Incompatible library : Missing Magic Block

Ambarsih,

// add.cpp : Defines the entry point for the DLL application.

are you sure that you using the C-Compiler and not the c++ compiler?
As much as I know about defaults, that will be a C++ compiled
function, which is something totally different then a C compiled
function. (and, to my knowledge, a C++ function is not easily callable
by PostgreSQL)

Harald

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Massa, Harald Armin wrote:

Ambarsih,

// add.cpp : Defines the entry point for the DLL application.

are you sure that you using the C-Compiler and not the c++ compiler?
As much as I know about defaults, that will be a C++ compiled
function, which is something totally different then a C compiled
function. (and, to my knowledge, a C++ function is not easily callable
by PostgreSQL)

So long as the function uses C linkage (extern "C") it'll be callable
directly from C++ using dlopen(), LoadLibrary, etc.

A C++ function is callable from C via function pointer even if it has
C++ linkage, though the C calling convention declared must handle stack
management, parameter passing and return value popping in the same way
the C++ calling convention on that compiler does. That means that it's
unsafe to call a __thiscall C++ member function from C, but otherwise
it's generally fine so long as the C and C++ compilers default to the
same calling convention or you explicitly specify it on both ends.

--
Craig Ringer

Hello,

I'm new to PostgreSQL and wonder if anyone can help.

I'm creating an after-update-trigger for all tables, which copy the old
records to a backup table. In my test, the table with this trigger has
only two columns - one BIGINT and one VARCHAR.

Also I'd like to pass the backup table's name through a parameter
because I may reuse this function for more than one backup tables.

=====
CREATE OR REPLACE FUNCTION cp_tbl() RETURNS TRIGGER AS $proc$
BEGIN
EXECUTE 'INSERT INTO ' ||
TG_ARGV[0] ||
' SELECT ' ||
OLD;
RETURN NEW;
END;
$proc$ LANGUAGE plpgsql;
=====

At run-time, it prompts an error:

====
ERROR: column "beginning" does not exist
LINE 1: INSERT INTO test_log SELECT (1,BEGINNING)
^
QUERY: INSERT INTO test_log SELECT (1,BEGINNING)
CONTEXT: PL/pgSQL function "cp_tbl" line 2 at EXECUTE statement
====

"beginning" is the actual data I stored in the second column of the table.

I think the issue is related to the use of OLD in the EXECUTE statement.

Does anyone have any idea how to fix it?

Many thanks!!

Nim

On Fri, Oct 23, 2009 at 7:02 AM, Craig Ringer
<craig@postnewspapers.com.au> wrote:

Massa, Harald Armin wrote:

Ambarsih,

// add.cpp : Defines the entry point for the DLL application.

are you sure that you using the C-Compiler and not the c++ compiler?
As much as I know about defaults, that will be a C++ compiled
function, which is something totally different then a C compiled
function. (and, to my knowledge, a C++ function is not easily callable
by PostgreSQL)

So long as the function uses C linkage (extern "C") it'll be callable
directly from C++ using dlopen(), LoadLibrary, etc.

A C++ function is callable from C via function pointer even if it has
C++ linkage, though the C calling convention declared must handle stack
management, parameter passing and return value popping in the same way
the C++ calling convention on that compiler does. That means that it's
unsafe to call a __thiscall C++ member function from C, but otherwise
it's generally fine so long as the C and C++ compilers default to the
same calling convention or you explicitly specify it on both ends.

exactly...also c++ exceptions are incompatible with postgres
exceptions iirc, and it's highly advisable to avoid using threads..
also there are a couple of keyword conflicts that are annoying (those
may have been fixed). those gotchas aside, putting c++ in the backend
is trivially done if you understand difference between c and c++
linkage.

merlin

On Fri, Oct 23, 2009 at 11:27:11AM -0400, Nim Li wrote:

CREATE OR REPLACE FUNCTION cp_tbl() RETURNS TRIGGER AS $proc$
BEGIN
EXECUTE 'INSERT INTO ' ||
TG_ARGV[0] ||
' SELECT ' ||
OLD;
RETURN NEW;
END;
$proc$ LANGUAGE plpgsql;

At run-time, it prompts an error:

Does anyone have any idea how to fix it?

You need to quote your literals! :) The details are a bit fiddly, but
the following thread covered similar things recently:

http://archives.postgresql.org/pgsql-general/2009-09/msg01176.php

--
Sam http://samason.me.uk/

Thank you Sam!!
The code in the posting solves my issue. :)

Nim