Checking that the derived class is larger than the requested parent
class saves us from some obvious mistakes, but as written, it does not
catch all the cases; in particular, it is easy to forget to update a
VIR_CLASS_NEW when changing the 'parent' member from virObject to
virObjectLockabale, but where the size checks don't catch that.  Add a
parameter for one more layer of sanity checking.

It would be cool if we could get gcc to stringize typeof(parent) into
the string name of that type, so that we could confirm that the
precise parent class is in use rather than just a struct that happens
to have the same size as the parent class.  But sizeof checks are
better than nothing.

Note that I did NOT change the fact that we require derived classes to
be larger (as the difference in size makes it easy to tell classes
apart), which means that even if a derived class has no functionality
to add (but rather exists for compiler-enforced type-safety), it must
still include a dummy member.  But I did fix the wording of the error
message to match the code.
Signed-off-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

I had to inspect the code to learn whether a final virObjectUnref()
calls ALL dispose callbacks in child-to-parent order (akin to C++
destructors), or whether I manually had to call a parent-class dispose
when writing a child class dispose method.  The answer is the
former. (Thankfully, since VIR_FREE wipes out pointers for safety,
even if I had guessed wrong, I probably would not have tripped over a
double-free fault when the parent dispose ran for the second time).  I
also had to read the code to learn if a dispose method was even
mandatory (it is not, although getting NULL through VIR_CLASS_NEW
requires a macro).  While at it, the VIR_CLASS_NEW macro requires that
the virObject component at offset 0 be reached through the name
'parent', not 'object'.
Signed-off-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

Add helper for utilizing __attribute__(cleanup())) for unref-ing
instances of sublasses of virObject.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

Require that all headers are guarded by a symbol named

  LIBVIRT_$FILENAME

where $FILENAME is the uppercased filename, with all characters
outside a-z changed into '_'.

Note we do not use a leading __ because that is technically a
namespace reserved for the toolchain.
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

This introduces a syntax-check script that validates header files use a
common layout:

  /*
   ...copyright header...
   */
  <one blank line>
  #ifndef SYMBOL
  # define SYMBOL
  ....content....
  #endif /* SYMBOL */

For any file ending priv.h, before the #ifndef, we will require a
guard to prevent bogus imports:

  #ifndef SYMBOL_ALLOW
  # error ....
  #endif /* SYMBOL_ALLOW */
  <one blank line>

The many mistakes this script identifies are then fixed.
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

Our virObject code relies heavily on the fact that the first
member of the class struct is type of virObject (or some
derivation of if). Let's check for that.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

So far we are repeating the following lines over and over:

  if (!(virSomeObjectClass = virClassNew(virClassForObject(),
                             "virSomeObject",
                             sizeof(virSomeObject),
                             virSomeObjectDispose)))
      return -1;

While this works, it is impossible to do some checking. Firstly,
the class name (the 2nd argument) doesn't match the name in the
code in all cases (the 3rd argument). Secondly, the current style
is needlessly verbose. This commit turns example into following:

  if (!(VIR_CLASS_NEW(virSomeObject,
                      virClassForObject)))
      return -1;
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

Rather than overload virObjectUnlock as commit id '77f4593b' has
done, create a separate virObjectRWUnlock API that will force the
consumers to make the proper decision regarding unlocking the
RWLock's. Similar to the RWLockRead and RWLockWrite, use the
virObjectGetRWLockableObj helper. This restores the virObjectUnlock
code to using the virObjectGetLockableObj.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

Instead of making virObjectLock be the entry point for two
different types of locks, let's create a virObjectRWLockWrite API
which will only handle the virObjectRWLockableClass objects.

Use the new virObjectRWLockWrite for the virdomainobjlist code
in order to handle the Add, Remove, Rename, and Load operations
that need to be very synchronous.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

Since the class it represents is based on virObjectRWLockableClass
and in order to make sure we differentiate just in case anyone somehow
believes they could use virObjectLockRead for a virObjectLockableClass,
let's rename the API to use the RW in the name. Besides the RW locks
refer to pthread_rwlock_{init|rdlock|wrlock|unlock|destroy} while the
other locks refer to pthread_mutex_{init|lock|unlock|destroy}.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

Up until now we only had virObjectLockable which uses mutexes for
mutually excluding each other in critical section. Well, this is
not enough. Future work will require RW locks so we might as well
have virObjectRWLockable which is introduced here.

Moreover, polymorphism is introduced to our code for the first
time. Yay! More specifically, virObjectLock will grab a write
lock, virObjectLockRead will grab a read lock then (what a
surprise right?). This has great advantage that an object can be
made derived from virObjectRWLockable in a single line and still
continue functioning properly (mutexes can be viewed as grabbing
write locks only). Then just those critical sections that can
grab a read lock need fixing. Therefore the resulting change is
going to be way smaller.

In order to avoid writer starvation, the object initializes RW
lock that prefers writers.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NPavel Hrdina <phrdina@redhat.com>

Alter to use more recent formatting guidelines
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

Extend it to a universal helper used for clearing lists of any objects.
Note that the argument type is specifically void * to allow implicit
typecasting.

Additionally add a helper that works on non-NULL terminated arrays once
we know the length.

I almost wrote a hash value free function that just called
VIR_FREE, then realized I couldn't be the first person to
do that.  Sure enough, it was worth factoring into a common
helper routine.

