writing c functions for postgres

Dear Sir

I am trying to build some functions using C language. these functions are

mentioned in the postgresql documentation.

the only function that are work are the one with int32 variable.
the other function bring errors and are not working
any body can give directions

here are the code and the error , i compile them using vc++ 6 and VC++ 2008 and minGW the example below are for minGW

THANKS

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

#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif

/* 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);
}

/* by reference, fixed length */

PG_FUNCTION_INFO_V1(add_one_float8);

Datum
add_one_float8(PG_FUNCTION_ARGS)
{
/* The macros for FLOAT8 hide its pass-by-reference nature. */
float8 arg = PG_GETARG_FLOAT8(0);

PG_RETURN_FLOAT8(arg + 1.0);
}

PG_FUNCTION_INFO_V1(makepoint);

Datum
makepoint(PG_FUNCTION_ARGS)
{
/* Here, the pass-by-reference nature of Point is not hidden. */
Point *pointx = PG_GETARG_POINT_P(0);
Point *pointy = PG_GETARG_POINT_P(1);
Point *new_point = (Point *) palloc(sizeof(Point));

new_point->x = pointx->x;
new_point->y = pointy->y;

PG_RETURN_POINT_P(new_point);
}

/* by reference, variable length */

PG_FUNCTION_INFO_V1(copytext);

Datum
copytext(PG_FUNCTION_ARGS)
{
text *t = PG_GETARG_TEXT_P(0);
/*
* VARSIZE is the total size of the struct in bytes.
*/
text *new_t = (text *) palloc(VARSIZE(t));
VARATT_SIZEP(new_t) = VARSIZE(t);
/*
* VARDATA is a pointer to the data region of the struct.
*/
memcpy((void *) VARDATA(new_t), /* destination */
(void *) VARDATA(t), /* source */
VARSIZE(t)-VARHDRSZ); /* how many bytes */
PG_RETURN_TEXT_P(new_t);
}

PG_FUNCTION_INFO_V1(concat_text);

Datum
concat_text(PG_FUNCTION_ARGS)
{
text *arg1 = PG_GETARG_TEXT_P(0);
text *arg2 = PG_GETARG_TEXT_P(1);
int32 new_text_size = VARSIZE(arg1) + VARSIZE(arg2) - VARHDRSZ;
text *new_text = (text *) palloc(new_text_size);

VARATT_SIZEP(new_text) = new_text_size;
memcpy(VARDATA(new_text), VARDATA(arg1), VARSIZE(arg1)-VARHDRSZ);
memcpy(VARDATA(new_text) + (VARSIZE(arg1)-VARHDRSZ),
VARDATA(arg2), VARSIZE(arg2)-VARHDRSZ);
PG_RETURN_TEXT_P(new_text);
}

the error

in function 'makepoint':
error: 'Point' undeclared (first use in this function)
error: (each undeclared identifier is reported only one
error: for each function it appears in.)
error: 'pointx' undeclared (first use in ´this function)
error: 'pointy' undeclared (first use in his fnction)
error 'new_point' undeclared (first use in his function)
error: syntax error befre ')' oken
in function 'copy text':
error: 'invalid lvalue in assinment
In function 'concat_text'
error: invalid lvalue in assignement
warning no new line at end of file

Please any direction of how to solve the problem

here is the command i wrote in MinGW

gcc -shared -o hamzeh.dll tt1.o -L "c:/programme/postgresql/8.3/lib" -lpostgres

thanks

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