

Thus, I think all of the cases are covered pretty well.
In particular, let's say that somebody triggers the third case,
but is confused because he does indeed have Python 3 with a valid
Python.h installed. That `No Python.h found' message will cause
him to look at how he configured PYTHON{,_CONFIG}, and he'll
see that he used the wrong executable (which is probably a
fairly unlikely scenario, anyway). Thus, he will configure the
right variable to point to the Python 3 executable, only to
get a message that Python 3 is incompatible. Thus, he will then
know that Python 2 is required.

I suppose, though, we could simplify the experience for the user
by giving a hint earlier on that Python 2 is required.

The patch that follows fulfills your request. My advice is to
save this email to /tmp/email and then apply it over the last
couple of patches like this:

  $ git apply /tmp/email
  $ git commit -a --amend -C HEAD

diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index 1fd46bf..b5276c7 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -522,7 +522,7 @@ else
       FLAGS_PYTHON_EMBED := $(PYTHON_EMBED_CCOPTS) $(PYTHON_EMBED_LDOPTS)
 
       ifneq ($(call try-cc,$(SOURCE_PYTHON_EMBED),$(FLAGS_PYTHON_EMBED)),y)
-        $(call disable-python,Python.h)
+        $(call disable-python,Python.h (for Python 2.x))
       else
 
         ifneq ($(call try-cc,$(SOURCE_PYTHON_VERSION),$(FLAGS_PYTHON_EMBED)),y)