trace: introduce a formal group name for trace events

The declarations in the generated-tracers.h file are
assuming there's only ever going to be one instance
of this header, as they are not namespaced. When we
have one header per event group, if a single source
file needs to include multiple sets of trace events,
the symbols will all clash.

This change thus introduces a '--group NAME' arg to the
'tracetool' program. This will cause all the symbols in
the generated header files to be given a unique namespace.

If no group is given, the group name 'common' is used,
which is suitable for the current usage where there is
only one global trace-events file used for code generation.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Lluís Vilanova <vilanova@ac.upc.edu>
Message-id: 1475588159-30598-21-git-send-email-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

scripts/tracetool.py

diff --git a/scripts/tracetool.py b/scripts/tracetool.py
index f66e767..629b259 100755
--- a/scripts/tracetool.py
+++ b/scripts/tracetool.py
@@ -15,6 +15,8 @@
 
 import sys
 import getopt
+import os.path
+import re
 
 from tracetool import error_write, out
 import tracetool.backend
@@ -60,6 +62,15 @@
     else:
         sys.exit(1)
 
+def make_group_name(filename):
+    dirname = os.path.realpath(os.path.dirname(filename))
+    basedir = os.path.join(os.path.dirname(__file__), os.pardir)
+    basedir = os.path.realpath(os.path.abspath(basedir))
+    dirname = dirname[len(basedir) + 1:]
+
+    if dirname == "":
+        return "common"
+    return re.sub(r"/|-", "_", dirname)
 
 def main(args):
     global _SCRIPT
@@ -134,8 +145,10 @@
     with open(args[0], "r") as fh:
         events = tracetool.read_events(fh)
 
+    group = make_group_name(args[0])
+
     try:
-        tracetool.generate(events, arg_format, arg_backends,
+        tracetool.generate(events, group, arg_format, arg_backends,
                            binary=binary, probe_prefix=probe_prefix)
     except tracetool.TracetoolError as e:
         error_opt(str(e))