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 Programmer’s Supplement.
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.
