Re: [Xen-devel] [PATCH] xen/tools: support Python 2 and Python 3

[Doug Goldstein <cardoe@xxxxxxxxxx>]

On 2/22/18 6:54 AM, Andrew Cooper wrote:
> On 22/02/18 05:52, Doug Goldstein wrote:
>> These changes should make it possible to support modern Pythons as well
>> as the oldest Python 2 still supported.
>>
>> Signed-off-by: Doug Goldstein <cardoe@xxxxxxxxxx>
> 
> To the overall effect, this is definitely a good thing.  Some queries
> however...
> 

>> diff --git a/xen/tools/compat-build-header.py 
>> b/xen/tools/compat-build-header.py
>> index 32421b645b..546371225d 100755
>> --- a/xen/tools/compat-build-header.py
>> +++ b/xen/tools/compat-build-header.py
>> @@ -23,4 +23,4 @@ pats = [
>>  for line in sys.stdin.readlines():
>>      for pat in pats:
>>          line = re.subn(pat[0], pat[1], line)[0]
>> -    print line.rstrip()
>> +    sys.stdout.write(line.rstrip() + '\n')
> 
> Is there anything wrong with print(line.rstrip()) which is the more
> common way of doing this?

The other scripts in the repo avoided using print as a function which
was only added to Python 2.6 and newer if you use from __future__ import
print_function. The README in the repo still says Python 2.3 and newer
so I had assumed if I broke things prior to Python 2.6 it would be a
show stopper. While Python 2.3 was released July 29th 2003 and Python
2.6 was released Oct 1st 2008 I figured changing this requirement was
going to be met with the same difficultly I encountered last time
suggesting that we only support versions of build tools released in the
past decade.


> 
>> diff --git a/xen/tools/compat-build-source.py 
>> b/xen/tools/compat-build-source.py
>> index 595bc3ff58..8101290ebe 100755
>> --- a/xen/tools/compat-build-source.py
>> +++ b/xen/tools/compat-build-source.py
>> @@ -26,4 +26,4 @@ for pat in pats:
>>  for line in sys.stdin.readlines():
>>      for pat in pats:
>>          line = re.sub(pat[0], pat[1], line)
>> -    print line.rstrip()
>> +    sys.stdout.write(line.rstrip() + '\n')
>> diff --git a/xen/tools/gen-cpuid.py b/xen/tools/gen-cpuid.py
>> index 613b909c3d..d64f257816 100755
>> --- a/xen/tools/gen-cpuid.py
>> +++ b/xen/tools/gen-cpuid.py
>> @@ -3,6 +3,13 @@
>>  
>>  import sys, os, re
>>  
>> +if (sys.version_info > (3, 0)):
>> +    def long(x):
>> +        return x
> 
> Strictly speaking, return int(x), however...
> 
>> +
>> +    def xrange(x):
>> +        return range(x)
>> +
>>  class Fail(Exception):
>>      pass
>>  
>> @@ -98,13 +105,13 @@ def parse_definitions(state):
>>  def featureset_to_uint32s(fs, nr):
>>      """ Represent a featureset as a list of C-compatible uint32_t's """
>>  
>> -    bitmap = 0L
>> +    bitmap = long(0)
>>      for f in fs:
>> -        bitmap |= 1L << f
>> +        bitmap |= long(1) << f
> 
> Having tested this out, I think the L suffixes can just be dropped:
> 
> Python 2.4.3 (#1, Sep 21 2011, 20:06:00)
> [GCC 4.1.2 20080704 (Red Hat 4.1.2-51)] on linux2
> Type "help", "copyright", "credits" or "license" for more information.
>>>> bitmap = 0
>>>> type(bitmap)
> <type 'int'>
>>>> for x in xrange(80): bitmap |= 1 << x
> ...
>>>> type(bitmap)
> <type 'long'>
>>>>
> 
> I don't recall why I wrote it like this, but I don't think its
> necessary.  As a result, you shouldn't need to define long above.
> 
> ~Andrew

Python 2.4 and newer will properly extend for you but Python 2.3 will
not and I was aiming to still support Python 2.3. Now this is all
theoretical since I can't find any boxes with Python 2.3 anywhere and
I'm not interested in building it.

-- 
Doug Goldstein

Attachment: signature.asc
Description: OpenPGP digital signature

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel