Re: C++ User-defined functions

Thanks Craig,

I'm trying to compile a very simple test with Visual Studio (2008), but I get the following errors:

c:\program files\postgresql\8.3\include\server\pg_config_os.h(188) : error C2011: 'timezone' : 'struct' type redefinition

c:\program files\postgresql\8.3\include\server\pg_config_os.h(188) : see declaration of 'timezone'
c:\program files\postgresql\8.3\include\server\pg_config_os.h(197) : error C2011: 'itimerval' : 'struct' type redefinition

c:\program files\postgresql\8.3\include\server\pg_config_os.h(197) : see declaration of 'itimerval'
c:\program files\postgresql\8.3\include\server\c.h(97) : fatal error C1083: Cannot open include file: 'libintl.h': No such file or directory

I must be doing something wrong - I don't even have a libintl.h on my drive...

This is my .cpp file:

#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif

#define _USE_32BIT_TIME_T

#include "postgres.h"
#include <string.h>
#include "fmgr.h"

/* by value */

PG_FUNCTION_INFO_V1(add_one);

Datum
add_one(PG_FUNCTION_ARGS)
{
int32 arg = PG_GETARG_INT32(0);

PG_RETURN_INT32(arg + 1);
}

If you can help, that would be wonderful.

Thanks a lot,

George.

> Date: Tue, 10 Mar 2009 02:35:34 +0900
> From: craig(at)postnewspapers(dot)com(dot)au
> To: oakmang(at)hotmail(dot)com
> CC: pgsql-general(at)postgresql(dot)org
> Subject: Re: [GENERAL] C++ User-defined functions
>
> George Oakman wrote:
>
> > I am trying to write a user-defined function in C++. Most examples are give in plain C. I would be very grafeful for a sample program/code-snippet in C++.
>
> It's just like any other C/C++ code mixing. You must make sure that any
> C-only headers are included within an `extern "C"' block, and declare
> any functions that'll be accessed via dlopen() etc as 'extern "C"' too.
> You may only use POD types, arrays of POD types, and structs of POD
> types (with no methods) in calls to/from C code.
>
> In other words, all PostgreSQL must see is plain C code, but your
> 'extern "C"' functions may call C++ methods and work with C++ objects
> internally.
>
> There's lots more information about this on the Internet. Just look for
> generic resources on calling C from C++ and vice versa.
>
> (I don't *think* there are any issues with libstdc++, though you'd
> probably have to make sure that no other program linked into Pg brings
> in a different version of libstdc++.)
>
> --
> Craig Ringer
>
> --
> Sent via pgsql-general mailing list (pgsql-general(at)postgresql(dot)org)
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