Re: mxIs* functions now return bool

[John W. Eaton]

On 09/11/2016 01:29 AM, Rik wrote:
> 9/10/16
> I've been working on improving the MEX interface in Octave.  One of the
> things I noticed is that the predicate tests in Matlab are all returning a
> bool, whereas in Octave they return an int.  A predicate test might be
> something like mxIsScalar or mxIsComplex.  Does anyone see a problem with
> changing the function prototypes to return bool?
>
> extern OCTINTERP_API int mxIsComplex (const mxArray *ptr);
> =>
> extern OCTINTERP_API bool mxIsComplex (const mxArray *ptr);

I suspect this is a relatively recent change in Matlab (for some value 
of relatively recent).  I'm pretty sure they used to return int.

> One of the things I don't understand is that the C language didn't have a
> bool type until C99, and even then it was necessary to #include <stdbool.h>
> in order to access it.  However, I accidentally coded mxIsScalar to return
> bool and it has compiled correctly.  The only thing I see at the top of
> mexproto.h is
>
> #if defined (__cplusplus)
> #  include <cstdlib>
> extern "C" {
> #else
> #  include <stdlib.h>
> #endif
>
> When I run 'mex -v ...' I can see that the compiler is gcc, not g++, so I
> don't think the first branch is being taken.  Should I worry and add the
> include for stdbool.h when compiling with a straight C compiler?

If add -save-temps to the compiler command that is used and then look at 
the generated .i  file can you see where bool is defined?

If I compile the simple program "bool x;" with gcc, it errors on the 
undefined bool type.  So I think there must be some place that bool is 
being defined.

But I don't think it would hurt to include stdbool.h along with 
stdlib.h.  If that causes trouble, I'm sure we'll hear about it.

jwe