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User Defined C Function

From: "Nathan Thatcher" <n8thatcher(at)gmail(dot)com>
To: pgsql-interfaces(at)postgresql(dot)org
Subject: User Defined C Function
Date: 2008-05-01 23:18:29
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-interfaces
I have been creating some user defined C functions using minGW and
postgreSQL 8.3. Everything works great when I use integers,
timestamps, points, etc. I have compiled, linked, created, and tested
multiple function and aggregates.

The problem occurs when I have a text parameter and need to use
PG_GETARG_TEXT_P(n). The code compiles just fine but linking fails.
Here is an example:

#include "postgres.h"
#include "fmgr.h"



	text *t = PG_GETARG_TEXT_P(1);
	int32 i = PG_GETARG_INT32(0);

The error:
X)function_name.o:function_name.c: undefined reference to `pg_detoast_datum'
If I comment out the text *t line then it compiles, links, and
executes just fine.

The problem (I am assuming it is the same problem) also manifests
itself when I make a call to palloc. I get 2 errors

X) finalagent.o:finalagent.c: undefined reference to
X) finalagent.o:finalagent.c: undefined reference to `MemoryContextAlloc'

Some people have said that this error should just be ignored and it
will sort itself out at run-time. That sounds swell but how do I get
my linker to ignore these errors?

Other people have said that pg_detoast_datum is a backend function and
shouldn't be referenced at all, but it is right there in fmgr.h which
is obviously required for creating functions under the V1 calling

For reference, I am on Windows XP SP2. I installed postgreSQL 8.3 from
the msi and selected to include the Development components (Include
Files, Library Files, Tools and utilities). The compiler is including
the following directories:


I added both C:\PostgreSQL\8.3\lib and C:\PostgreSQL\8.3\bin to my
linker hoping that maybe it would work. It didn't.

Any information, insight, tips, or criticism would be welcomed and appreciated.


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