Using Postgres connection functions

[Joe]

On Saturday, 13 January 2018 at 05:28:17 UTC, Joe wrote:
> Going beyond the connection, there are various other libpq 
> functions that use a similar pattern of values passed using 
> multiple parallel C arrays, e.g.,
>
>    PGresult *PQexecParams(PGconn *conn,
>                        const char *command,
>                        int nParams,
>                        const Oid *paramTypes,
>                        const char * const *paramValues,
>                        const int *paramLengths,
>                        const int *paramFormats,
>                        int resultFormat);
>
> Each of the `paramXxxxs' arguments are arrays (Oid is an alias 
> for uint).
> [...]

Focusing on the above function, suppose the first two parameter 
arrays are defined in a C program as:

     Oid paramTypes[] = {23, 25};
     char *paramValues[] = {"1", "abcde"};

which could be expressed in D as:

     Oid [] paramTypes = [23, 25];
     string [] paramValues = ["1", "abcde"];

I know the paramTypes could be passed as null, letting PG deduce 
the data types but suppose we have some reason to accumulate 
types, etc., in D slices.  I know the paramValues can be 
manipulated in a manner similar to the one shown in my first 
post, namely something like this:

    extern(C) char * [2] pvs;
    foreach (i, val; paramValues)
        pvs[i] = cast(char *)toStringz(val);

And then use "cast(const char **)pvs" for the paramValues 
argument. The only feedback that I received that was explicit to 
this approach was in response to my initial post, in which Adam 
D. Ruppe said that what I did was "decent".

So I have two lingering doubts:

1. Is malloc() the only way to allocate the arrays, either of 
Oid's, int's or char *'s, for passing to the libpq functions?  
IOW, isn't there a way to take advantage of D's 'new' (and thus 
the GC)?

2. How to convert a slice of Oid's or int's to an array of 
pointers suitable by processing by the libpq C function?  A 
technique similar to the previous one seems to work, e.g.,

     extern(C) Oid [2] pts;
     foreach (i, typ; paramTypes)
         pts[i] = typ;

But I'm not sure if it's really working (when I mistakenly had a 
* in the pts declaration, at one point it also seemed to work).