Re: [PATCH] Dynamic growable arrays for internal use

[Florian Weimer <fweimer at redhat dot com>]

On 04/24/2017 04:06 PM, Joseph Myers wrote:
> On Sat, 22 Apr 2017, Florian Weimer wrote:
>
> > +/* To use the dynarray facility, you need to include
> > +   <malloc/dynarray-skeleton.c> and define the parameter macros
> > +   documented in that file.
> > +
> > +   A minimal example which provides a growing list of integers can be
> > +   defined like this:
> > +
> > +     struct int_array
> > +     {
> > +       int *array;
> > +       size_t length;
> > +     };
> > +
> > +     #define DYNARRAY_STRUCT dynarray_int
> > +     #define DYNARRAY_ELEMENT int
> > +     #define DYNARRAY_PREFIX dynarray_int_
> > +     #define DYNARRAY_FINAL_TYPE struct int_array
> > +     #include <malloc/dynarray-skeleton.c>
> > +
> > +   To create a three-element array with elements 1, 2, 3, use this
> > +   code:
> > +
> > +     struct dynarray_int dyn;
> > +     dynarray_int_init (&dyn);
> > +     int *place = dynarray_int_emplace (&dyn);
>
> Should this first call to dynarray_int_emplace outside the loop be there?
> The result doesn't seem to be used.

Right, I didn't test the example at all.  There are many errors in it. 
The corrected version follows.

   A minimal example which provides a growing list of integers can be
   defined like this:

     struct int_array
     {
       int *array;
       size_t length;
     };

     #define DYNARRAY_STRUCT dynarray_int
     #define DYNARRAY_ELEMENT int
     #define DYNARRAY_PREFIX dynarray_int_
     #define DYNARRAY_FINAL_TYPE struct int_array
     #include <malloc/dynarray-skeleton.c>

   To create a three-element array with elements 1, 2, 3, use this
   code:

     struct dynarray_int dyn;
     dynarray_int_init (&dyn);
     for (int i = 1; i <= 3; ++i)
       {
         int *place = dynarray_int_emplace (&dyn);
         assert (place != NULL);
         *place = i;
       }
     struct int_array result;
     bool ok = dynarray_int_finalize (&dyn, &result);
     assert (ok);
     assert (result.length == 3);
     assert (result.array[0] == 1);
     assert (result.array[1] == 2);
     assert (result.array[2] == 3);
     free (result.array);

I wish we had doctests for these kinds of things.

Does anyone have comments about the interface and implementation?

Thanks,
Florian