Creating a MS-Windows DLL using esql/c for DOS
Note: this is my first posting to netnews.
I am attempting to use Informix esql/c for DOS, release 4.1 to write a
Microsoft Windows Dynamic Link Library to link Windows applications such as
WingZ, Microsoft Excel, or Visual Basic to my database using Informix-net.
I have started with a simple function which executes the $database
statement and returns sqlca.sqlcode. When I call the DLL from Visual Basic
without running remsql, I get error -854, which is as expected. When I run
remsql, load Windows, and call the DLL, I get a general protection fault in
ldllsqlw.dll.
I don't know if I am not allocating memory correctly, using the wrong compiler
command line, or what. Technical support has not been able to help so far.
Does anyone out there have any secrets to share? The Programmers Manual hints
that what I want to do is possible, but offers no clues on how to make it work.
Note: I have compiled and run the wdemo1.ec demo program included with esql/c
without any problem, but I need the flexibilty of a DLL so that I can
use a variety of Windows front ends.
My environment is
Compiler: Microsoft C 6.0
Operating environment: MS-DOS 5.0, MS Windows 3.1 in enhanced mode, QEMM v6.0
Network: AT&T StarGroup
Compiler Command used
esql -wd demo.ec libentry.obj demo.def -o demo.dll
Source Code (demo.ec)
#include <windows.h>
$include sqlwproto.h;
$include sqlca;
/* Prototypes */
long FAR PASCAL start_db();
int FAR PASCAL LibMain(hModule, wDataSeg, cbHeapSize, lpszCmdLine)
HANDLE hModule;
WORD wDataSeg;
WORD cbHeapSize;
LPSTR lpszCmdLine;
{
return 1;
}
/*****************************
FUNCTION: long start_db()
PURPOSE: Open database.
Returns: sqlerror code.
******************************/
long FAR PASCAL start_db()
{
/* Open database */
$ database stores2;
return(sqlca.sqlcode);
}
VOID FAR PASCAL WEP (bSystemExit)
int bSystemExit;
{
return;
}
****************
Definition file (demo.def)
****************
LIBRARY demo
EXETYPE WINDOWS
CODE PRELOAD MOVABLE DISCARDABLE
DATA PRELOAD SINGLE
HEAPSIZE 10240
EXPORTS
WEP @1 RESIDENTNAME
start_db @2