Further questions on interfacing to Postgres libpq

[rikki cattermole]

On 27/01/2018 5:11 AM, Joe wrote:
> An example test program that I'm using to learn D to C interfacing 
> (specifically calling the libpq library) has a call to a C function 
> declared as follows:
> 
>      void PQprint(FILE *fout,      /* output stream */
>                   const PGresult *res,
>                   const PQprintOpt *po);
> 
> PQprintOpt is a struct whose first six members are declared as 'pqbool' 
> which is in turn declared as "typedef char pqbool;" in the distributed 
> Postgres header file. I've defined an "alias pqbool = char;" in the D 
> file, which is pretty straightforward.

Use ubyte, not char.
char has a bunch of logic related to Unicode surrounding it which is 
clearly not the intent.

> The second of the six members has the name "align", which is a D 
> keyword. So I renamed it "align_" and I presume that won't cause any 
> problems.

You're good, layout+size just has to match not names of fields.

> To deal with the first argument to PQprint, I added "import 
> core.stdc.stdio : FILE;".  The question is how to pass the D "stdout" as 
> that argument.  The D compiler tells me I can't pass it as is (as was 
> done in C), because in D it's of type "File".

https://dlang.org/phobos/std_stdio.html#.File.getFP