Using external functions

External functions are functions that are written in languages other than PowerScript and stored in dynamic libraries. External functions are stored in dynamic link libraries (DLLs).

You can use external functions written in any language that supports the standard calling sequence for 32-bit platforms.

If you are calling functions in libraries that you have written yourself, remember that you need to export the functions. Depending on your compiler, you can do this in the function prototype or in a linker definition (DEF) file.

C and C++ compilers typically support several calling conventions, including _cdecl (the default calling convention for C programs), _stdcall (the standard convention for Windows API calls), _fastcall, and thiscall. PowerBuilder, like many other Windows development tools, requires external functions to be exported using the WINAPI (_stdcall) format. Attempting to use a different calling convention can cause an application crash.

When you create your own C or C++ DLLs containing functions to be used in PowerBuilder, make sure that they use the standard convention for Windows API calls. For example, if you are using a DEF file to export function definitions, you can declare the function like this:

LONG WINAPI myFunc()
{
...
};