[Mesa-dev] [PATCH] mesa: Fix wrong sizeof argument in _math_matrix_copy.

[Jose Fonseca]

----- Original Message -----
> On Sun, Jul 29, 2012 at 6:54 PM, Vinson Lee <vlee at freedesktop.org>
> wrote:
> > Fixes Coverity wrong sizeof argument defect.
> >
> > Signed-off-by: Vinson Lee <vlee at freedesktop.org>
> > ---
> >  src/mesa/math/m_matrix.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/src/mesa/math/m_matrix.c b/src/mesa/math/m_matrix.c
> > index 40f9229..7c4e9fd 100644
> > --- a/src/mesa/math/m_matrix.c
> > +++ b/src/mesa/math/m_matrix.c
> > @@ -1437,7 +1437,7 @@ void
> >  _math_matrix_copy( GLmatrix *to, const GLmatrix *from )
> >  {
> >     memcpy( to->m, from->m, sizeof(Identity) );
> > -   memcpy(to->inv, from->inv, sizeof(from->inv));
> > +   memcpy(to->inv, from->inv, sizeof(*from->inv));
> >     to->flags = from->flags;
> >     to->type = from->type;
> >  }
> 
> It would probably be good to update the preceding line as well.  It's
> kind of weird to use sizeof(X) when X isn't the source or dest to the
> memcpy().

Now you mention it, there is a reason for it.

This is the definition of GLmatrix:

  typedef struct {
     GLfloat *m;          /**< 16 matrix elements (16-byte aligned) */
     GLfloat *inv;        /**< optional 16-element inverse (16-byte aligned) */
     GLuint flags;        /**< possible values determined by (of \link
                           * MatFlags MAT_FLAG_* flags\endlink)
                           */
     enum GLmatrixtype type;
  } GLmatrix;

Therefore 

   memcpy(to->inv, from->inv, sizeof(from->inv));

or 

   memcpy(to->inv, from->inv, sizeof(*from->inv));

are busted, as none properly copies the full 16 elements.

Therefore, this

  memcpy(to->inv, from->inv, sizeof(Identity);

is how the memcpy should be done.

Jose