Re: Problem returning strings with pgsql 8.3.x

On Tue, May 13, 2008 at 8:19 AM, Josh Tolley <eggyknap@gmail.com> wrote:
> On Tue, May 13, 2008 at 8:01 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>  > Martijn van Oosterhout <kleptog@svana.org> writes:
>  >  > On Mon, May 12, 2008 at 11:23:17PM -0600, Josh Tolley wrote:
>  >  >> SPI_push();
>  >  >> retval =
>  >  >> InputFunctionCall(&flinfo, lolVarGetString(returnVal, true),
>  >  >> resultTypeIOParam, -1);
>  >  >> SPI_pop();
>  >
>  >  > Won't this cause the return value to be allocated inside a new memory
>  >  > block which gets freeds at the SPI_pop?
>  >
>  >  The SPI_pop in itself is harmless ... the problem is the SPI_finish
>  >  further down, which will release all simple palloc's done within the
>  >  SPI function context.  What he needs is something comparable to this bit
>  >  in plpgsql:
>  >
>  >             /*
>  >              * If the function's return type isn't by value, copy the value
>  >              * into upper executor memory context.
>  >              */
>  >             if (!fcinfo->isnull && !func->fn_retbyval)
>  >             {
>  >                 Size        len;
>  >                 void       *tmp;
>  >
>  >                 len = datumGetSize(estate.retval, false, func->fn_rettyplen);
>  >                 tmp = SPI_palloc(len);
>  >                 memcpy(tmp, DatumGetPointer(estate.retval), len);
>  >                 estate.retval = PointerGetDatum(tmp);
>  >             }
>  >
>  >  ie, push the data into something allocated with SPI_palloc().
>
>  I'll give this a shot as soon as I can... many thanks
>
>
>  >  I would bet large amounts of money that the problem is not "new in
>  >  8.3.0", either.  Perhaps Josh was not testing in an --enable-cassert
>  >  (CLOBBER_FREED_MEMORY) build before.
>
>  I'll check... that's definitely not unlikely. Again, thanks.
>
>  - Josh
>

Proper (I hope) use of SPI_palloc() took care of this. And yes, the
8.2.x version I was using without problem was compiled without
enable-cassert. Once again, thanks.

- Josh / eggyknap