[libvirt] [PATCH v3 01/35] util: alloc: add macros for implementing automatic cleanup functionality

[Sukrit Bhatnagar]

On Thu, 12 Jul 2018 at 22:09, Erik Skultety <eskultet at redhat.com> wrote:
>
> On Sat, Jun 30, 2018 at 02:30:05PM +0530, Sukrit Bhatnagar wrote:
> > New macros are introduced which help in adding GNU C's cleanup
> > attribute to variable declarations. Variables declared with these
> > macros will have their allocated memory freed automatically when
> > they go out of scope.
> >
> > Signed-off-by: Sukrit Bhatnagar <skrtbhtngr at gmail.com>
> > ---
> >  src/util/viralloc.h | 44 ++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 44 insertions(+)
> >
> > diff --git a/src/util/viralloc.h b/src/util/viralloc.h
> > index 69d0f90..5c1d0d5 100644
> > --- a/src/util/viralloc.h
> > +++ b/src/util/viralloc.h
> > @@ -596,4 +596,48 @@ void virAllocTestInit(void);
> >  int virAllocTestCount(void);
> >  void virAllocTestOOM(int n, int m);
> >  void virAllocTestHook(void (*func)(int, void*), void *data);
> > +
> > +# define VIR_AUTOPTR_TYPE_NAME(type) type##AutoPtr
> > +# define VIR_AUTOPTR_FUNC_NAME(type) type##AutoPtrFree
> > +
> > +/**
> > + * VIR_DEFINE_AUTOPTR_FUNC:
> > + * @type: type of the variable to be freed automatically
> > + * @func: cleanup function to be automatically called
> > + *
> > + * This macro defines a function for automatic freeing of
> > + * resources allocated to a variable of type @type. This newly
> > + * defined function works as a necessary wrapper around @func.
> > + */
> > +# define VIR_DEFINE_AUTOPTR_FUNC(type, func) \
> > +    typedef type *VIR_AUTOPTR_TYPE_NAME(type); \
>
> So, it's not visible at first glance how ^this typedef is used...
>
> > +    static inline void VIR_AUTOPTR_FUNC_NAME(type)(type **_ptr) \
> > +    { \
> > +        if (*_ptr) \
> > +            (func)(*_ptr); \
> > +        *_ptr = NULL; \
> > +    } \
>
> ...therefore I'd write it explicitly as
>
> VIR_AUTOPTR_FUNC_NAME(type)(VIR_AUTOPTR_TYPE_NAME(type) *_ptr)
>
> > +
> > +# define VIR_AUTOPTR(type) \
> > +    __attribute__((cleanup(VIR_AUTOPTR_FUNC_NAME(type)))) VIR_AUTOPTR_TYPE_NAME(type)
> > +
>
> Also, since we're going to use it like this:
> VIR_AUTOPTR(virDomainDef) foo
>
> instead of this:
> VIR_AUTOPTR(virDomainDefPtr) foo
>
> why do we need VIR_AUTOPTR_TYPE_NAME anyway, since you could just use
> "type *" in the VIR_AUTOPTR macro definition and that should work for external
> types as well.

I agree. We don't really need it. Here is how the code will look after
the changes
you suggested:

# define VIR_AUTOPTR_FUNC_NAME(type) type##AutoPtrFree

# define VIR_DEFINE_AUTOPTR_FUNC(type, func) \
    static inline void VIR_AUTOPTR_FUNC_NAME(type)(type **_ptr) \
    { \
        if (*_ptr) \
            (func)(*_ptr); \
        *_ptr = NULL; \
    } \

# define VIR_AUTOFREE(type) __attribute__((cleanup(virFree))) type

# define VIR_AUTOPTR(type) \
    __attribute__((cleanup(VIR_AUTOPTR_FUNC_NAME(type)))) type *


Shall I proceed to send the first series of patches?