user-defined routines

This topic provides information about how to compile and link a user-defined routine (UDR).

The GLS libraries are already linked to the database server. All HCL® Informix® GLS functions are exported through the SAPI.LIB library. Therefore, you do not need to specify the library explicitly when you compile and link a UDR on Windows™. For example, the following commands compile and link a UDR called func1() that uses the library:

cl /DNT_MI_SAPI /DMI_SERVBUILD
-Id:\msdev\include -Id:\informix\incl\public -Id:\informix\incl
-c func1.c
link /DLL /OUT:func1.dll /DEF:func1.def func1.obj d:\informix\lib\SAPI.LIB

In the preceding example, d: specifies the drive on which Informix® software is installed; informix is the directory that INFORMIXDIR specifies. The resulting dynamic link libraries (DLLs) must have the READONLY attribute set with the attrib +r command.

The Microsoft™ compiler, cl, defaults to the /MT option, which specifies the multithreaded library for DLL builds. This multithreaded library is statically linked to the DLL. You can specify the /MD option to put MSVCRT40.DLL in a command path. All the UDRs that are built with /MD use one copy of the LIBC DLL. This option prevents virtual-memory buildup in the database server when many UDRs are loaded.

The following example shows the use of the /MD option to compile the func1() UDR:

cl /MD /DNT_MI_SAPI /DMI_SERVBUILD \
-Id:\msdev\include -Id:\informix\incl\public -Id:\informix\incl
-c func1.c

If MSVCRT40.DLL is not visible to the database server, the database server puts the following error in the online.log file when it attempts to execute the UDR:

Error loading UDR

On UNIX™ platforms, the GLS libraries are not linked to the database server. Therefore, you must explicitly specify the location and name of the library, as you do for client applications.

The location of the header file, ifxgls.h, is the $INFORMIXDIR/incl/public directory. This directory contains many of the other files that a client application uses. Make sure that you include this directory with the -I option of the compiler.

Additionally, you need to indicate that the module is a UDR (which runs on the server computer), not a client application (which runs on a client computer). Include the MI_SERVBUILD compiler flag when you compile a UDR.

The following example builds a shared object called udrs.so that contains the C code for a UDR called func1():

% cc -KPIC -DMI_SERVBUILD -I$INFORMIXDIR/incl/public -I$INFORMIXDIR/incl
-L$INFORMIXDIR/esql/lib -c func1.c
% ld -G func1.o -o udrs.so