All of an application’s Client-Library and CS-Library callbacks must be declared with CS_PUBLIC. On some platforms (such as Windows), a compiler may use one of many calling conventions for functions in generated code. A function’s calling convention determines how the machine registers and the machine stack are manipulated when the function is called. The compiler generates different machine instructions for different calling conventions. CS_PUBLIC (along with any required compiler options) ensures that the application’s callbacks are compiled with the same calling convention with which Client-Library invokes them.
Compiler options are described in the Open Client and
Open Server Programmers Supplement for Microsoft
Windows or the Open Client and Open Server Programmers
Supplement for UNIX.
On many platforms, CS_PUBLIC is defined such that it adds nothing to a function declaration. On these platforms, applications that declare callbacks with CS_PUBLIC behave no differently than those that omit CS_PUBLIC. However, for portability, CS_PUBLIC should be used to declare callbacks on any platform.
