MinGW ODBC Database Programming Errors

[Tim McDonough]

Thanks to suggestions offered here on searching the archives I found
the information I needed on accessing SQL databases using ODBC. I am
still stumped by what I believe is a simple problem with a linker
error.

I am using MinGW on a 32-bit Windows XP machine. I stripped down a
sample program I found to the following code so I could get a single
error to tackle.

==========
#include <windows.h>

#include <sql.h>
#include <sqlext.h>

#include <stdio.h>

SQLHANDLE environment_handle;

SQLRETURN return_code;

int main()
{
  return_code =
    SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE,
&environment_handle);

  return(return_code);
}
==========

My command line is as follows:

    gcc -o tim_odbc.exe -lodbc32 tim_odbc.c

I receive a compiler/linker error that indicates:

  "undefined reference to SQLAllocHandle@12"

The library file is in C:\MinGW\lib\libodbc32.a as I believe it should
be. (I used the installer program from Sourceforge.)

I've seen many, many references to similar link problems with these
reference errors with ODBC but have not yet found any place that
offers an idea on what's being done incorrectly. I'm primarily an
embedded systems programmer and I imagine this is obvious to someone
familiar with MinGW and Windows but that is not me for the past two
days.

Any pointers on what I have done wrong will be greatly appreciated.
Thank you in advance for your patience.

Tim


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[Greg Chicares]

On 2010-01-26 23:15Z, Tim McDonough wrote:
>
> I am using MinGW on a 32-bit Windows XP machine. I stripped down a
> sample program I found to the following code so I could get a single
> error to tackle.

Thank you for taking the trouble to post a simple test case.

>     gcc -o tim_odbc.exe -lodbc32 tim_odbc.c
>
> I receive a compiler/linker error that indicates:
>
>   "undefined reference to SQLAllocHandle@12"

gcc -o tim_odbc.exe tim_odbc.c -lodbc32

http://gcc.gnu.org/ml/gcc-help/2007-02/msg00050.html
|
| The order that you specify things here matters.  The linker examines
| objects from left to right, and hence if something later in the command
| uses a symbol from something that preceded it, the link will fail
| because the linker didn't know that it needed that symbol when it first
| saw the object.  In other words, put things in their dependancy order.
| This usually means "-lfoo" comes last, after all source files.
|
| A lot of people trip this up without ever knowing it, because on ELF
| platforms like Linux there is lazy binding, meaning that symbols can be
| left unresolved at link-time and they will be resolved at runtime by
| ld.so.  This is not the case with PE, where all symbols must be resolved
| at link time, and thus you can't get away with specifying things to the
| linker in the wrong order.

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[Tim McDonough]

On Tuesday, January 26, 2010 6:06 PM [GMT+1=CET],
Greg Chicares wrote:

> On 2010-01-26 23:15Z, Tim McDonough wrote:
>>
>> I am using MinGW on a 32-bit Windows XP machine. I stripped
>> down a sample program I found to the following code so I
>> could get a single error to tackle.
>
> Thank you for taking the trouble to post a simple test case.

I figure if people are using their time to help me out the least I can
do is give them the details of my environment and something to easily
reproduce my problem with as little effort as possible. Hopefully it
will help someone else out by having a complete solution found in some
future search.

Thank you,

Tim


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