"undefined reference" error when compiling extension functions

I am trying to figure out how to write extension functions and I am getting
"undefined reference" errors when I compile on the lines which call "malloc"
and "pfree". How can I get the compiler to see the functions so I can
compile successfully?

I installed PostgreSQL on XP Pro using the windows installer, then I
installed the includes (which are not part of the windows install) by
running the following commands:

configure --without-zlib --includedir=/c/progra~1/postgresql/8.0/include
--with-includes=/c/progra~1/postgresql/8.0/include/port/win32/*

make -C src/include install

Here's the output from make when I try to compile:

$ make makefile filesize.dll

make: Nothing to be done for `makefile'.

gcc -g -I c:/Progra~1/PostgreSQL/8.0/include -I
c:/Progra~1/PostgreSQL/8.0/include/server -I
c:/Progra~1/PostgreSQL/8.0/include/server/port/win32 -I
c:/Progra~1/PostgreSQL/8.0/lib -fpic -c filesize.c

cc1.exe: warning: -fpic ignored for target (all code is position
independent)

gcc -g -I c:/Progra~1/PostgreSQL/8.0/include -I
c:/Progra~1/PostgreSQL/8.0/include/server -I
c:/Progra~1/PostgreSQL/8.0/include/server/port/win32 -I
c:/Progra~1/PostgreSQL/8.0/lib -shared -o filesize.dll filesize.o

filesize.o(.text+0x1a): In function `filesize':

C:/msys/1.0/home/mark/dev/filesize.c:9: undefined reference to
`pg_detoast_datum'

filesize.o(.text+0x3d):C:/msys/1.0/home/mark/dev/filesize.c:11: undefined
reference to `_imp__CurrentMemoryContext'

filesize.o(.text+0x44):C:/msys/1.0/home/mark/dev/filesize.c:11: undefined
reference to `MemoryContextAlloc'

filesize.o(.text+0x9b):C:/msys/1.0/home/mark/dev/filesize.c:19: undefined
reference to `pfree'

filesize.o(.text+0xb1):C:/msys/1.0/home/mark/dev/filesize.c:25: undefined
reference to `pfree'

make: *** [filesize.dll] Error 1

Here's the source I'm trying to compile (taken from PostgreSQL ch 6 by
Douglas and Douglas):

#include "postgres.h"

#include "fmgr.h"

#include <sys/stat.h>

PG_FUNCTION_INFO_V1(filesize);

Datum filesize(PG_FUNCTION_ARGS)

{

text * fileNameText = PG_GETARG_TEXT_P(0);

size_t fileNameLen = VARSIZE( fileNameText ) - VARHDRSZ;

char * fileName = (char *)palloc( fileNameLen + 1 );

struct stat statBuf;

memcpy( fileName, VARDATA( fileNameText), fileNameLen );

fileName[fileNameLen] = '\0';

if( stat(fileName, &statBuf) == 0 && S_ISREG(statBuf.st_mode) )

{

pfree( fileName );

PG_RETURN_INT32((int32)statBuf.st_size);

}

else

{

pfree( fileName );

PG_RETURN_NULL();

}

}

Here's the makefile, from the same example but modified to include the
needed include directories and to output ".dll" file instead of ".so".

# File name: makefile

SERVER_INCLUDES += -I $(shell pg_config --includedir)

SERVER_INCLUDES += -I $(shell pg_config --includedir-server)

SERVER_INCLUDES += -I $(shell pg_config --includedir-server)/port/win32

SERVER_INCLUDES += -I $(shell pg_config --libdir)

CFLAGS += -g $(SERVER_INCLUDES)

.SUFFIXES: .dll

.c.dll:

$(CC) $(CFLAGS) -fpic -c $<

$(CC) $(CFLAGS) -shared -o $@ $(basename $<).o