src: rewrite remote protocol checker in Python

As part of a goal to eliminate Perl from libvirt build tools,
rewrite the pdwtags processing script in Python.

The original inline shell and perl code was completely
unintelligible. The new python code is a manual conversion
that attempts todo basically the same thing.

Tested-by: Cole Robinson <crobinso@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

scripts/check-remote-protocol.py

@@ -0,0 +1,134 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2019 Red Hat, Inc.
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library.  If not, see
+# <http://www.gnu.org/licenses/>.
+#
+# This uses pdwtags to check remote protocol defs
+#
+# * the "split" splits on the /* DD */ comments, so that $p iterates
+#     through the struct definitions.
+# * process only "struct remote_..." entries
+# * remove comments and preceding TAB throughout
+# * remove empty lines throughout
+# * remove white space at end of buffer
+
+import os
+import os.path
+import re
+import subprocess
+import sys
+
+cc = sys.argv[1]
+objext = sys.argv[2]
+proto_lo = sys.argv[3]
+expected = sys.argv[4]
+
+proto_lo = proto_lo.replace("/", "/.libs/")
+
+ccargv = cc.split(" ")
+ccargv.append("-v")
+ccproc = subprocess.Popen(ccargv, stdout=subprocess.PIPE,
+                          stderr=subprocess.STDOUT)
+out, err = ccproc.communicate()
+out = out.decode("utf-8")
+if out.find("clang") != -1:
+    print("WARNING: skipping pdwtags test with Clang", file=sys.stderr)
+    sys.exit(0)
+
+
+def which(program):
+    def is_exe(fpath):
+        return (os.path.isfile(fpath) and
+                os.access(fpath, os.X_OK))
+
+    fpath, fname = os.path.split(program)
+    if fpath:
+        if is_exe(program):
+            return program
+    else:
+        for path in os.environ["PATH"].split(os.pathsep):
+            exe_file = os.path.join(path, program)
+            if is_exe(exe_file):
+                return exe_file
+
+    return None
+
+
+pdwtags = which("pdwtags")
+if pdwtags is None:
+    print("WARNING: you lack pdwtags; skipping the protocol test",
+          file=sys.stderr)
+    print("WARNING: install the dwarves package to get pdwtags",
+          file=sys.stderr)
+    sys.exit(0)
+
+proto_o = proto_lo.replace(".lo", ".o")
+
+if not os.path.exists(proto_o):
+    raise Exception("Missing %s", proto_o)
+
+pdwtagsproc = subprocess.Popen(["pdwtags", "--verbose", proto_o],
+                               stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+out, err = pdwtagsproc.communicate()
+out = out.decode("utf-8")
+err = err.decode("utf-8")
+
+if out == "" and err != "":
+    print("WARNING: no output, pdwtags appears broken:", file=sys.stderr)
+    for l in err.strip().split("\n"):
+        print("WARNING: %s" % l, file=sys.stderr)
+    print("WARNING: skipping the remote protocol test", file=sys.stderr)
+    sys.exit(0)
+
+# With pdwtags 1.8, --verbose output includes separators like these:
+# /* 93 */
+# /* <0> (null):0 */
+# with the second line omitted for intrinsic types.
+# Whereas with pdwtags 1.3, they look like this:
+# /* <2d2> /usr/include/libio.h:180 */
+# The alternation of the following regexps matches both cases.
+r1 = r'''/\* \d+ \*/'''
+r2 = r'''/\* <[0-9a-fA-F]+> \S+:\d+ \*/'''
+
+libs_prefix = "remote_|qemu_|lxc_|admin_"
+other_prefix = "keepalive|vir(Net|LockSpace|LXCMonitor)"
+struct_prefix = "(" + libs_prefix + "|" + other_prefix + ")"
+
+n = 0
+bits = re.split(r'''\n*(?:%s|%s)\n''' % (r1, r2), out)
+actual = ["/* -*- c -*- */"]
+
+for bit in bits:
+    if re.search(r'''^(struct|enum)\s+''' + struct_prefix, bit):
+        bit = re.sub(r'''\t*/\*.*?\*/''', "", bit)
+        bit = re.sub(r'''\s+\n''', '''\n''', bit)
+        bit = re.sub(r'''\s+$''', "", bit)
+        bit = re.sub(r'''\t''', "        ", bit)
+        actual.append(bit)
+        n = n + 1
+
+if n < 1:
+    print("WARNING: No structs/enums matched. Your", file=sys.stderr)
+    print("WARNING: pdwtags program is probably too old", file=sys.stderr)
+    print("WARNING: skipping the remote protocol test", file=sys.stderr)
+    print("WARNING: install dwarves-1.3 or newer", file=sys.stderr)
+    sys.exit(8)
+
+diff = subprocess.Popen(["diff", "-u", expected, "-"], stdin=subprocess.PIPE)
+actualstr = "\n".join(actual) + "\n"
+diff.communicate(input=actualstr.encode("utf-8"))
+
+sys.exit(diff.returncode)