[Qemu-devel] [PATCH] scripts: Support building with Python 3

[David Michael <fedora.dm0@gmail.com>]

This allows building with "./configure --python=python3", where
the python3 program is at least version 3.6.  It preserves
compatibility with Python 2.  The changes include:

  - Avoiding "print" usage
  - Using bytes with files opened in binary mode
  - Switching .iteritems() to .items()
  - Adding fallback imports for functions moved to other modules

Signed-off-by: David Michael <fedora.dm0@gmail.com>
---

Hi,

I've been applying these changes when building on Fedora 26, which does
not include any Python 2 packages by default.  It was tested with Python
2.7 and 3.6.

I just saw the list of scripts that need updating on the mailing list,
and this doesn't cover all of them, but it is enough to build a binary
for running virtual machines with KVM.  Maybe it is still useful as a
starting point.

Thanks.

David

 configure            |  6 ++++--
 scripts/qapi.py      | 31 ++++++++++++++++++++-----------
 scripts/qapi2texi.py | 10 +++++-----
 scripts/signrom.py   |  4 ++--
 4 files changed, 31 insertions(+), 20 deletions(-)

diff --git a/configure b/configure
index dd73cce..09f4d68 100755
--- a/configure
+++ b/configure
@@ -1548,9 +1548,11 @@ fi
 
 # Note that if the Python conditional here evaluates True we will exit
 # with status 1 which is a shell 'false' value.
-if ! $python -c 'import sys; sys.exit(sys.version_info < (2,6) or sys.version_info >= (3,))'; then
+if ! $python -c 'import sys; sys.exit(sys.version_info >= (3,) and sys.version_info < (3,6))'; then
+  error_exit "Cannot use '$python', Python 3.6 or later is required." \
+      "Use --python=/path/to/python3 to specify a supported Python 3."
+elif ! $python -c 'import sys; sys.exit(sys.version_info < (2,6))'; then
   error_exit "Cannot use '$python', Python 2.6 or later is required." \
-      "Note that Python 3 or later is not yet supported." \
       "Use --python=/path/to/python to specify a supported Python."
 fi
 
diff --git a/scripts/qapi.py b/scripts/qapi.py
index 8aa2775..6450998 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -15,9 +15,11 @@ import errno
 import getopt
 import os
 import re
-import string
 import sys
-from ordereddict import OrderedDict
+try:
+    from collections import OrderedDict
+except ImportError:
+    from ordereddict import OrderedDict
 
 builtin_types = {
     'null':     'QTYPE_QNULL',
@@ -252,7 +254,7 @@ class QAPIDoc(object):
                                "'Returns:' is only valid for commands")
 
     def check(self):
-        bogus = [name for name, section in self.args.iteritems()
+        bogus = [name for name, section in self.args.items()
                  if not section.member]
         if bogus:
             raise QAPISemError(
@@ -308,7 +310,7 @@ class QAPISchemaParser(object):
                 if not isinstance(pragma, dict):
                     raise QAPISemError(
                         info, "Value of 'pragma' must be a dictionary")
-                for name, value in pragma.iteritems():
+                for name, value in pragma.items():
                     self._pragma(name, value, info)
             else:
                 expr_elem = {'expr': expr,
@@ -1574,7 +1576,7 @@ class QAPISchema(object):
 
     def _make_members(self, data, info):
         return [self._make_member(key, value, info)
-                for (key, value) in data.iteritems()]
+                for (key, value) in data.items()]
 
