Re: Switch to nullptr?

[Daniel J Sebald]

On 04/28/2017 05:58 PM, John W. Eaton wrote:
> On 04/28/2017 06:13 PM, Rik wrote:
>
> > There are one or two places left in the code where I couldn't tell
> > whether switching would cause a problem so I left them alone.
> >
> > # This is wrapped in a Windows-only #ifdef.  I don't know what Microsoft
> > lib will return
> > corefcn/sysdep.cc:188:  if (hShell != NULL)
>
> This could just be
>
>   if (hShell)
>
> > dldfcn/__osmesa_print__.cc:126:  OSMesaContext ctx =
> > OSMesaCreateContextExt (OSMESA_RGBA, 16, 0, 0, NULL);
>
> I always converted any uses of NULL in C++ code to just be 0.  The
> function has to have a prototype and 0 should be fine.
>
> jwe

If I understand correctly, the danger in C++ is that overloaded 
functions are ambiguous when NULL is used, e.g., say there is some 
function for which

  void OSMesaCreateContextExt (,,,, int);
  void OSMesaCreateContextExt (,,,, drvr *);

then NULL for the last input will choose the former version.  Now, I 
doubt OSMesaCreatedContextExt is overloaded, but generally using 0 
instead of NULL effectively explicitly does the implicit cast that the 
use of NULL would result in.  It might be worth tacking on an explicit 
cast in those cases where 0 is used, e.g.,

  OSMesaCreateContextExt (OSMESA_RGBA, 16, 0, 0, (OSMesaContext)0);
  jobjectArray array = jni_env->NewObjectArray (n, scls, (jclass)0);

Dan