4:51 a.m.
On Thu, Jan 15, 2015 at 10:42:39 +0000, Daniel Berrange wrote:
On Wed, Jan 14, 2015 at 08:08:16PM -0700, Eric Blake wrote:
> In some cases, it is very easy for downstream distros to backport
> enum values without requiring a .so bump. Keying the conditional
> code off of the upstream version where the enum value was added
> is not ideal, because downstream then has to patch that the feature
> is available in their build that still reports an earlier version
> number. For example, if RHEL 7 backports events from 1.2.11 into
> a build based on 1.2.8, building the python bindings would warn:
>
> libvirt-override.c: In function ‘libvirt_virConnectDomainEventRegisterAny’:
> libvirt-override.c:6653:5: warning: enumeration value ‘VIR_DOMAIN_EVENT_ID_TUNABLE’
not handled in switch [-Wswitch]
> switch ((virDomainEventID) eventID) {
> ^
> libvirt-override.c:6653:5: warning: enumeration value
‘VIR_DOMAIN_EVENT_ID_AGENT_LIFECYCLE’ not handled in switch [-Wswitch]
>
> The solution is simple - use feature-based probes instead of
> version probes. Since we already scrape the XML API document of
> whatever libvirt build we are binding, and that XML already
> documents any downstream enum additions, we can use those as the
> features for gating conditional compilation.
>
> * generator.py (enum): Track event id names.
> (buildStubs): Output define wrappers for events.
> * libvirt-override.c
> (libvirt_virConnectDomainEventBalloonChangeCallback)
> (libvirt_virConnectDomainEventPMSuspendDiskCallback)
> (libvirt_virConnectDomainEventDeviceRemovedCallback)
> (libvirt_virConnectDomainEventTunableCallback)
> (libvirt_virConnectDomainEventAgentLifecycleCallback)
> (libvirt_virConnectDomainEventRegisterAny): Use them.
>
> Signed-off-by: Eric Blake <eblake(a)redhat.com>
> ---
>
> I mentioned this idea on the list a while back, and finally
> got time to code it up in a much nicer way than my initial
> attempt that would have polluted libvirt.h proper.
> https://www.redhat.com/archives/libvir-list/2014-October/msg00186.html
>
> I'm relatively weak at python, and welcome to suggestions on how
> to avoid the long line in generator.py (maybe a regex match on
> VIR_.*_EVENT_ID_, but what's the canonical way to write that in
> python?)
>
> generator.py | 11 +++++++++--
> libvirt-override.c | 46 +++++++++++++++++++++++-----------------------
> 2 files changed, 32 insertions(+), 25 deletions(-)
>
> diff --git a/generator.py b/generator.py
> index cf044c9..4fd6d55 100755
> --- a/generator.py
> +++ b/generator.py
> @@ -9,6 +9,7 @@ qemu_functions = {}
> enums = {} # { enumType: { enumConstant: enumValue } }
> lxc_enums = {} # { enumType: { enumConstant: enumValue } }
> qemu_enums = {} # { enumType: { enumConstant: enumValue } }
> +event_ids = []
>
> import os
> import sys
> @@ -219,6 +220,8 @@ def lxc_function(name, desc, ret, args, file, module, cond):
> def enum(type, name, value):
> if type not in enums:
> enums[type] = {}
> + if name.startswith('VIR_DOMAIN_EVENT_ID_') or
name.startswith('VIR_NETWORK_EVENT_ID_'):
> + event_ids.append(name)
If you use brackets you can break the line without confusing
python eg
if (name.startswith('VIR_DOMAIN_EVENT_ID_') or
name.startswith('VIR_NETWORK_EVENT_ID_')):
> if value == 'VIR_TYPED_PARAM_INT':
> value = 1
> elif value == 'VIR_TYPED_PARAM_UINT':
> @@ -910,10 +913,10 @@ def buildStubs(module, api_xml):
> wrapper_file = "build/%s.c" % module
>
> include = open(header_file, "w")
> - include.write("/* Generated */\n\n")
> + include.write("/* Generated by generator.py */\n\n")
>
> export = open(export_file, "w")
> - export.write("/* Generated */\n\n")
> + export.write("/* Generated by generator.py */\n\n")
>
> wrapper = open(wrapper_file, "w")
> wrapper.write("/* Generated by generator.py */\n\n")
> @@ -943,6 +946,10 @@ def buildStubs(module, api_xml):
> # Write C pointer conversion functions.
> for classname in primary_classes:
> print_c_pointer(classname, wrapper, export, include)
> + # Write define wrappers around event id enums
> + include.write("\n")
> + for event_id in event_ids:
> + include.write("#define %s %s\n" % (event_id, event_id))
I'm not seeing the point of adding this define ?
...
> -#if LIBVIR_CHECK_VERSION(0, 10, 0)
> +#ifdef VIR_DOMAIN_EVENT_ID_BALLOON_CHANGE
Without that define, you can't check for the events using ifdef,
C preprocessor doesn't see enum items.
Jirka