     def _def_struct_type(self, expr, info, doc):
         name = expr['struct']
@@ -1606,11 +1608,11 @@ class QAPISchema(object):
                 name, info, doc, 'base', self._make_members(base, info)))
         if tag_name:
             variants = [self._make_variant(key, value)
-                        for (key, value) in data.iteritems()]
+                        for (key, value) in data.items()]
             members = []
         else:
             variants = [self._make_simple_variant(key, value, info)
-                        for (key, value) in data.iteritems()]
+                        for (key, value) in data.items()]
             typ = self._make_implicit_enum_type(name, info,
                                                 [v.name for v in variants])
             tag_member = QAPISchemaObjectTypeMember('type', typ, False)
@@ -1625,7 +1627,7 @@ class QAPISchema(object):
         name = expr['alternate']
         data = expr['data']
         variants = [self._make_variant(key, value)
-                    for (key, value) in data.iteritems()]
+                    for (key, value) in data.items()]
         tag_member = QAPISchemaObjectTypeMember('type', 'QType', False)
         self._def_entity(
             QAPISchemaAlternateType(name, info, doc,
@@ -1735,7 +1737,11 @@ def c_enum_const(type_name, const_name, prefix=None):
         type_name = prefix
     return camel_to_upper(type_name) + '_' + c_name(const_name, False).upper()
 
-c_name_trans = string.maketrans('.-', '__')
+try:
+    c_name_trans = str.maketrans('.-', '__')
+except AttributeError:
+    import string
+    c_name_trans = string.maketrans('.-', '__')
 
 
 # Map @name to a valid C identifier.
@@ -1997,8 +2003,11 @@ def open_output(output_dir, do_c, do_h, prefix, c_file, h_file,
         if really:
             return open(name, opt)
         else:
-            import StringIO
-            return StringIO.StringIO()
+            try:
+                from StringIO import StringIO
+            except ImportError:
+                from io import StringIO
+            return StringIO()
 
     fdef = maybe_open(do_c, c_file, 'w')
     fdecl = maybe_open(do_h, h_file, 'w')
diff --git a/scripts/qapi2texi.py b/scripts/qapi2texi.py
index a317526..9a6fed9 100755
--- a/scripts/qapi2texi.py
+++ b/scripts/qapi2texi.py
@@ -147,7 +147,7 @@ def texi_member(member, suffix=''):
 def texi_members(doc, what, base, variants, member_func):
     """Format the table of members"""
     items = ''
-    for section in doc.args.itervalues():
+    for section in doc.args.values():
         # TODO Drop fallbacks when undocumented members are outlawed
         if section.content:
             desc = texi_format(str(section))
@@ -285,15 +285,15 @@ def texi_schema(schema):
 def main(argv):
     """Takes schema argument, prints result to stdout"""
     if len(argv) != 2:
-        print >>sys.stderr, "%s: need exactly 1 argument: SCHEMA" % argv[0]
+        sys.stderr.write("%s: need exactly 1 argument: SCHEMA\n" % argv[0])
         sys.exit(1)
 
     schema = qapi.QAPISchema(argv[1])
     if not qapi.doc_required:
-        print >>sys.stderr, ("%s: need pragma 'doc-required' "
-                             "to generate documentation" % argv[0])
+        sys.stderr.write("%s: need pragma 'doc-required' "
+                         "to generate documentation\n" % argv[0])
         sys.exit(1)
-    print texi_schema(schema)
+    sys.stdout.write(texi_schema(schema) + "\n")
 
 
 if __name__ == '__main__':
diff --git a/scripts/signrom.py b/scripts/signrom.py
index d1dabe0..0497a1c 100644
--- a/scripts/signrom.py
+++ b/scripts/signrom.py
@@ -18,7 +18,7 @@ fin = open(sys.argv[1], 'rb')
 fout = open(sys.argv[2], 'wb')
 
 magic = fin.read(2)
-if magic != '\x55\xaa':
+if magic != b'\x55\xaa':
     sys.exit("%s: option ROM does not begin with magic 55 aa" % sys.argv[1])
 
 size_byte = ord(fin.read(1))
@@ -33,7 +33,7 @@ elif len(data) < size:
     # Add padding if necessary, rounding the whole input to a multiple of
     # 512 bytes according to the third byte of the input.
     # size-1 because a final byte is added below to store the checksum.
-    data = data.ljust(size-1, '\0')
+    data = data.ljust(size-1, b'\0')
 else:
     if ord(data[-1:]) != 0:
         sys.stderr.write('WARNING: ROM includes nonzero checksum\n')
-- 
2.13.5