* src/util/virhash.h (virHashValueFree): New function.
* src/util/virhash.c (virHashValueFree): Implement it.
* src/util/virobject.h (virObjectFreeHashData): New function.
* src/libvirt_private.syms (virhash.h, virobject.h): Export them.
* src/nwfilter/nwfilter_learnipaddr.c (virNWFilterLearnInit): Use
common function.
* src/qemu/qemu_capabilities.c (virQEMUCapsCacheNew): Likewise.
* src/qemu/qemu_command.c (qemuDomainCCWAddressSetCreate):
Likewise.
* src/qemu/qemu_monitor.c (qemuMonitorGetBlockInfo): Likewise.
* src/qemu/qemu_process.c (qemuProcessWaitForMonitor): Likewise.
* src/util/virclosecallbacks.c (virCloseCallbacksNew): Likewise.
* src/util/virkeyfile.c (virKeyFileParseGroup): Likewise.
* tests/qemumonitorjsontest.c
(testQemuMonitorJSONqemuMonitorJSONGetBlockInfo): Likewise.
Signed-off-by: NEric Blake <eblake@redhat.com>

Recent changes to events (commit 8a29ffcf) resulted in new compile
failures on some targets (such as ARM OMAP5):
conf/domain_event.c: In function 'virDomainEventDispatchDefaultFunc':
conf/domain_event.c:1198:30: error: cast increases required alignment of
target type [-Werror=cast-align]
conf/domain_event.c:1314:34: error: cast increases required alignment of
target type [-Werror=cast-align]
cc1: all warnings being treated as errors

The error is due to alignment; the base class is merely aligned
to the worst of 'int' and 'void*', while the child class must
be aligned to a 'long long'.  The solution is to include a
'long long' (and for good measure, a function pointer) in the
base class to ensure correct alignment regardless of what a
child class may add, but to wrap the inclusion in a union so
as to not incur any wasted space.  On a typical x86_64 platform,
the base class remains 16 bytes; on i686, the base class remains
12 bytes; and on the impacted ARM platform, the base class grows
from 12 bytes to 16 bytes due to the increase of alignment from
4 to 8 bytes.

Reported by Michele Paolino and others.

* src/util/virobject.h (_virObject): Use a union to ensure that
subclasses never have stricter alignment than the parent.
* src/util/virobject.c (virObjectNew, virObjectUnref)
(virObjectRef): Adjust clients.
* src/libvirt.c (virConnectRef, virDomainRef, virNetworkRef)
(virInterfaceRef, virStoragePoolRef, virStorageVolRef)
(virNodeDeviceRef, virSecretRef, virStreamRef, virNWFilterRef)
(virDomainSnapshotRef): Likewise.
* src/qemu/qemu_monitor.c (qemuMonitorOpenInternal)
(qemuMonitorClose): Likewise.
Signed-off-by: NEric Blake <eblake@redhat.com>

When building with static analysis enabled, we turn on attribute
nonnull checking.  However, this caused the build to fail with:

../../src/util/virobject.c: In function 'virObjectOnceInit':
../../src/util/virobject.c:55:40: error: null argument where non-null required (argument 1) [-Werror=nonnull]

Creation of the virObject class is the one instance where the
parent class is allowed to be NULL.  Making things conditional
will let us keep static analysis checking for all other .c file
callers, without breaking the build on this one exception.

* src/util/virobject.c: Define witness.
* src/util/virobject.h (virClassNew): Use it to force most callers
to pass non-null parameter.

A great many virObject instances require a mutex, so introduce
a convenient class for this which provides a mutex. This avoids
repeating the tedious init/destroy code
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Currently all classes must directly inherit from virObject.
This allows for arbitrarily deep hierarchy. There's not much
to this aside from chaining up the 'dispose' handlers from
each class & providing APIs to check types.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

https://www.gnu.org/licenses/gpl-howto.html recommends that
the 'If not, see <url>.' phrase be a separate sentence.

* tests/securityselinuxhelper.c: Remove doubled line.
* tests/securityselinuxtest.c: Likewise.
* globally: s/;  If/.  If/

This introduces a fairly basic reference counted virObject type
and an associated virClass type, that use atomic operations for
ref counting.

In a global initializer (recommended to be invoked using the
virOnceInit API), a virClass type must be allocated for each
object type. This requires a class name, a "dispose" callback
which will be invoked to free memory associated with the object's
fields, and the size in bytes of the object struct.

eg,

   virClassPtr  connclass = virClassNew("virConnect",
                                        sizeof(virConnect),
                                        virConnectDispose);

The struct for the object, must include 'virObject' as its
first member

eg

  struct _virConnect {
    virObject object;

    virURIPtr uri;
  };

The 'dispose' callback is only responsible for freeing
fields in the object, not the object itself. eg a suitable
impl for the above struct would be

  void virConnectDispose(void *obj) {
     virConnectPtr conn = obj;
     virURIFree(conn->uri);
  }

There is no need to reset fields to 'NULL' or '0' in the
dispose callback, since the entire object will be memset
to 0, and the klass pointer & magic integer fields will
be poisoned with 0xDEADBEEF before being free()d

When creating an instance of an object, one needs simply
pass the virClassPtr eg

   virConnectPtr conn = virObjectNew(connclass);
   if (!conn)
      return NULL;
   conn->uri = virURIParse("foo:///bar")

Object references can be manipulated with

   virObjectRef(conn)
   virObjectUnref(conn)

The latter returns a true value, if the object has been
freed (ie its ref count hit zero)
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>