Re: [Xen-devel] [RFC 3/6] Introduce _xrealloc

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi,

Bringing back this discussion.

On 28/08/17 22:39, Goel, Sameer wrote:
> On 6/9/2017 3:44 AM, Wei Liu wrote:
> > On Thu, Jun 08, 2017 at 08:49:01PM +0100, Julien Grall wrote:
> > > CC the REST maintainers
> > >
> > > On 08/06/2017 20:30, Sameer Goel wrote:
> > > > Introduce a memory realloc function.
> > > >
> > > > Signed-off-by: Sameer Goel <sgoel@xxxxxxxxxxxxxx>
> > > > ---
> > > >   xen/common/xmalloc_tlsf.c | 13 +++++++++++++
> > > >   xen/include/xen/xmalloc.h |  1 +
> > > >   2 files changed, 14 insertions(+)
> > > >
> > > > diff --git a/xen/common/xmalloc_tlsf.c b/xen/common/xmalloc_tlsf.c
> > > > index b256dc5..52385a8 100644
> > > > --- a/xen/common/xmalloc_tlsf.c
> > > > +++ b/xen/common/xmalloc_tlsf.c
> > > > @@ -612,6 +612,19 @@ void *_xzalloc(unsigned long size, unsigned long align)
> > > >       return p ? memset(p, 0, size) : p;
> > > >   }
> > > >
> > > > +void *_xrealloc(void *p, unsigned long new_size, unsigned long align)
> > > > +{
> > > > +    void *new_p = _xmalloc(new_size, align);
> > > > +
> > > > +    if(new_p && p)
> > > Coding style: if ( ... )
> > >
> > > > +    {
> > > > +        memcpy(new_p, p, new_size);
> > This is wrong. How can you know if the area pointed to by p is at least
> > new_size bytes long?
> Agreed, I revisited the code and will remove _xrealloc and use xfree and 
> _xmalloc instead.
I am not sure why you choose to drop it completely. xfree is able to 
know the size of the buffer to free.
So you could find out the size and copy the right amount of data.

Note that having _xrealloc would be my preference over an open-coded 
version in the code.
Cheers,

--
Julien Grall

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